SYSTEMATICS OF THE GRACILARIACEAE (GRACILARIALES ... · of a two-celled carpogonium branch, 2) a supporting cell producing other two to three two-celled sterile ﬁlaments, 3) the

SYSTEMATICS OF THE GRACILARIACEAE (GRACILARIALES, RHODOPHYTA): ACRITICAL ASSESSMENT BASED ON rbcL SEQUENCE ANALYSES1

Carlos Frederico D. Gurgel2 and Suzanne Fredericq

University of Louisiana at Lafayette, Department of Biology, Lafayette, Louisiana 70504-2451, USA

Generic concepts in the economically importantagarophyte red algal family Gracilariaceae wereevaluated based on maximum parsimony, Bayesianlikelihood, and minimum evolution analyses of thechloroplast-encoded rbcL gene from 67 specimensworldwide. The results confirm the monophyly ofthe family and identify three large clades, one ofwhich corresponds to the ancestral antiborealgenera Curdiea and Melanthalia, one to Gracilar-iopsis, and one to Gracilaria sensu lato, which con-tains nine distinct independent evolutionary lineages,including Hydropuntia. The species currently at-tributed to Hydropuntia comprise a single well-supported clade composed of two distinct lineages.The two most basal clades within Gracilaria sensulato deserve generic rank: a new genus centeredaround G. chilensis Bird, McLachlan et Oliveira andG. aff. tenuistipitata Chang et Xia and a resurrectedHydropuntia encompassing primarily Indo-Pacific(G. urvillei [Montagne] Abbott, G. edulis [S. Gmelin]P. Silva, G. eucheumatoides Harvey, G. preissiana[Sonder] Womersley, and G. rangiferina [Kutzing]Piccone) and western Atlantic species (G. cornea J.Agardh, G. crassissima P. et H. Crouan in Maze etSchramm, G. usneoides [C. Agardh] J. Agardh, G.caudata J. Agardh, and G. secunda P. et H. Crouan inMaze et Schramm). Cystocarpic features within theGracilaria sensu lato clades appear to be morephylogenetically informative than male characters.The textorii-type spermatangial configuration is rep-resented in two distinct clusters of Gracilaria. TherbcL genetic divergence among the Gracilariaceaegenera ranged between 8.46% and 16.41%, provid-ing at least 2.5 times more genetic variation thandoes the 18S nuclear rDNA. rbcL also resolvesintrageneric relationships, especially within Graci-laria sensu lato. The current number of gracila-riacean species is underestimated in the westernAtlantic because of convergence in habit andapparent homoplasy in vegetative and reproductiveanatomy.

Key index words: Bayesian; Gracilaria; Gracilaria-ceae; Hydropuntia; maximum parsimony; phylo-geny; rbcL; Rhodophyta; systematics

Abbreviations: BP, bootstrap proportions; G., Graci-laria; Gp., Gracilariopsis; ITS, internal transcribedspacer; ME, minimum evolution; MP, maximumparsimony; PP, Bayesian posterior probabilities;SSU, small subunit

The Gracilariales comprises a recently describedorder of marine red algae (Fredericq and Hommer-sand 1989a) based on the Gracilariaceae Nageli (1847),a family previously placed in the Gigartinales (Kylin1932, 1956). Members are characterized by the fol-lowing: 1) a female reproductive apparatus composedof a two-celled carpogonium branch, 2) a supportingcell producing other two to three two-celled sterilefilaments, 3) the fertilized carpogonium fusing with itssupporting cell to form the fusion cell, 4) the cells of thesterile filaments fusing and transfer their cellular-richcontents into the fusion cell, and 5) the gonimoblastsdeveloping directly and primarily outward from thefusion cell (Fredericq and Hommersand 1989a, 1990b,Hommersand and Fredericq 1990). Studies targetingthe higher evolutionary relationships among red algaebased on molecular analyses confirm the monophyly ofthe Gracilariales (Freshwater et al. 1994, Fredericqet al. 1996).

The order is composed of a single family, Gracilar-iaceae, because the status of the parasitic Pterocladio-philaceae is still unresolved by molecular methods.Generic concepts within the Gracilariaceae have beenbased on anatomical details in cystocarp ontogeny thatreflect strategies for the provision of nutrients by thegametophyte to the developing carposporophyte(Fredericq and Hommersand 1990b). Currently, theGracilariaceae is composed of up to seven genera(Fredericq and Hommersand 1990b), namely GracilariaGreville (1830), Hydropuntia Montagne (1842), Mel-anthalia Montagne (1843), Curdiea Harvey (1855),Gracilariophila Setchell et Wilson in Wilson (1910),Gracilariopsis Dawson (1949), and Congracilaria Yama-moto (1986). Identification keys and short diagnosesfor each genus are provided in Fredericq and Hom-mersand (1990b). Curdiea and Melanthalia are restrictedto the temperate regions around southern Australia,Tasmania, and New Zealand; the former is also found

1Received 23 August 2002. Accepted 18 September 2003.2Author for correspondence and present address: Universidade

Federal do Rio de Janeiro, CCS, Instituto de Biologia, Departamento deBotanica, Ilha do Fundao, Rio de Janeiro, RJ, Brasil, 21941-900.e-mail [email protected].

138

J. Phycol. 40, 138–159 (2004)r 2004 Phycological Society of AmericaDOI: 10.1046/j.1529-8817.2004.02129.x

in Antarctica. Curdiea is characterized by a thick foliosehabit and a high degree of morphological plasticity.

Considered synonymous with Gracilaria are Coral-lopsis Greville (1830) and Tyleiophora J. G. Agardh(1890). Polycavernosa Chang et Xia (1963) has beensubsumed into Hydropuntia (Wynne 1989). Morpholo-gically and genetically Curdiea and Melanthalia areconsidered distinct genera from each other and fromthe remaining Gracilariaceae (Fredericq and Hom-mersand 1989a,b,c, 1990a,b, Bird et al. 1992). Althoughsome authors consider Gracilaria (hereafter G.), Graci-lariopsis (hereafter Gp.), and Hydropuntia distinct genera(Wynne 1989, 1998), others consider Hydropuntia asynonym of Gracilaria (Abbott et al. 1991, Bellorin et al.2002), and still others place all three genera insynonymy with Gracilaria (Gargiulo et al. 1992, Abbott1995, 1999). The proposed synonymy between Graci-laria and Gracilariopsis is based on practical taxonomicconsiderations (Abbott 1999) instead of true phyloge-netic uncertainties, because there has been overwhelm-ing morphological and genetic evidence supportingthe separation of these two genera (Fredericq andHommersand 1989a,b, Bird et al. 1992, Bellorin et al.2002). Nonetheless, the precise taxonomic identifica-tion of sterile cylindrical specimens remains a difficulttask, especially in cases of morphological modificationdue to the influence of particular biotic (e.g. herbivory)and abiotic (e.g. drifting habit, wave exposure, sandscours) factors. In these cases, vegetative characters ofcylindrical species from both genera often converge.

Subgenera within Gracilaria are based on the shapeof the mature spermatangial conceptacle: the textoriitype, the verrucosa type, and the Hydropuntia type (sensuYamamoto, 1978). However, distinguishing subgeneraon such a basis is said to be unreliable because severalspecies display features characteristic of more than onesubgenus (Abbott et al. 1991, Schneider and Searles1991, Gargiulo et al. 1992).

Whereas all genera but Gracilaria are relativelysmall, comprising fewer than 20 species each, Gracilariahas nearly 300 described species, of which 110 arecurrently recognized worldwide (Oliveira and Plastino1994). At present, the genus Gracilaria is the majorsource of agar and the third largest farmed seaweedworldwide (Zemke-White and Ohno 1999). Propelledby an economic interest in phycocolloids, the study ofGracilaria has resulted in numerous proposals for tax-onomic and nomenclatural changes (Silva et al. 1996).After a very confused and dynamic lectotypificationhistory (nomenclatural reviews in Fredericq and Hom-mersand 1989a, Steentoft et al. 1991, Silva 1994, Bird1995, Irvine and Steentoft 1995, Silva et al. 1996),Gracilaria was officially typified with G. compressa (C.Agardh) Greville 1830 (Greuter et al. 2000:168); thisname is a synonym of G. bursa-pastoris (S. Gmelin) Silva(1952:265).

In addition to morphological features, molecularand caryological studies have also been applied to solvetaxonomic and systematic problems within the Graci-lariaceae. Chromosome counts, reported so far only for

some species of Gracilaria and Gracilariopsis, reveal thatthese two genera have distinct chromosome numbers(24 and 32, respectively), corroborating that these twogenera are indeed distinct taxonomic entities (Kapraun1993, Kapraun et al. 1993). However, this technique hasno resolution below the generic level and has nothelped to solve systematic questions below the level ofgenus. Chromosome counts for the remaining Graci-lariaceae genera did not provide reliable results (Hydro-puntia, Kapraun et al. 1993) or have not been assessed(Curdiea and Melanthalia).

Allozyme profiles have been used only to infergenetic variation at population level within a singlespecies, Gracilaria chilensis, from New Zealand (Intasu-wan et al. 1993). The authors found population struc-ture despite the fact that intrapopulation variation(heterozygosity) and genetic distance among NewZealand G. chilensis populations are low. Allozymeprofiles have not been applied to resolve broad-scalesystematic questions in red algae because this techniquehas limited applications and is more suitable for studiesat, and especially below, the species level.

Restriction maps (RFLP) and primer-DNA similarityrandom amplified polymorphic DNA (RAPD) hasbeen more widely used to address systematic questionsin the Gracilariaceae. RAPD has been successfullyapplied to infer intraclonal genetic variation withinand among populations, strains, and coalesced versusnoncoalesced thalli in G. chilensis (Gonzalez et al. 1996,Santelices et al. 1996, Meneses and Santelices 1999).RFLPs of isolated plastid DNA have also been success-fully applied to infer the potential usefulness of thistechnique (Goff and Coleman 1988) in red algalsystematics. The RFLP pattern generated upon theelectrophoretic separation of digestion fragmentsshowed that within Gracilariopsis andersonii (as Gracilar-iopsis lemaneiformis), patterns are identical among popu-lations spread 2000 miles along the western NorthAmerica coast but not between higher taxa. Eventhough Goff and Coleman (1988) showed that thismolecular technique can distinguish different generaand species, only one Gracilariopsis and two Gracilariaspecies were used in their study. RFLPs of specificallychosen PCR-amplified markers were applied to inferpopulation differences between Chilean and NewZealand populations of Gracilaria chilensis (internaltranscribed spacer [ITS], Candia et al. 1999) and toassess species limits within Gracilaria and Gracila-riopsis (18S rDNA, Scholfield et al. 1991). Both studiesincluded small numbers of species, the former target asingle species, and the latter, two species (Gp. longissimaand G. gracilis [as ‘‘G. verrucosa’’]) from different parts ofthe world. Microsatellite primers, a codominant marker,have been developed for Gracilariaceae, but thistechnique, besides being developed for a single species,G. gracilis, focuses on inferring population level ques-tions and proved to be able to identify individuals withina population (Wattier et al. 1998, Luo et al. 1999).

DNA sequence analysis has been the most reliablyand widely used molecular technique to infer phylo-

SYSTEMATICS OF THE GRACILARIACEAE 139

genic relationships at the species level within theGracilariaceae. These studies have used regions ofthe nuclear ribosome cistron (Bird et al. 1992, 1994,Goff et al. 1994, Bird 1995), the chloroplast encodedrbcL gene (Gurgel et al. 2003a,b), and the rbcL-rbcSspacer region (Goff et al. 1994). In the Gracilariaceaethese studies have 1) identified new Gracilariopsisspecies (Gurgel et al. 2003a,b), 2) showed that world-wide distributed species are indeed artificial assem-blages of distinct taxa (e.g. the ‘‘G. verrucosa’’ and Gp.lemaneiformis species complexes) (Bird et al. 1994, Goffet al. 1994), and 3) provided new insights aboutcorrelations between molecular and morphologicalphylogenetic relationships (Bird et al. 1992, 1994, Bird1995, Bellorin et al. 2002). All these DNA sequencestudies produced strong evidence supporting thetaxonomic distinctiveness of the genera Curdiea, Graci-laria, Gracilariopsis, and Melanthalia, but the position ofthe genus Hydropuntia remains controversial. Despitethese advances in the systematics of the Gracilariaceae,all molecular techniques applied so far have focused ononly a few species (e.g. G. chilensis, G. gracilis, G.tenuistipitata, G. tikvahiae, Gp. longissima, Gp. lemaneifor-mis) and were geographically restricted (mostly NorthAmerica, Atlantic Europe, Chinese, and Chileanspecies). The most extensive phylogenetic surveys pub-lished to date are provided by Bird et al. (1992) andBellorin et al. (2002) in which 19 and 39 Gracilariaceae18S rDNA sequences were analyzed, respectively.Unfortunately, the 18S rDNA provides insufficientresolution at the species level in the Gracilaria/Hydro-puntia complex (Bird 1995:263, Bellorin et al. 2002,fig. 1B). The two ITS of the ribosomal cistron have pro-ven useful in distinguishing between some closelyrelated congeners. However, the level of genetic var-iation is too great to allow unambiguous alignment ofsequences among most species within the generaGracilaria or Gracilariopsis, let alone between genera(Bird et al. 1994, Bellorin et al. 2002). Therefore ITScannot be used for determining phylogenetic relation-ships in the family as a whole (Bird 1995).

In this study, the rbcL is considered to provideoptimal resolution for inferring species level phyloge-netic relationships within the Gracilariaceae, relative toother commonly used genetic markers (18S, ITS1,5.8S, ITS2, and 28S rDNA regions). The main goal ofthis study is to use rbcL sequence data to provide acritical assessment of generic and subgeneric conceptsand to resolve species-level phylogenetic and biogeo-graphic questions pertaining to the Gracilariaceae.This study is the most extensive systematic survey andphylogenetic analysis of the Gracilariaceae with mole-cular data performed to date.

MATERIAL AND METHODS

Silica-gel dried specimens and extracted DNA samples weredeposited in the Seaweed Laboratory at the University ofLouisiana at Lafayette and stored at � 201 C. DNA sampleswere prepared using the DNeasy Plant Mini Kit (Qiagen,

Valencia, CA, USA) or were submitted to a CTAB-cesiumchloride DNA procedure (Freshwater and Rueness 1994).Plastid-encoded rbcL was selected to infer a phylogeny for theGracilariaceae. PCR (FrbcLstart-R753, F57-R753, F577-R1381,F993-RrbcSstart) and sequencing primers (FrbcLstart, F7, F57,F492, F577, F753, F993, R753, R1105, R1381, RrbcSstart)used in this study are listed in Freshwater and Rueness (1994)and Gavio and Fredericq (2002). Protocols for gene amplifica-tion, automated sequencing, and multiple sequence alignmentare identical to those given in Lin et al. (2001). Voucherspecimens and materials for morphological studies were fixedand stored in 5% formalin/seawater and/or pressed asherbarium sheets and deposited in the Herbarium of theUniversity of Louisiana at Lafayette. Herbarium abbreviationsfollow those of Holmgren et al. (1990). Species identificationswere based on the original descriptions, critical analysis ofpublished literature, and on the type method (Silva 1952). Anextensive photographic collection of type species of Gracilar-iaceae housed in Herbarium of the University of Louisiana atLafayette was used to match recently collected specimens.

Partial and complete rbcL sequences were produced for atotal of 67 specimens of Gracilariaceae (Table 1) comprising 3Curdiea, 4 Melanthalia, 13 Gracilariopsis, and 47 Gracilaria sensulato specimens (Gracilaria sensu lato, as defined by Abbott et al.[1991], includes all species once placed in Hydropuntia). DNAsequences have been deposited in GenBank (Benson et al.1994). GenBank accession numbers, species identification andauthors, and information concerning origin, date, and collectorare listed in Table 1. The generated sequence data werecompiled and aligned with Sequencher (Gene Codes Corp.,Ann Arbor, MI, USA) and MacClade 4.0 (Maddison andMaddison 2000) and exported for phylogenetic analysis.Because some sequence data were incomplete at the 50

terminus of the coding region in many taxa, the data set wasrestricted to the last 1368 base pairs (bp) of the 1467-bp rbcL.

Phylogenetic analyses were conducted with maximumparsimony (MP) and minimum evolution (ME) as implementedin PAUP* v.4.0 beta 10 (Swofford 2002), and the Bayesianlikelihood as implemented in MrBayes 1.11 (Huelsenbeck andRonquist 2001). Parsimony trees obtained under the Fitchcriterion of equal weights for all substitutions (Fitch 1971) wereinferred in a two-part heuristic search scheme, excludinguninformative characters. Initial searches designed to increasethe likelihood of swapping within the ‘‘island’’ of trees leadingto the most parsimonious solution (Maddison 1991) consistedof 5000 random sequence additions holding 25 trees at eachstep, MULPARS, and tree-bisection-reconnection algorithmswith MULTREES (saving multiple trees) and STEEPESTDESCENT options. All most parsimonious trees found in thisinitial search were then swapped to completion using the tree-bisection-reconnection algorithm. Consistency and retentionindices were calculated (Farris 1989, Kluge and Farris 1989).

The optimal model of sequence evolution to fit the dataalignment estimated by hierarchical likelihood ratio testsperformed by Modeltest v.3.04 (Posada and Crandall 1998)was the GTR IþG (general time reversible model withinvariable sites and gamma distribution). The parameters usedwere as follows: assumed nucleotide frequencies A50.3475;C50.1202; G50.1556; T50.3767; substitution rate matrixA–C substitutions51.0663, A–G56.4763, A–T50.7696, C–G51.7148, C–T511.5115, G–T51.0; proportion of sitesassumed to be invariable50.5445; and rates for variable sitesassumed to follow a gamma distribution with shape para-meter51.2152. These likelihood parameters were applied inBayesian [Lset Nst56 revmat5 (1.0663, 6.4763, 0.7696,1.7148, 11.5115, 1.0) rates5 invgamma shape51.2152ncat54 basefreq5 estimate;] and ME analyses.

For the Bayesian analysis, we ran four chains of the MarkovChain Monte Carlo, sampling 1 tree every 10 generations for

CARLOS FREDERICO D. GURGEL AND SUZANNE FREDERICQ140

64/62

10 changes

G. beckeri SOUTH AFRICAG. capensis SOUTH AFRICA

G. viellardii TAIWANG. spinulosa TAIWANG. sp. PHILIPPINES

G. textorii JAPANG. flabelliforme VENEZUELA

G. occidentalis LA, USAG. ornata PANAMA

G. apiculata VENEZUELAG. domingensis BRAZILG. cervicornis FL, USA

G. curtissiae VENEZUELAG. multipartita FRANCE

G. bursa-pastoris ITALYG. tikvahiae CANADA

G. lacinulata VENEZUELAG. damaecornis FL, USA

G. hayi FL, USAG. hayi PANAMAG. galetensis PANAMAG. oliveirarum VENEZUELA

G. smithsoniensis PANAMAG. mammillaris LA, USA

G. yoneshigueana BRAZILG. intermedia VENEZUELAG. venezuelensis FL, USAG. gracilis ENGLANDG. gracilis FRANCE

G. pacifica WA, USAG. canaliculata PHILIPPINESG. salicornia PHILIPPINES

G. arcuata PHILIPINES

G. secunda FL, USA

G. usneoides MEXICOG. crassissima PANAMA

G. cornea VENEZUELAG. caudata FL, USA

III

G. edulis PHILIPPINESG. preissiana AUSTRALIA

G. rangiferina GHANAG. rangiferina PHILIPPINES

G. eucheumatoides PHILIPPINESG. urvillei AUSTRALIA

II

G. aff. tenuistipitata JAPANG. aff. tenuistipitata VA, USA

G. chilensis CHILE98/74

Gracilaria sensu lato

Major Clade

I New Genus

Hydropuntia

IV

IX

Gracilaria sensu stricto

VIII

64/62

Gp. tenuifrons GUADELOUPEGp. cata-luziana MEXICO

Gp. sp. NAMIBIA

Gp. longissima ITALYGp. longissima ENGLAND

Gp. sp. AUSTRALIA

Gp. lemaneiformis PERUGp. costaricensis COSTA RICA

Gp. carolinensis NC, USAGp. andersonii OR, USA

Gp. hommersandii PANAMAGp. sp. CHINA

Gp. heteroclada PHILIPPINES

Gracilariopsis Major Clade

65/7992/96

71/85

56/-

95/10069/65

M. concinna AUSTRALIAM. intermedia AUSTRALIA

M. obtusata AUSTRALIAM. abscissa NEW ZEALAND

C. racovitzae ANTARCTICAC. coriacea NEW ZEALAND

C. crassa NEW ZEALAND

Curdiea + Melanthalia Major Clade

Rhodymenia pseudopalmataGrateloupia doryphora

Pachymenia carnosaOutgroup

V

VI

VII

-/51

-/54

95/97

94/98

93/96

78/64

-/88

-/57

92/95

99/99

95/98

76/-

73/80

50/-

98/98

96/94

100/98

84/8587/79

53/5478/69

97/100

-/52

98/96

81/-

83/9799/99

97/9785/88

74/98

FIG. 1. One of 36 most parsimonious trees from analysis of the rbcL gene sequence data of the family Gracilariaceae (treelength5 2805 steps, consistency index50.293, retention index50.6421, number of phylogenetically informative characters5 490).Numbers above the branches correspond to bootstrap proportion values (%) from maximum parsimony and minimum evolutionanalyses, respectively (5MP/ME, both based on 1000 resamplings) and thick bold branches correspond to 100% bootstrap proportionvalues obtained in both phylogenetic methods (5100/100). Roman numerals correspond to (nine) distinct evolutionary lineages(5 subgroups) within the genus Gracilaria sensu lato, as also seen in Figure 2A.


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a;co

ll.

B.

Wys

or,

6M

arch

19

99

AY

04

935

1,

98

.0%

Gracilariahayi

Gu

rgel

,F

red

eric

qet

J.N

.N

orr

isH

utc

hin

son

Is.

bea

chcl

ose

toF

ort

Pie

rce

jett

y,F

ort

Pie

rce,

FL

,U

SA

;co

ll.

C.

F.G

urg

el,

Oct

ober

19

98

AY

04

931

9,

95

.6%

Gracilariahayi

Gu

rgel

,F

red

eric

qet

J.N

.N

orr

isG

alet

aP

oin

t,C

olo

nC

ity,

Pan

ama;

coll.

B.

Wys

or,

21

Sep

tem

ber

19

99

AY

04

931

5,

98

.1%

Gracilaria

curt

issi

aeJ.

Ag

ard

hM

agu

eL

loro

so,

Pen

insu

laP

arag

uan

a,F

alco

nS

tate

,V

enez

uel

a;co

ll.

C.

F.G

urg

el,

13

July

19

99

AY

04

932

7,

98

.4%

Gracilariadamaecornis

J.A

gar

dh

Bea

chb

ehin

dth

eH

arb

or

Bra

nch

Oce

ano

gra

ph

icIn

stit

uti

on

jett

y,F

ort

Pie

rce,

FL

,U

SA

;co

ll.

C.

F.G

urg

el,

13

July

19

98

AY

04

932

6,

10

0%

Gracilariadomingensis

So

nd

erex

Ku

tzin

gP

raia

Ras

a,B

uzi

os

city

,R

iod

eJa

nei

roS

tate

,B

razi

l;co

ll.

C.

F.G

urg

el,

12

Dec

ember

199

8A

Y0

49

37

1,

98

.6%

Gracilariaedulis

(Gm

elin

)S

ilva

Lit

tle

San

taC

ruz,

Ph

ilip

pin

es,

coll.

L.

M.

Lia

o,

28

Ap

ril

19

98

AY

04

938

7,

98

.6%

Gracilariaeucheumatoides

Har

vey

Tam

bu

li,

Ceb

u,

Ph

ilip

pin

es;

coll.:

S.

M.

Lin

;1

8A

pri

l1

998

AY

04

938

9,

93

.3%

Gracilariaflabelliform

isco

mb

.n

ov.

(P.

etH

.C

rou

anin

Maz

eet

Sch

ram

m)

Gu

rgel

etF

red

eric

q

Pla

yaB

arra

nq

uit

a,P

uer

toC

um

areb

oar

ea,

Fal

con

Sta

te,

Ven

ezu

ela;

coll.

C.F

.G

urg

el,

14

July

19

99

AY

04

934

3,

98

.8%

Gracilariagaletensis

Gu

rgel

,F

red

eric

qet

J.N

.N

orr

isG

alet

aP

oin

t,A

tlan

tic

Pan

ama;

coll.

B.

Wys

or,

20

Jun

e1

99

9A

Y0

49

32

0,

97

.3%

Gracilariagracilis

(Sta

ckh

ou

se)

Ste

ento

ft,

Irvi

ne

etF

arn

ham

W.

An

gle

Bay

,W

ales

,E

ng

lan

d;

coll.

M.

H.

&F.

Ho

mm

ersa

nd

,2

2Ju

ly1

99

7A

Y04

94

00

0,

98

.0%

Gracilariagracilis

(Sta

ckh

ou

se)

Ste

ento

ft,

Irvi

ne

etF

arn

ham

Ile

Ver

te,

Ro

scoff

,B

ritt

any,

Fra

nce

;co

ll.

J.C

abio

ch,

22

Jun

e1

99

3A

Y04

93

39

9,

98

.0%

Gracilariainterm

edia

J.A

gar

dh

Pu

erto

Esc

on

did

o,

Pen

insu

laP

arag

uan

a,V

enez

uel

a;co

ll.

C.

F.G

urg

el,

13

July

19

99

AY

04

933

6,

97

.6%

Gracilarialacinulata

(Vah

l)H

ow

eL

aE

ncr

uci

jad

a,P

enin

sula

Par

agu

ana,

Fal

con

Sta

te,

Ven

ezu

ela;

coll.

C.

F.G

urg

el;

13

July

199

9A

Y0

49

34

4,

97

.1%

Gracilariamam

millaris

(Mo

nta

gn

e)H

ow

ein

Bri

tto

nO

ffsh

ore

LA

,U

SA

;co

ll.

C.

F.G

urg

el&

S.

Frd

eric

q,

26

May

20

00

AY

04

932

3,

97

.1%

Gracilariamultipartita

(Cle

men

t)H

arve

yC

aran

tec,

Bri

ttan

y,F

ran

ce;

coll.

J.C

abio

ch,

22

May

200

0A

Y0

49

32

2,

98

.6%

Gracilariaoccidentalis

(B�r

gen

sen

)B

od

ard

Off

shore

LA

,U

SA

;co

ll.

C.

F.G

urg

el&

S.

Fre

der

icq

,2

6M

ay2

000

AY

04

932

2,

98

.6%

Gracilariaornata

Are

sch

ou

gF

ort

Ran

do

lph

,C

olo

nci

ty,

Pan

ama;

coll.

B.

Wys

or,

26

Feb

ruar

y1

99

9A

Y0

49

31

8,

92

.9%

Gracilariapacifica

Ab

bo

ttIn

dia

nIs

lan

d,

WA

,U

SA

;co

ll.

M.

H.

Ho

mm

ersa

nd

AY

04

939

7,

97

.7%

Gracilariapreissiana

(So

nd

er)

Wo

mer

sley

inM

in-T

hei

net

Wo

mer

sley

Cer

van

tes,

Au

stra

lia;

coll.

M.

H.

&F.

H.

Ho

mm

ersa

nd

,2

0S

epte

mb

er1

995

AY

04

940

3,

93

.7%


En

tity

Co

llec

tio

nd

ata

Gen

Ban

kac

cess

ion

nu

mb

eran

dp

erce

nt

sequ

ence

d

Gracilariarangiferina

(Ku

tzin

g)

Pic

con

eT

ern

a,G

han

a;co

ll.

G.

Am

eka,

leg

.M

.H

.H

om

mer

san

d,

Mar

ch2

00

1A

Y04

93

79

,8

6.0

%Gracilariarangiferina

(Ku

tzin

g)

Pic

con

eL

aV

ista

del

Mar

,u

pp

erC

alar

ian

,Z

amb

oan

ga

Cit

y,P

hilip

pin

es;

coll.

S.M

.L

in;

27

Ap

ril

199

8A

Y04

93

80

,9

5.5

%Gracilariasalicornia

(C.

Ag

ard

h)

Daw

son

Su

lpa,

Ceb

u,

Ph

ilip

pin

es;

coll.

S.

M.

Lin

,1

9A

pri

l1

99

8A

Y04

93

85

,9

8.0

%Gracilariasecunda

P.et

H.

Cro

aun

inS

chra

mm

etM

aze

Tam

pa

Bay

,F

L,

US

A;

coll.

C.

Daw

es,

26

Oct

ob

er1

99

9A

Y04

93

60

,9

7.8

%

Gracilaria

sp.

Bu

lusa

n,

Sou

thL

uzo

n,

Ph

ilip

pin

es;

coll.

S.

M.

Lin

,2

1A

pri

l1

998

AY

04

93

84

,9

3.2

%Gracilariasm

ithsoniensis

Gu

rgel

,F

red

eric

qet

J.N

.N

orr

isG

alet

aP

oin

t,A

tlan

tic

Pan

ama;

coll.

B.

Wys

or,

BW

#7

37

,2

0Ju

ne

199

9A

Y04

93

21

,9

7.3

%

Gracilariaspinulosa

(Okam

ura

)C

han

get

Xia

Tai

wan

;co

ll.

S.

M.

Lin

,1

1M

ay1

99

8A

Y04

93

95

,9

3.3

%

Gracilariaaff.tenuistipitata

Ch

ang

etX

iaT

ok

awa,

Jap

an;

coll.

M.

Yo

shiz

aka,

7Ju

ne

19

93

AY

04

93

24

,9

7.3

%

Gracilariaaff.tenuistipitata

Ch

ang

etX

iaH

og

Isla

nd

Bay

,E

aste

rnS

hore

,V

A,

US

A;

coll.

C.

Tyl

er,

10

Feb

ruar

y1

99

9,

leg

.T

.F

ran

ko

vich

AY

04

93

12

,9

8.0

%Gracilariatextorii

(Su

rin

gar

)D

eT

on

iG

ob

og

ahan

a,Ja

pan

;1

0Ju

ly1

99

4,

leg

.M

.H

om

mer

san

dA

Y04

93

25

,9

7.5

%Gracilariatikvahiae

McL

ach

lan

Mo

rret

po

nd

,Po

mqu

eth

arb

or,

An

tig

on

ish

Co

.,N

ova

Sco

tia,

Can

ada;

coll.C

.J.

Bir

d,3

July

199

9A

Y04

94

34

,9

7.0

%Gracilariaurvillei

(Mo

nta

gn

e)A

bb

ott

inA

bb

ott

,Z

han

get

Xia

Lee

Po

int,

Dar

win

,A

ust

ralia;

coll.

M.

H.

Ho

mm

ersa

nd

,2

2N

ove

mb

er1

99

5A

Y04

94

02

,9

7.4

%

Gracilariausneoides

(C.

Ag

ard

h)

J.A

gar

dh

San

taR

osa

lia

bri

dg

e,C

amp

ech

eB

ay,

Mex

ico

;co

ll.

C.

F.G

urg

el,

14

Feb

ruar

y1

99

9A

Y04

93

46

,9

8.0

%Gracilariavenezuelensis

Tay

lor

Ind

ian

Riv

er,

Fo

rtP

ierc

e,F

L,

US

A;

coll.

C.

F.G

urg

el,

Oct

ob

er1

99

8A

F53

96

03

,9

5.4

%Gracilariaviellardii

Silva

Tai

wan

;co

ll.

S.

M.

Lin

,2

2A

pri

l1

998

AY

04

93

94

,9

5.5

%Gracilariaoliveirarum

Gu

rgel

,F

red

eric

qet

J.N

.N

orr

isL

aV

ela

de

Co

ro,

Fal

con

Sta

te,

Ven

ezu

ela;

coll.

C.

F.G

urg

el,

13

July

19

99

AY

04

93

30

,9

1.8

%

Gracilariayoneshigu

eana

Gu

rgel

,F

red

eric

qet

J.N

.N

orr

isP

rain

ha

bea

ch,

Arr

aial

do

Cab

oC

ity,

Rio

de

Jan

eiro

Sta

te,

Bra

zil;

coll.

A.

Tao

uil,

13

Mar

ch1

99

8A

Y04

93

72

,9

3.4

%

Gracilariopsisan

dersonii

(Gru

no

w)

Daw

son

Sea

lR

ock

,L

inco

lnC

o.,

Ore

go

n,

US

A;

coll.

S.

Fre

der

icq,

15

May

19

99

AY

04

94

14

,9

6.4

%Gracilariopsiscarolinensis

Lia

o&

Hom

mer

san

din

Gu

rgel

,L

iao

,F

red

eric

q&

Ho

mm

ersa

nd

Ku

reB

each

,F

ort

Fis

her

,N

C,

US

A;

coll.

D.

W.

Fre

shw

ater

,1

4A

pri

l1

99

1A

Y04

94

12

,9

6.7

%

Gracilariopsiscata-luzian

aG

urg

el,

Fre

der

icq

&N

orr

is1

91

03

.31

’N

�9

61

0.4

4’W

,V

era

Cru

zar

ea,

Mex

ico

;co

ll.

C.

F.G

urg

el;

10

Feb

ruar

y1

999

AY

04

94

06

,8

0.2

%

Gracilariopsiscostaricensis

Daw

son

So

uth

end

,P

laya

Tam

arin

do

,N

ico

yaP

enn

insu

la,

Gu

anac

aste

,C

ost

aR

ica;

coll.

D.

T.

Tal

bo

t&

D.

W.

Fre

shw

ater

,1

7M

arch

19

99

AY

04

94

23

,9

8.4

%

Gracilariopsisheteroclada

(Zh

ang

etX

ia)

Zh

ang

etX

iain

Ab

bo

ttD

apd

ap,

Bu

lusa

n,

Lu

zon

,P

hilip

pin

es;

coll.

S.

M.

Lin

,2

2A

pri

l1

99

8A

Y04

94

11

,9

1.1

%

Gracilariopsishommersandii

Gu

rgel

,F

red

eric

q&

Norr

isF

ort

Ran

do

lph

,C

olo

nC

ity,

Pan

ama;

coll.

B.

Wys

or,

26

Mar

ch1

998

AY

04

94

05

,9

7.1

%

Gracilariopsisleman

eiform

is(B

ory

)D

awso

n,

Acl

eto

etF

old

vik

Yac

illa

,P

aita

,P

iura

,P

eru

;co

ll.

C.

Acl

eto

&R

.Z

un

iga,

3M

arch

199

4A

Y04

94

15

,9

7.6

%

Gracilariopsislongissima

(Sta

ckh

ou

se)

Irvi

ne,

Ste

ento

ftet

Far

nh

amV

enet

ian

lag

oo

n,

Ad

riat

icS

ea,

Ital

y;co

ll.

K.

S.

Co

le,

7S

epte

mber

19

98

AF

52

78

81

,9

7.5

%

Gracilariopsislongissima

(Sta

ckh

ou

se)

Irvi

ne,

Ste

ento

ftet

Far

nh

amO

ffS

and

foot

Cas

tle,

Po

rtla

nd

Har

bo

ur,

Do

rset

,E

ng

lan

d;

coll.

Wm

.F

arn

ham

&M

.S

teen

toft

,3

0A

ug

ust

19

92

,le

g.

C.

J.B

ird

;A

Y04

94

20

,9

7.3

%

Gracilariopsis

sp.

Lak

eB

utl

er,

Ro

be,

Au

stra

lia;

coll.

H.

B.

S.

Wo

mer

sley

,3

Mar

ch1

995

AY

04

94

22

,9

7.8

%Gracilariopsis

sp.

Sw

akop

smu

nd

,N

amib

ia;

coll.

M.

H.

Ho

mm

ersa

nd

,6

July

19

93

AY

04

94

10

,9

8.2

%Gracilariopsis

sp.

Qin

gd

ao,

Sh

and

on

gP

rov.

,C

hin

a;co

ll.

M.

H.

Hom

mer

san

d,

23

Ap

ril

19

94

AY

04

942

1,

65

%Gracilariopsistenuifrons

(Bir

det

Olive

ira)

Fre

der

icq

etH

om

mer

san

dIl

etC

aret

,G

uad

elo

up

e,F

ren

chW

est

Ind

ies;

coll.

A.

Ren

ou

x,

2D

ecem

ber

19

93

AY

04

94

18

,9

7.8

%

Melan

thalia

abscissa

(Tu

rner

)H

oo

ker

&H

arve

yN

ewZ

eala

nd

;co

ll.

W.

Nel

son

,2

5A

pri

l1

99

4A

Y04

94

28

,9

7.9

%

Melan

thalia

concinna

J.A

gar

dh

War

rnam

bo

ol,

Au

stra

lia;

coll.

M.

H.

Ho

mm

ersa

nd

,1

3Ju

ly1

99

5A

Y04

94

29

,9

6.1

%Melan

thalia

interm

edia

Har

vey

War

rnam

bo

ol,

Au

stra

lia;

coll.

M.

H.

Ho

mm

ersa

nd

,1

3Ju

ly1

99

5A

Y04

94

30

,9

7.9

%Melan

thalia

obtusata

(Lab

illa

rdie

re)

J.A

gar

dh

War

rnam

bo

ol,

Vic

tori

a,A

ust

ralia;

coll.

M.

H.

Ho

mm

ersa

nd

,1

3Ju

ly1

99

5A

Y0

49

43

1,

99

%

TA

BL

E1

.(continued

)


1,000,000 generations starting with a random tree. Stationaritywas reached at above generation 20,200. Thus, the first 20,200generations were the ‘‘burn in’’ of the chain, and inferencesabout the phylogeny were based on those trees sampled afterthe burn in point. A 50% consensus tree (majority rule asimplemented by PAUP*) was computed from the 98,981 treessaved after the burn in point. Reliability of the Bayesianconsensus tree is given by the frequency at which each nodeappears among all saved trees after the burn in generation.This frequency corresponds to the true probability of the clades(Hall 2001).

ME was performed using a heuristic search of 1000replications, holding 10 trees each stepwise addition step,with a tree-bisection-reconnection swapping algorithm, MUL-TREES and STEEPEST DESCENToptions. Starting trees wereobtained via stepwise addition with a random sequenceaddition and a random nine digits starting seed (586366). Amaximum likelihood distance correction was used and set withthe GTR substitution rate matrix parameters listed above,excluding invariable sites and the gamma distribution. The MEmethod only recovered the most probable hypothesis similar tothose given by the MP and Bayesian methods when simplermodels of sequence evolution were applied (data not shown).Support for nodes in the MP and ME analyses were assessed bycalculating bootstrap proportion (BP) values (Felsenstein 1985)based on 1000 resamplings.

Mutational saturation of third codon positions in rbcL wasexamined by plotting all pairwise genetic distances uncorrectedfor multiple substitutions (‘‘p’’ distance) against those correctedfor multiple substitutions with Kimura-2 parameter (Kimura1980), according to the procedure in Daugbjerg and Andersen(1997) in which for all pairwise combinations, corrected anduncorrected values for multiple substitutions were calculatedfor first/second positions only and third codon positions only.

Sequences of Rhodymeniaceae (Rhodymenia pseudopalmata)and Halymeniaceae (Grateloupia doryphora and Pachymeniacarnosa) were selected as the outgroup based on phylogenetichypotheses derived from earlier global analyses of the Flor-ideophycidae as a whole (Fredericq et al. 1996). Pairwise geneticdistances were calculated based on uncorrected percentages,‘‘p’’ distances (Table 2).

RESULTS

No insertion or deletion mutations were found inthe rbcL sequences, permitting unambiguous align-ment of all sequences. Tree lengths of 100,000 ran-domly generated trees had a skewed distribution (g15

�0.5708, Po0.01), indicating the presence of nonran-dom structure (Hillis and Huelsenbeck 1992, Hilliset al. 1993).

TABLE 2. Comparisons of Gracilariaceae genetic diversity between rbcL and 18S rDNA (SSU) sequences.

rbcL (this study) SSU (Bellorin et al. 2002)

IntergenericCurdiea vs. Melanthalia 14.13–15.40 1.47Gracilaria sensu lato vs. Gracilariopsis 8.45–11.84 2.24–4.65CurdieaþMelanthalia vs. Gracilariopsis 14.44–16.41 3.65–6.35

Proposed new intergeneric divisionsSubgroup I vs. Gracilaria sensu stricto 10.01–13.05 (n53) —Subgroup II vs. Gracilaria sensu stricto 12.31–8.46 (n56) —Subgroup III vs. Gracilaria sensu stricto 9.91–6.71 (n55) —

InterspecificCurdiea 11.79–16.20 (n53) —Melanthalia 0.14–8.70 (n54) —Gracilariopsis 2.37–7.47 (n513) 0.47–2.88Gracilaria sensu lato 2.00–13.61 (n547) 0.00–1.29Gracilaria subgroup I 12.12–12.67 (n53) —Gracilaria subgroup II 4.22–10.08 (n56) —Gracilaria subgroup III 0.40–4.18 (n55) —Gracilaria sensu stricto (5 subgroups IV–IX) 2.10–9.05 (n533) —

Intraspecifica

Gracilariopsis 0.00–0.07 0.18Gracilaria sensu stricto 0.00–1.89 0.00–0.41

Genetic divergence expressed as uncorrected percentages (%, ‘‘p’’ distances). Gracilaria sensu lato as defined by Abbott et al. (1991)to include Hydropuntia. Gracilaria sensu lato subgroups composed of subgroup I, G. chilensis þ G. aff. tenuistipitata; subgroup II,G. urvillei, G. eucheumatoides, G. edulis, G. preissiana and G. rangiferina; subgroup III, G. crassissima, G. cornea, G. caudata, G. secunda,G. usneoides.

arbcL data used to compute intraspecific genetic distances from Gurgel et al. (2001).

FIG. 2. Gracilariaceae phylogeny based on rbcL DNA sequences. (A) Majority rule consensus of 97,991 trees sampled according to aBayesian MCMC tree sampling procedure (number of generations5106, burning point520,200, evolutionary model5GTRþ IþG).Numbers above the branches correspond to Bayesian posterior probability support, and thick bold branches correspond to 100%Bayesian posterior probability. Curdiea and Melanthalia monophyletic clade is in yellow, the Gracilariopsis clade in pink, and species fromthe genus Hydropuntia complex in gray. Roman numerals correspond to distinct evolutionary lineages (5 subgroups) within the genusGracilaria sensu lato. (B–J) transverse sections of Gracilaria sensu lato reproductive structures. (B–E) Reproductive morphological featurescharacteristic of species from Gracilaria sensu stricto only (subgroups IV–IX). (F–H) Reproductive morphological features characteristic ofthe genus Hydropuntia (subgroups II and III). (I and J) Reproductive morphological features characteristic of a new genus (subgroup I).(B, C, F, I) Spermatangial conceptacles. (B) Textorii type (G. ‘‘blodgettii’’, reproduced from Terada and Yamamoto 2000). (C) Verrucosa type(from G. gracilis). (F) Hydropuntia type (from G. crassissima). (I) chilensis type (G. chilensis, reproduced from Bird et al. 1990). (D, E, G, H, J)Cystocarps with different carposporophyte designs. (D) G. flabelliforme, (E) G. tikvahiae, (G) G. crassissima, (H) G. edulis, (J) G. aff.tenuistipitata from USA.

"



Among the 1368 bp in the data set (excludingoutgroup sequences), 561 are constant and 807 vary (ofwhich 490 are phylogenetically informative). Informa-tive and noninformative variable sites, regardless ofcodon position, were evenly distributed throughoutthe gene (data not shown) with an overall averagetransition/transversion rate of 2.289. (A larger than 1.0transition/transversion rate is expected because amongsingle-step substitutions in the universal genetic code ata third codon position, only 3% of the transitions causeamino acid replacements compared with 41% for trans-versions [Wakeley 1996]). The translated amino aciddata set (not shown) is less variable than the DNAsequence data set and does not provide phylogeneticresolution. No evidence of widespread saturation ispresent among the first and second codon positions (datanot shown), but saturation was observed in nucleotidesites at the third codon position that differ in pairwisedistance comparisons between evolutionarily distant taxa(data not shown). Even though some nucleotides at thirdcodon position are saturated, they contributed to thebiggest number of informative sites in the data set (79%)compared with the first (17%) and second (about 4%)codon positions.

Comparisons between published 18S rDNA (smallsubunit [SSU]) sequences (Bird et al. 1992) and therbcL sequences used in this study reveal a greaterphylogenetic signal in rbcL (35.81%5490/1368 bp,n567 taxa) than in SSU rDNA (6.86%5119/1734 bp,n519 taxa) in the Gracilariaceae. The overall geneticvariation displayed by these two markers also showsthat rbcL has more variation than SSU, and the lowestgenetic values of intergeneric distances for rbcL aretwice as large as those for SSU rDNA (Table 2). AmongGracilaria sensu lato species, the smallest distance islarger than the largest value in SSU rDNA (Table 2).

MP analyses resulted in 36 equally most parsimo-nious trees of 2805 steps (tree length), consistencyindex50.293 and retention index50.6421. The MPphylogram presented (Fig. 1) is the one among all 36most parsimonious trees that presents the highest like-lihood value (–ln515362.054) under the best evolu-tionary model found by the hierarchical likelihoodratio test. ME analysis resulted in 23 minimum treeswith an ME score52.085450 (data not shown). Theoverall majority rule consensus topology given by theBayesian analysis is fully resolved and well supported,

with the exception of G. textorii and G. sp. from thePhilippines (Fig. 2A).

All three phylogenetic analyses identified threemajor assemblages (Figs. 1 and 2A): a Curdiea/Melantha-lia clade, a Gracilariopsis clade, and a Gracilaria sensu latoclade (including Hydropuntia). In the Gracilaria sensu latoclade, nine distinct evolutionary lineages (subgroups)were also identified (Figs. 1 and 2A): a G. chilensis/G. aff.tenuistipitata clade (subgroup I); a G. urvillei clade(subgroup II); a G. caudata/G. crassissima clade (sub-group III); a G. gracilis /G. pacifica clade (subgroup IV);a G. arcuata/G. salicornia clade (subgroup V); a G. vene-zuelensis/G. intermedia clade (subgroup VI); a G. mam-millaris clade (subgroup VII); a G. tikvahiae/G.damaecornis clade (subgroup VIII); and, the mostderived lineage, the G. bursa-pastoris/G. textorii clade(subgroup IX) (Figs. 1 and 2A).

A strict consensus of the 36 most parsimonious treesresulted in a fully resolved tree except for the presenceof two polytomies: one at the deeper nodes of the threemost derived subgroups within Gracilaria sensu latoclade (subgroups VI, VIII, and IX), for which boot-strap support is low (BP575%) to lacking (Fig. 1), andthe other at the position of Gp. sp. from Namibia withinGracilariopsis. The strict consensus of the 23 ME treesresulted in a less resolved phylogram when comparedwith the MP consensus, with polychotomous nodes atthe three most basal species in Gracilariopsis, Gp. sp.from Namibia, Gracilaria subgroup I (G. chilensis), andat the basal nodes among Gracilaria subgroups III to Vand among subgroups VI to IX (data not shown).Major inconsistencies among the MP and ME phylo-grams pertain to the position of G. textorii, G. multi-partita, and G. bursa-pastoris within Gracilaria sensu latosubgroup IX; the position of Gracilaria sensu latosubgroup VIII; the position of Gp. sp. from Namibia;and the two most basal species in Gracilariopsis. In all 36most parsimonious trees, Gracilaria sensu lato subgroupsII and III form a monophyletic clade without bootstrapsupport (Fig. 1); however, high support for the sametopology was obtained in the Bayesian tree (PP599%,Fig. 2A). Only ME did not cluster these subgroupstogether (data not shown). The Bayesian tree (Fig. 2A)has the same topology as the MP tree (Fig. 1) except forthe position of subgroups VI and VII that in the MPtree (Fig. 1) appears inverted: subgroup VI at a morederived position than subgroup VII. In both trees

TABLE 3. Comparative morphological differences of textorii-type spermatangial conceptacle between the Gracilaria chilensis/G. aff. tenuistipitata and G. bursa-pastoris/G. textorii lineages.

Spermatangial characters Subgroup I G. chilensis lineage Subgroup IX G. textorii lineage

Cortical cells Elongated, as in Gracilariopsis Variable: isodiametric, rounded,squarish, or elongated

Cortical cells flanking spermatangia Club shaped, wide Linear to obovoid, thinConceptacle in transverse section Squarish ConcaveSpermatangial parent cell layer Restricted to floor of

conceptacle onlySurrounding entire internal surface

Three-dimensional shape ofnoncoalesced conceptacles

Well shaped Bow shaped


(Figs. 1 and 2A), however, the internal node leading tosubgroup VII received high support (BP598%,PP591%), making this phylogenetic difference themost striking one between the results from these twophylogenetic methods. Detailed characterization ofmore derived relationships will be treated in thediscussion of each Gracilaria sensu lato subgroup.

Comparisons between rbcL molecular phylogenies(Figs. 1 and 2A) and morphological characters of malereproductive structures within the Gracilaria sensu latoclade revealed two independent origins for the textoriitype of spermatangial conceptacles (Yamamoto 1978):one at Gracilaria sensu lato subgroup I and the other atGracilaria sensu lato subgroups VI–IX. A reexaminationof the spermatangial conceptacles from these twodistinct monophyletic groups revealed stable morpho-logical differences (Table 3).

DISCUSSION

Although it was previously shown that the Gracilar-iales is a monophyletic order as inferred fromchloroplast-encoded rbcL and nuclear-encoded 18SSSU rDNA and 28S large subunit rDNA sequenceanalyses (Fredericq et al. 1996, Harper and Saunders2001), phylogenetic information is published thatclarifies the generic concepts within the order, espe-cially within Gracilaria. The most recent and compre-hensive phylogenetic study based on DNA sequenceanalysis of the Gracilariaceae is given by Bellorin et al.(2002) using 36 SSU rDNA sequences. Of SSU rDNA,large subunit rDNA, and rbcL, rbcL sequences show thehighest genetic variation (Freshwater et al. 1999) in theGelidiales. ITS rDNA sequences in the Gracilariaceaeare alignable only among closely related species,whereas alignments among distant species are limitedonly to specific regions presumed constrained by secon-dary structures (Bird 1995, Bellorin et al. 2002). SSUrDNA sequences among distinct species are sometimesidentical and not sufficiently variable to differentiatebetween closely related species, producing low boot-strap support and equivocal relationships (Bellorinet al. 2002). In contrast, rbcL DNA sequences in theGracilariaceae revealed higher levels of interspecificgenetic diversity (Table 2), especially within Gracilariasensu lato, enabling us to detect not only interspecificrelationships among closely related species but alsopopulation structure among a sample of haplotypeswithin a species (Gurgel and Fredericq 2000, Gurgelet al. 2001). Major clades and subgroups within theGracilariaceae are discussed below along with phylo-geographic and morphological remarks.

Curdiea and Melanthalia major clade. The generaCurdiea and Melanthalia form a monophyletic groupendemic to the antiboreal regions, well supported inMP and ME analyses (BP5 100 in both) and mod-erately supported in the Bayesian analysis (PP5 75%)(Figs. 1 and 2A). These two genera share morpholo-gical features supportive of their alliance, including acystocarp cavity completely filled with gonimoblasts

and carposporangia formed in long straight chains(Fredericq and Hommersand 1989c, 1990a,b). Mel-anthalia differs from Curdiea by having dark, linear,narrow thalli with distinct subdichotomous branches,a prominent apical zone composed of a thick multi-cellular meristematic cortex, and sterile thick-walledgonimoblasts in the cystocarp (Fredericq and Hom-mersand 1990a,b, Womersley 1996). In all MP (Fig.1) and ME (not shown) results, C. racovitzae, a speciesendemic to the Antarctic Peninsula, appears as sisterto the genus Melanthalia, rendering Curdiea para-phyletic in excluding the former genus. However, inthe Bayesian tree (Fig. 2A), C. racovitzae is placed backin Curdiea, rendering both genera monophyletic andsister to each other. Recent vegetative and reproduc-tive morphological analyses of extensive collection ofC. racovitzae, made by Dr. R. Moe and deposited in UC(e.g. UC#1557573, UC#1557575), reveal that thisspecies corresponds better to the genus Curdiea.

Three of four Melanthalia species included in thisstudy, M. abscissa, M. concinna, and M. obtusata, arereported from southern Australia. The first wasoriginally described from New Zealand and the lattertwo from Australia. Womersley (1996), although recog-nizing all three species, pointed out that morphologicalsimilarities among them might warrant their treatmentas varieties of the same species. The phylogeneticresults herein indicate that despite vegetative andreproductive similarities, M. abscissa is geneticallydistinct from the other two species (Figs. 1 and 2A).

The rbcL data set presented in this study indicatesthat uncorrected pairwise genetic distances (‘‘p’’ distance)between two haplotypes from the same species rangebetween zero and 1.5%. Morphologically distinct andwell-defined species usually have values equal to orgreater than 2%. Species whose ‘‘p’’ distances liebetween 1.5% and 2.0% often require further systema-tic analysis before a final taxonomic conclusion can bemade. Between M. concinna and M. obtusata there is a1.65% pairwise ‘‘p’’ distance, and our phylogeneticresults (tree topologies) support the recognition of twodistinct species. Melanthalia abscissa is reported to havedistinctly compressed branches, mostly 0.7–1.3 mmbroad, whereasM. concinnahas terete to slightly compres-sed mostly 0.3–0.8 mm broad branches (Womersley1996, p. 31). A fourth species, M. intermedia, wasoriginally described as M. obtusata var. intermediaHarvey (1858), but Womersley (1996) merged it withM. abscissa. The rbcL sequence of M. intermedia wasnearly identical to that of M. concinna (0.14%), sug-gesting that these two species are conspecific. Mel-anthalia abscissa is the only species of the genus reportedfrom New Zealand (Adams 1994), and the inclusion ofnew rbcL haplotypes of M. abscissa from Australia couldreveal geographic isolation among New Zealand andAustralian populations.

Gracilariopsis major clade. The genus Gracilariopsishas been well characterized morphologically (Freder-icq and Hommersand 1989b, Steentoft et al. 1995,Gurgel et al. 2003b) and genetically (Goff and Cole-


man 1988, Kapraun 1993, Kapraun et al. 1993, Birdet al. 1994, Goff et al. 1994, Gurgel et al. 2003a,c).The present phylogenetic analysis also confirms themonophyly of the genus (Figs. 1 and 2A).

Gurgel et al. (2003c) provided an rbcL phylogeny ofGracilariopsis and reinstated the generitype,Gp. sjoestedii(Kylin) Dawson, to include plants distributed fromVancouver, British Columbia to Pacific California,Mexico, and the name was corrected to Gp. andersonii.Gracilariopsis lemaneiformis was shown not to have aworldwide distribution but to be restricted to thevicinity of Peru in South America, with Gp. costaricensisfrom Costa Rica most likely being the same species.Gracilariopsis carolinensis, a new species from NorthCarolina (Gurgel et al. 2003c), is related to Gp.lemaneiformis and Gp. costaricensis. Entities that havebeen referred to as Gp. lemaneiformis from China andJapan constitute an undescribed species that occupies abasal position in association with Gp. heteroclada fromthe Philippines (Figs. 1 and 2A). Gracilariopsis tenuifronsfrom the Caribbean sea is identified as a distinct sisterspecies to Gp. cata-luziana, a species so far endemic tothe southwestern Gulf of Mexico. Gracilariopsis long-issima is recognized from Western Europe. An unde-scribed species from Namibia and an unidentifiedinvasive species from the Gulf of California, Mexico,and South Australia are represented in a clade thatincludes Gp. longissima from Europe. Three new speciesfor the northwestern Atlantic Ocean, Gp. silvanaGurgel, Fredericq et Norris from Venezuela, Gp.hommersandii Gurgel, Fredericq et Norris from Vene-zuela and Panama, and Gp. cata-luziana Gurgel,Fredericq et Norris from the Mexican Gulf of Mexicowere recently described (Gurgel et al. 2003a). Gracilar-iopsis silvana is the first confirmed flat Gracilariopsisspecies, a genus currently characterized by only cylin-drical species.

Gracilaria sensu lato major clade. Gracilaria, themost species-rich genus in the Gracilariaceae and oneof the most taxonomically difficult genera in theRhodophyta, comprises at least nine distinct evolu-tionary lineages (Figs. 1 and 2A). The phylogeneticrelationships among deeper nodes within the mostderived Gracilaria lineage (subgroup IX, Figs. 1 and2A) are not resolved in MP phylograms (Fig. 1) andreceived the lowest values of phylogenetic support inthe Bayesian tree (Fig. 2A). This lineage is composedof smaller clades with variable degrees of phyloge-netic support that include the generitype G. bursa-pastoris. This subgroup is characterized by flat-foliosespecies with textorii-type spermatangial conceptacles.

There is a stronger correlation between thallusshape and type of spermatangial conceptacle thanbetween female and male reproductive features (Ya-mamoto 1984), with a tendency for cylindrical speciesto either display a verrucosa- (deep pits) or chorda-type(superficial) spermatangial arrangement and for flat,compressed, and foliose species to be of the textorii type(shallow pits). Major evolutionary trends among the 43distinct Gracilaria species recognized in the data set

emerge. The five most basal Gracilaria sensu lato sub-groups (I–V) are characterized mainly by cylindricalspecies; exceptions such asG. crassissima andG. eucheuma-toides possess a range of phenotypic variation thatextends from totally cylindrical to compressed habits.Only G. rangiferina and G. preissiana among the 17species in this assemblage are characterized by exclu-sively flat thalli. In contrast, the four most derivedsubgroups (VI–IX) are composed mainly of flat species.Twenty-seven of the 31 species in these four subgroupsare flat, one (G. tikvahiae) displays both phenotypes,and three have cylindrical to slightly compressed thalli(G. damaecornis, G. venezuelensis, and G. bursa-pastoris).These results suggest that the cylindrical habit is theplesiomorphic condition in Gracilariopsis and Gracilariasensu lato.

Subgroup I—the Gracilaria chilensis complex: Thefirst divergent clade within Gracilaria sensu lato is com-posed of G. chilensis from Chile and G. aff. tenuistipitatafrom Japan and Virginia, USA. This assemblageshares several cystocarp characters with Gracilariopsis,such as the lack of multinucleated tubular nutritivecells linking gonimoblasts to the pericarp and agradual morphological transition between gonimo-blasts and mature carposporangia (Fig. 2J) (Birdet al. 1986, 1990, Nelson and Ryan 1991).

Both species typically inhabit protected estuarineenvironments. Specimens newly identified as G. aff.tenuistipitata collected from the east coast of the UnitedStates possess cystocarp features that are remarkablysimilar to those found in G. chilensis and G. aff.tenuistipitata from Tokawa, Japan. The low pairwisegenetic distance between the Japanese and U.S. speci-mens (0.88% bp) suggests that the G. aff. tenuistipitata isa non-native introduction in the northwest Atlanticfrom Japan. The species seems to be spreading innorthern Europe ( J. Rueness, University of Oslo,personal communication), consistent with the generaltrend of numerous Asiatic invaders in European andNorth American Atlantic waters as a result of aqua-culture introductions (Ribera and Boudouresque 1995,Maggs and Stegenga 1999, Gavio and Fredericq 2002).

Subgroup I, so far, is characterized exclusively bycylindrical and irregularly branched Pacific and Indo-Pacific species with a textorii-type spermatangial con-ceptacle (Fig. 2I). The non-Pacific terete counterpart,G. bursa-pastoris, has proved to be part of a separateevolutionary lineage (subgroup IX). Our resultssuggest that the textorii type of spermatangial concep-tacle arose at least twice in the evolutionary history ofGracilaria sensu lato (Table 3, Fig. 2, B and I). It is likelythat additional Asian cylindrical species with textorii-type spermatangial pits are part of this complex andthat future inclusion of DNA sequences from those taxa(e.g. G. chouae Zhang et Xia, G. minuta Lewmanomont,and G. parvispora Abbott) should confirm this hypoth-esis. Future critical examination and comparative ana-lysis of spermatangial development between G. chilensisandG. bursa-pastoris/G. textoriimay reveal further develop-mental differences not discernible in mature stages.


The reproductive characters of G. chilensis and G. aff.tenuistipitata (Fig. 2, I and J) are sufficiently differentfrom the type ofGracilaria for these species to be elevatedto generic rank. This observation was formulatedpreviously by Nelson and Ryan (1991).

Subgroup II—Pacific Hydropuntia: This clade in-cludes only Indo-Pacific species to date. The typespecies of Hydropuntia (G. urvillei [Montagne] Abbottin Abbott et al. [1991]) is found in this clade (Figs. 1and 2A). The name Hydropuntia has priority overPolycavernosa Chang et Xia (G. edulis [S. Gmelin]P. Silva 1952) (Wynne 1989). All members of this cladepossess diagnostic features that correspond to thegeneric concept of Hydropuntia, such as the develop-ment of deeply embedded, often confluent, sperma-tangial conceptacles of subcortical-medullary originthat produce spermatangia in clusters (Chang andXia 1963, Xia and Abbott 1985, 1987). Xia and Abbott(1987) considered the distinct cystocarp ontogenydescribed for G. crassissima (Fredericq and Norris1985, Fredericq and Hommersand 1990b) as theHydropuntia type. Subgroup II does not containG. cornea and G. crassissima, species previously group-ed and currently placed in Hydropuntia (Wynne 1998).The latter two species are part of a distinct clade (sub-group III). However, both MP (Fig. 1) and theBayesian analysis (Fig. 2A) places species with Hydro-puntia-like reproductive characters (Fig. 2, F–H)within a monophyletic clade of the genus Gracilaria,with varying support (MP, no support; Bayesian,PP5 99%). The reproductive features that character-ize this clade are different enough from those foundin the type of Gracilaria for the species in thisassemblage to be elevated together with subgroupIII to generic rank, as a Hydropuntia.

Subgroup III—Atlantic Hydropuntia: This sub-group thus far includes only western Atlantic species.All species are typically cylindrical, with G. crassissimasometimes displaying a compressed prostrate thallus.Gracilaria secunda is a validly published species thathas been considered a synonym of G. cornea (Taylor1960, as G. debilis). Our phylogenetic results supportthe recognition of this species distinct from G. corneaand sister to G. caudata. There is a striking morpho-logical similarity between G. caudata and G. secunda.The morphological plasticity within each of these twospecies is huge and overlaps, making their taxonomicdelineation problematic. Nevertheless, two distinctgenetic entities do exist, and the type of G. secunda isthe best match to the specimens used in this study.

Gracilaria usneoides is phylogenetically closer toG. crassissima than to G. cornea (Figs. 1 and 2A), butmorphologically G. cornea and G. usneoides are muchalike. Fredericq and Norris (1985) provided an accountof the development of reproductive features ofG. crassissima from Belize and demonstrated its dis-tinctness in terms of an elaborate reticulate postferti-lization fusion cell and origin of male reproductiveparent cells. A reinterpretation of the photographs ofG. caudata in Plastino and Oliveira (1997) reveals that

carposporophyte development is of the same type asthat of G. crassissima, even though a few upper tubularnutritive cells are depicted. The sexual reproductivestructures of G. secunda are still unknown. It is clearfrom the current study that there are two distinctevolutionary lineages encompassing the concept ofHydropuntia.

Because subgroups II and III form a well-supportedmonophyletic group (Fig. 2A) and the type species ofHydropuntia is found in this clade (H. urvillei), all thespecies pertaining to these two subgroups are, in thisstudy, transferred to Hydropuntia (see below for newcombinations).

Subgroup IV—the G. salicornia complex: Gracilariacanaliculata, G. crassa Harvey ex J. Agardh (1876), andCorallopsis opuntia J. Agardh (1872) were consideredconspecific by Newton (1953). The first two specieswere subsumed into G. salicornia by Xia (1986) andMeneses and Abbott (1987), who independently cameto the same conclusion (Abbott 1988). However, Silvaet al. (1996) recognize both G. canaliculata and G.salicornia as distinct species.

In this lineage, the morphological variation displayedby species with cylindrical and constricted thalli corre-sponds to a phenotypic continuum from one speciesdescription to the next, which makes species delineationimpossible based solely on morphological grounds.Abbott (1988) mentioned that plants of G. canaliculataor G. crassa could be placed in any of those proposednames. The molecular results obtained in this study,however, do not support the conspecificity of G. sali-cornia and G. canaliculata. RbcL-based phylogenetic treesshow that these two species are related but taxonomi-cally distinct (Figs. 1 and 2A) (genetic distance based onrbcL is 5.35%). The future inclusion of sequences fromG. cacalia ( J. Agardh) Dawson (1954, p. 2), G. crassaHarvey ex J. Agardh (1876, p. 417), and othermorphologically similar species is necessary to resolvethe taxonomic status of this species complex, which ischaracterized by some degree of constrictions in theirterete thalli and verrucosa type of spermatangia.

The presence of distinct constrictions at the nodaland internodal regions were once used to create thegenus Corallopsis J. Agardh 1876, which includedG. urvillei (as Hydropuntia urvillei) and the 11 namescurrently in synonym with G. salicornia (Xia 1986,Abbott 1988). Thallus constriction grades from almostnonexistent (e.g. G. canaliculata) to very pronounced(e.g. G. salicornia). When comparing plants with div-ergent morphologies (e.g. with or without constric-tions), the identification is clear but in many cases thereis a phenotypic continuum between distinct pheno-types among specimens in the same population.Dawson (1954) concluded that nodal constrictionsmay not define genera and placed Corallopsis in syno-nymy with Gracilaria. The presence of some degree ofthalli constrictions and the presence of only verrucosatype of spermatangial conceptacles characterize thishighly polymorphic lineage. Although characteristic ofthis species complex, the pattern of thallus constriction


is not shared by all members of this clade, whichincludes G. arcuata, with strong bootstrap support. Theplacement of G. urvillei in a distinct separate clade(Gracilaria subgroup II) is evidence that sharp con-strictions at the base of branches arose more than oncein Gracilaria, increasing the degree of morphologicalhomoplasy. However, the thallus constriction patternand habit of G. urvillei are different from that found inspecies of this G. salicornia lineage. All members of thisclade for which reproductive characters are knownhave cystocarp structures typical of Gracilaria sensustricto (sensu Fredericq and Hommersand 1990b) (Fig.2, D and E). Corallopsis is not supported by rbcL seq-uence analysis as generically distinct from GracilariaGreville. All members of this subgroup are character-ized by having verrucosa type of spermatangial con-ceptacles (Fig. 2C) that do not develop into theHydropuntia type (Fig. 2F).

Subgroup V: Gracilaria gracilis and G. pacifica form awell-supported clade based on rbcL sequence analysis(BP5 100%, in both MP and ME results; PP5 100%),and their genetic distance is 4.47%. Currently,G. gracilis is the only terete species of Gracilariadescribed for the flora of the northeastern Atlantic(excluding the Mediterranean). The genetic distancebetween the southern U.K. G. gracilis haplotype andthe northern France specimen included in the dataset is not large enough (0.95%) to suggest that thesetwo populations are distinct species. The ontogeny ofreproductive structures of G. gracilis (as G. verrucosa[Hudson] Papenfuss) was used as the reference todefine the order Gracilariales (Fredericq and Hom-mersand 1989a). All members of this subgroup arecharacterized by having verrucosa type of spermatan-gial conceptacles (Fig. 2C) that do not develop intothe Hydropuntia type (Fig 2F).

Subgroup VI—the Gracilaria mammillaris complex:Morphologically, this is one of the most problematiclineages in the genus Gracilaria. The overall habit ofmembers of this subgroup show remarkable simila-rities, especially when dealing with atypical pheno-types and small specimens. In other parts of theworld, phenotypic plasticity and striking morpholo-gical similarities among flat Gracilaria species alsoproduce similar taxonomic problems (e.g. G. textorii)(Yamamoto 1984). This subgroup is composedentirely of foliose dichotomously branched speciesrestricted to the western Atlantic that are oftenmisidentified as G. mammillaris. The current conceptof G. mammillaris corresponds indeed to a speciescomplex. Morphological comparisons among phylo-genetic distinct populations (based on rbcL phyloge-nies) and type specimens revealed that at least fourspecies were new and have been recently described:G. galetensis, G. hayi, G. oliveirarum, and G. smithso-niensis, (Gurgel et al. 2003b). Sterile specimens of G.galetensis may have commonly been misidentifiedas Rhodymenia pseudopalmata. The expansion of sys-tematic surveys of flat Gracilaria species in theCaribbean may reveal an even greater number of

new species currently passing under the name ofG. mammillaris.

SubgroupVII: This is a well-supported group com-posed of only poorly known western Atlantic species.All specimens examined have a distinct habit:G. intermedia (Venezuela) and G. yoneshigueana (Brazil)are flat, whereas G. venezuelensis has terete to slightlycompressed thalli (Taylor 1942). More extensivecollections of fertile members of this clade arenecessary before a full characterization of their reprod-uctive structures can be accomplished. Since itsdescription, G. venezuelensis has been cited only twicein floristic surveys: one record from the Mexican Gulfof Mexico (Dreckmann and Perez-Hernandez 1994)and the other from the Philippines (Westernhagen1973, 1974). Reports of this species outside thewestern Atlantic should be considered tentative,because it is unlikely that southeastern Asia and theCaribbean share Gracilaria species that were notartificially introduced. In the western Atlantic,G. venezuelensis seems to be common but not recog-nized and often presents as thin cylindrical and verybranched phenotypes when growing as drifting matsat protected environments such as bays and the U.S.intracoastal waterways (e.g. Tampa Bay, westernFlorida, and the Indian River, eastern Florida; C. F.Gurgel, personal observation). When growing at-tached to subtidal rocky substrata (e.g. Capron Shoal,Fort Pierce Co., FL, USA), G. venezuelensis develops amore robust, thicker, and regular dichotomousbranched phenotype. Gracilaria yoneshigueana is adelicate 7-cm-long flat endemic species from Brazil,so far collected only in the Rio de Janeiro state,occurring in exposed as well as protected intertidalrocky shores (Gurgel et al. 2003b).

Subgroup VIII—The Gracilaria tikvahiae clade: Thisclade is composed of the western Atlantic speciesG. damaecornis and G. tikvahiae and the poorly definedG. lacinulata. All species are restricted to the westernAtlantic with the exception of G. tikvahiae, which hasbeen introduced in Hawaii (Abbott 1999, p. 216). Allspecies in this subgroup display a persistent largepostfertilization fusion cell (Fig. 2E). Gracilaria tikva-hiae, a dichotomously branched species, displays awide range of habit morphologies ranging from thinto thick, entirely flat to terete phenotypes. Morpho-logically different specimens of G. tikvahiae are oftenfound growing on the same rock. Branching patternin G. damaecornis is still more constant even amongspecimens from distinct geographic regions, and thedegree of thallus compression also vary greatly.Gracilaria lacinulata shows a broad range in bladewidth and branching pattern but is characterized by adistinctly flattened green thallus.

Previous rbcL analysis (unpublished data) revealedthat the green Gracilaria sp. variety farmed at HarborBranch Oceanographic Institute is part of this Gracilar-ia subgroup. This taxon corresponds to an unidentifiedspecies originally collected on the eastern U.S. coastthat has never been found in the field again. All three


Harbor Branch Oceanographic Institution Gracilariavarieties (brown, green, and red) have been kept inculture since 1977, 1982 and 1982, respectively, (D.Hanisak, HBOI, personal communication) and do notdevelop reproductive structures in the cultures. Thebrown variety is a true G. tikvahiae and part of subgroupVIII, but the red variety, producing the highest qualityagar, is part of subgroup IV (unpublished data). TherbcL DNA sequence analysis of the three Gracilariavarieties mentioned above have also been depositedin GenBank (brown5AY049362, red5AY049310,green5AY049311).

Subgroup IX—the G. bursa-pastoris clade: Deepernodes within Gracilaria subgroup IX, composed ofthe 15 most derived species, have low bootstrapsupport in the MP (Fig. 1) analysis and even less in theME trees (data not shown). In the Bayesian tree thesenodes have higher support, with the exception of G.spinulosa and Gracilaria sp. from the Philippines. Inthis subgroup, four distinct clades are resolved withhigh support. Two of these clades are composed of flatand compressed species from the western Atlantic: G.occidentalis, G. ornata, and Plocaria flabelliforme, P. et H.Crouan in Schramm & Maze (1865, p. 21) with 100/84/85% support (Bayesian/MP/ME, respectively) andG. apiculata, G. cervicornis, G. domingensis with 100/97/97% support (Bayesian/MP/ME, respectively). Thephylogenetic position of G. curtissiae in the latter cladehad 100% Bayesian support but was not resolv-ed in either MP or ME analyses (no BP support).The third clade is composed of the eastern Atlanticspecies G. bursa-pastoris and G. multipartita with 100/98/96% support (Bayesian/MP/ME, respectively). Thefourth and most derived clade is the least supportedcluster (64% Bayesian support and no BP support forneither MP nor ME) composed of the remaining sixspecies in this subgroup, all with an east South Africanand Indo-Pacific distribution.

Thirteen of the fifteen species in subgroup IX haveboth a foliose habit and textorii-type spermatangial con-ceptacles. The exceptions are the compressed speciesG. bursa-pastoris and G. cervicornis; and G. domingensisbearing verrucosa-type spermatangial conceptacles.This lineage is composed of well-known species of Gra-cilaria and one unidentified species from the Philip-pines that is morphologically similar to, but geneticallydistinct from, G. textorii.

The most derived lineage in subgroup IX holds thetype of the South African endemic genus Tyleiophora J.Agardh, G. beckeri ( J. Agardh) Papenfuss. This species issister to another South African-Madagascar endemic(Silva et al. 1996), G. capensis. Jacob Agardh (1890)established the genus Tyleiophora to contain Gracilariaspecies with tetrasporangia aggregated in nemathecia.Dawson (1949) reported that a tetrasporangial nemathe-cium is not a stable character and demonstrated thatmany flat northeastern Pacific species display a variabledegree of nemathecal development. Papenfuss (1952)subsequently concluded that this character should notbe used to recognize genera, merging Tyleiophora back

into Gracilaria. Gracilaria spinulosa, Gracilaria sp. fromthe Philippines, and G. textorii received low bootstrapsupport (Figs. 1 and 2A), and their phylogeneticrelationship within subgroup IX is still unresolved.

Three frequently confused and morphologicallysimilar species, G. cervicornis, G. domingensis, and G.ferox J. Agardh (1852), were reassessed by Oliveiraet al. (1983). They concluded based on morphologicalgrounds that G. cervicornis and G. ferox are conspecificand that G. domingensis can only be reliably distin-guished from G. cervicornis based on spermatangialfeatures. The molecular study herein confirms that G.cervicornis is a distinct sister taxon to what is known asG. domingensis from Brazil. Specimens of Gracilariarecently collected from Venezuela and Mexico, resem-bling atypical phenotypes of G. cervicornis, turned out tobelong to a distinct species, herein identified as G.apiculata P. et H. Crouan in Schramm and Maze (1865,p. 19) based on examination and comparison ofphotographs of type material housed in BM! andPC!. Another resurrected name, previously recognizedin Kapraun (1993), is based on Plocaria flabelliforme. Anew combination is made in this study for this com-mon, flat, western Atlantic tropical Gracilaria species.Several specimens of G. apiculata and G. flabelliformewere sequenced (data not shown); these taxa representcommon species for the Caribbean and the southernGulf of Mexico passing under the names G. cervicornisand G. mammillaris, respectively.

Male reproductive structures. Dawson (1949) was thefirst to stress the importance of the shape and originof spermatangial conceptacles in the taxonomy of theGracilariaceae. Ohmi (1958) pointed out that theywere the most important character to distinguishamong species. Yamamoto (1975, 1978) divided thegenus Gracilaria sensu lato (including Gracilariopsis)into three subgenera based on three different types ofspermatangial conceptacles previously recognized byThuret and Bornet (1878) and Dawson (1949, 1961):a subgenus Gracilariella (spermatangia flush withsurface: chorda type, as in Gracilaria chorda [Holmes]Ohmi [1958, p. 50]), Textoriella (spermatangia orga-nized in shallow pits: textorii type, as in G. textorii,Fig. 2B), and Gracilaria (spermatangia organized indeep pits: verrucosa type as in Gracilaria verrucosa5G. gracilis, Steentoft et al. 1995, Fig. 2C). Later,Yamamoto (1984) included other kinds of sperma-tangial types in his classification, such as the symmetricatype and the henriquesiana type (Bird 1995), for whichhe did not established any new subgenera.

Tseng and Xia (1999) formally described the newsubgenus Hydropuntia to include species with sperma-tangial conceptacles in multiple cavities (Fig. 2F) inwhich the spermatangia cover the entire surface of theconceptacles (encompassing the Polycavernosa andhenriquesiana types). The superficial spermatangia ofthe chorda type have been considered ancestral with thedeeper and complex conceptacles considered derived(Yamamoto 1975, 1978, 1984, Tseng and Xia 1999).Yamamoto (1984) presented a schematic diagram


depicting a sequence that had the chorda-type config-uration giving rise to the other more complex types:chorda type (type 1, spermatangia continuously andhomogeneously distributed along the thallus surface),to the symmetrica type (type 2, spermatangia superficialbut discontinued by large scattered cortical cells), to thetextorii type (type 3, shallow cavity, Fig. 2B), to theverrucosa type (type 4, deep cup-shaped cavity, Fig. 2C),to the henriquesina type (type 5, aggregation ofverrucosa-type conceptacles), and finally to the Poly-cavernosa type (5Hydropuntia type, Fig. 2F) with deepconfluent and branched conceptacles.

The chorda type is now known to be characteristic ofand restricted to the genus Gracilariopsis. With theexception of Melanthalia for which there is still noreported spermatangial description, the two majorbasal lineages in the rbcL tree (i.e. Gracilariopsis andCurdiea) have superficial spermatangia with small color-less spermatia and do not form conceptacles (Fredericqand Hommersand 1989b, 1990b, Nelson and Knight1997). Male structures in Gracilariopsis differ from thoseof Curdiea in having the spermatangium cut off singly bytransverse division of the spermatangial parent cell andby not having spermatangia organized in nemathecia.The ancestral condition for the Gracilariales appears tobe one in which undifferentiated cortical cells producedspermatangia by oblique longitudinal divisions, follow-ing the same division pattern as the surface cells.

Our results agree with Yamamoto (1984) andBellorin et al. (2002) in which the most plesiomorphicspermatangial state in the Gracilariaceae seems to bethe chorda type. However, this study does not supportthe phylogenesis hypothesis provided by Yamamoto(1984). In light of the new molecular evidenceproduced in this study, the evolutionary history ofspermatangial types in the Gracilariaceae is morevariable and complex than currently appreciated.Based on literature accounts for the species includedin this study, the Hydropuntia type of spermatangialconceptacle (hereafter treated as synonymous to thehenriquesiana and the Polycavernosa type) is present infour Gracilaria subgroups: in all taxa placed in sub-group II (G. edulis, Abbott et al. 1991) and subgroupIII (G. caudata, Plastino and Oliveira 1997; G. crassi-ssima, Fredericq and Norris 1985), in G. domingensisfrom subgroup IX (Guimaraes et al. 1999), and inG. damaecornis (Ganesan 1989) from subgroup VIII.However, the independent acquisition of the Hydro-puntia type by G. damaecornis and G. domingensismay notcorrespond to a true homoplasy but to misidentifica-tions. It is possible that more than one species maybe passing under the names G. damaecornis and G.domingensis and that these taxa may indeed correspondto two distinct species complexes in need of a carefulsystematical revision.

This study reveals that a ‘‘chilensis’’ type of sperma-tangial conceptacle is possibly the ancestral sperma-tangial configuration within Gracilaria sensu lato. Thetextorii type, considered the most primitive, is in factpresent in the most derived lineages (subgroup IX).

These results suggest that the textorii type as currentlydefined arose independently at least twice in Gracilariasensu lato, once in the G. chilensis lineage (proposed hereas the chilensis type) (Table 3, Fig. 2I), and once in themost derived subgroups characterized by G. bursa-pastoris, G. cervicornis, and G. textorii (proposed here asthe true textorii type) (Table 3, Fig. 2B).

There are reports that the verrucosa and Hydropuntiatype of spermatangia have been found on the samethallus in several Indo-Pacific (Abbott et al. 1991) andAtlantic (Ganesan 1989, Plastino and Oliveira 1997)species and that both the textorii and verrucosa type ofspermatangial conceptacles have been reported fromthe same thallus in ‘‘G. blodgettii’’ Harvey (Zhang andXia 1985, Reading and Schneider 1986, Abbott 1988).Those reports suggest that the verrucosa-type concep-tacle may develop into a Hydropuntia type when inter-calary spermatangial parent cells fuse back to vegetativecells (see fig. 14 in Fredericq and Hommersand 1990bfor H. crassissima) or that a textorii type may develop intoa verrucosa type if the conceptacle deepens into thethallus. However, our observations do not point in thisdirection. So far, only subgroups IVand V seem to havespermatangia restricted to the verrucosa type, which aremorphologically distinct from the verrucosa type re-ported for species placed in other subgroups in ourrbcL phylogenies. Comparisons between verrucosa typeof spermatangia between species from subgroups IVand V with those found on species from subgroups IIand III reveal a remarkable distinction. The sperma-tangial parent cells from species from subgroups IVandV never interact with medullary cells, and the verrucosatype of spermatangia in these species never developinto the Hydropuntia type. On the other hand, sperma-tangial parent cells from species from subgroups II andIII always interact (via secondary pit-connections) withmedullary cells, and it is on these groups that reports ofplants carrying both kinds of spermatangial concepta-cles have been made (Abbott et al. 1991). Therefore,the way the spermatangial parent cells interact withvegetative cells is the key character to distinguish thesetwo groups of Gracilaria sensu lato species and helps torecognize Hydropuntia as a distinct, stable, and reliablegenus from Gracilaria sensu stricto. In species ofGracilaria sensu stricto with the true verrucosa type ofspermatangia (the one that does not interact withmedullary cells) (Fig. 2C), as the thallus age the corticalcells multiply after the spermatangial conceptaclegrowth. This development pattern is very evident inmature spermatangia fromG. salicornia (Abbott 2000, p.215) and G. shimodensis (Tereada and Yamamoto 2000,p. 192), species characterized by having only verrucosatype of spermatangial conceptacles that do not everdevelop into the Hydropuntia type.

The observation of more than one kind of sperma-tangial conceptacle for a particular Gracilaria species,especially when the textorii type and the verrucosa typeare said to co-occur on the same species, should beconsidered with caution because more than one speciesmay have been considered in those studies. Also, the


possibility of hybridization between two distinct taxashould be considered. Hybridization tests in vitro havebeen applied to infer limits among species of Gracilaria(Bird and McLachlan 1982, Plastino and Oliveira 1988),but nothing is known about how this corresponds in situ.

The integration of newly generated rbcL phyloge-nies (Figs. 1 and 2A) and new morphological inter-pretations of male reproductive structures support theseparation of Gracilaria sensu lato into four distinctgroups based on kind of spermatangial conceptacle:the chilensis type (Fig. 2I), composed of only Gracilariasubgroup I; the Hydropuntia type (Fig. 2F), composedof subgroups II and III; the verrucosa type (Fig. 2C),composed of subgroups IV and V; and the textorii type(Fig. 2B), composed of the most derived subgroupsVI–IX. A more detailed comparative analysis ofspermatangial ontogeny and anatomy among thesefour groups may reveal news insights about how tointerpret them in a taxonomically and evolutionaryframework. Ontogenetic observations show that thedegree of interactions between spermatangial mothercells with cortical or medullary vegetative cells is a moreimportant morphological character than the shape ofmature conceptacles (Fredericq and Norris 1985).

Female reproductive structures. The rbcL phylogeniespresented in this study (Figs. 1 and 2A) corroborateFredericq and Hommersand’s (1990b) synthesis ofcystocarp types for the family Gracilariaceae. Theseauthors recognized four distinct cystocarps for thenonparasitic genera:

1. The Curdiea/Melanthalia type: Cystocarp cavitycompletely filled by gonimoblasts, multinucleatedtubular cells absent, carposporangia formed in distinct,elongate, narrow files of similarly sized cells, gameto-phytic cells in the floor of cystocarp becomingcytologically transformed, incorporation of gameto-phytic vegetative cells into the fusion cell restricted tocells of the sterile filaments of the supporting cell.

2. The Gracilariopsis type: Cystocarp cavity notcompletely filled by gonimoblasts; multinucleated tub-ular cells absent; carposporangia aligned in compara-tively straight chains with smaller immature carpospor-angia at the base and larger mature carposporangiaat distal portion of chains; gametophytic cells in floorof cystocarp cytologically transformed, incorporationof gametophytic vegetative cells into the fusion cellrestricted to cells of the sterile filaments of the support-ing cell.

3. The Hydropuntia type: Cystocarp cavity notcompletely filled by gonimoblasts, multinucleated basaland lateral tubular cells often present, multinucleatedupper tubular cells often absent, carposporangia oftenaligned in straight chains with sharp transition betweengonimoblast mass and a mature narrow carpospor-angial layer, cytologically transformed gametophyticcells in floor of the cystocarp often present andcomposed of small cells arranged in layers, incorpora-tion of gametophytic vegetative cells into the fusion cellnot restricted to sterile filaments of the supporting cell,

fusion cell becomes highly reticulate and inconspic-uous, gonimoblast mass with regular development,gonimoblasts with variable cell wall thickness (Fig. 2G).

4. The Gracilaria type: Cystocarp cavity not com-pletely filled by gonimoblasts, multinucleated basal andupper tubular cells often present, carposporangiaorganized in clusters of cells of variable sizes, gameto-phytic cells in floor of cystocarp not transformed cytolo-gically, incorporation of gametophytic vegetative cellsinto the fusion cell not restricted to sterile filaments ofthe supporting cell, mature fusion cell globose, variedlyramified or indistinct from other large gonimoblasts,inner gonimoblasts with conspicuous thick cell walls.

In light of our molecular results, at least four distinctcystocarp types can now be distinguished within thegenus Gracilaria sensu lato alone (Fig. 2, D and E, G andH, and J):

1. The chilensis type. This cystocarp is morphologi-cally similar to the Gracilariopsis type but with a lessdissected organization of the inner gonimoblasts andwith carposporangia in unbranched chains formed bygonimoblasts that gradually transform into largeterminal carposporangia. This cystocarp type (Fig. 2J)is characteristic and so far only found among membersof Gracilaria sensu lato subgroup I. Morphologicalsimilarities and differences between the cystocarpsof G. chilensis and Gp. lemaneiformis have been welldocumented (Bird et al. 1986, Ryan and Nelson 1991).Among Gracilaria sensu lato species, this cystocarp typelacks multinucleated tubular cells connecting outerpericarp and gonimoblasts, has an extensive cystocarpcavity, a regular pattern of gonimoblast development,large external gonimoblast cells, and orderly arrays ofcarposporangia (Fig. 2J).

2. The Hydropuntia type. This cystocarp type ispresent so far only in Indo-Pacific species once placedin Hydropuntia, members of Gracilaria sensu lato sub-group II (Fig. 2A). Distinct features include anirregularly shaped fusion cell enclosed within thepericarp before gonimoblast initiation, with gonimo-blast filaments developing in nearly complete straightfiles with the inner derivatives linking rapidly with oneanother by means of secondary pit-connections, maturemass of gonimoblasts often branched or lobed, carpo-sporangia organized in short chains with sharp transi-tion with gonimoblast mass (Fig. 2H).

3. The crassissima type. This type of cystocarp ischaracteristic of Gracilaria sensu lato subgroup III.Distinct features include gonimoblast filaments devel-oping in complete straight files producing a regular,not lobed, centralized, and broad-based mature goni-moblast mass with carposporangia in usually shortchains (Fig. 2G). Morphological observations fromspecies included in this study agree with those ofAbbott et al. (1991), who noted that gonimoblastorganization in the Caribbean Hydropuntia species(subgroup III) is centralized, whereas that of PacificHydropuntia (subgroup II) species is diffuse. This type


of cystocarp was illustrated by Fredericq and Norris(1985), Fredericq and Hommersand (1990b), andPlastino and Oliveira (1997).

4. The Gracilaria sensu stricto type. This type ofcystocarp is characteristic of the most derived sub-groups within Gracilaria sensu lato (subgroups IV–IX).Its distinctive features include a regularly shaped, oftenpersistent, fusion cell that can be quite conspicuousthroughout gonimoblast development, gonimoblastfilaments developing at regular or irregularly ratesbut often producing a gonimoblast mass composed oflarge cells with conspicuous cell walls, and withcarposporangia organized in dichotomously branchedchains (Fig. 2, D and E). Usually, when the fusion cell ispersistent, the rate of gonimoblast development isirregular, thus producing an irregularly shaped goni-moblast mass composed of variably sized cells (e.g.G. gracilis, G. tikvahiae). Cystocarps with a more regularrate of gonimoblast development typically produce arounded gonimoblast mass composed of large long-itudinally elongated cells with conspicuous cell walls(e.g. G. flabelliforme).

The presence or absence and location of tubularmultinucleated cells connecting the pericarp with thegonimoblasts alone is not a stable taxonomic charactersto define Gracilaria sensu lato subgroups, with theexception of subgroup I that completely lacks thesecells. However, despite the many homoplasies, apattern can be observed where subgroups II and IIIare often characterized by having them restricted to thebase of the cystocarp cavity, whereas the most derivedsubgroups (IV–IX) are often characterized by typicalGracilaria sensu stricto cystocarps with tubular cellsdistributed along the entire cystocarp cavity.

Tetrasporangia in the Gracilariales are cruciatelydivided or decussate. The development of nematheciaobserved in some species (e.g. G. beckeri) was corrobo-rated by this molecular study as being indistinct at thegeneric level (Dawson 1949, Papenfuss 1952).

CONCLUSIONS

Morphological characters found in the Gracilaria-ceae that do not take into account development oftenresemble one another in the mature state and arenoninformative taxonomically, even among distanttaxa (e.g. shape and size of vegetative cells frequentlyoverlap among species). Also, ontogenetic featuresshould be assessed with care because abortive pre-and postfertilization stages are common (Fredericq andHommersand 1990b).

Delineation of new and previously defined subge-neric groups within Gracilaria sensu lato needs to bereassessed and requires the combination of male andfemale reproductive characters coupled with molecularphylogenies inferred from informative genetic mar-kers. Distinct spermatangial conceptacle types withinGracilaria sensu lato are represented by the chilensis type,the Hydropuntia type, the verrucosa type, and the textoriitype. Distinct cystocarps types within Gracilaria sensu

lato are likewise represented by the G. chilensis type, theHydropuntia-G. crassissima types, and the G. bursa-pastoristype. These four kinds of spermatangial and cystocarporganizations plus the phylogenetic relationships in-ferred from rbcL sequence analyses produced in thisstudy define stable clades at the generic rank. Also inthe literature there is already a plethora of genetic(Bird et al. 1992, 1994, Bird 1995, Bellorin et al. 2002)and morphological (Nelson and Ryan 1991, Ryan andNelson 1991) evidence supporting the uniqueness ofthe subgroup I and its recognition as a distinct genuswithin the Gracilariaceae. The description and delinea-tion of a new genus to accommodate the G. chilensisclade will be done elsewhere. The genus Hydropuntia,defined by the generitype G. urvillei, is herein rein-stated encompassing species from subgroups II andIII. The remaining terminal taxa (subgroups IV–IX)are defined by the generitype G. bursa-pastoris andconsidered the true genus Gracilaria sensu stricto.

At the species level, distinct evolutionary lineageswithin the Gracilaria sensu lato clade (5 subgroups)present strong biogeography patterns of distribution.Subgroups I, II, and IV have to date a restricted Indo-Pacific distribution, whereas subgroups III, VI, VII,and VIII have a western Atlantic restricted distribu-tion. In subgroup IX, the most recent clade in theGracilaria sensu lato phylogeny, certain lineages arerestricted to the western Atlantic (e.g. the G. ornata andthe G. cervicornis lineages), whereas others have a Indo-Pacific-South African distribution (e.g. G. capensis line-age). These patterns suggest that ecological radiationand local speciation are a common phenomenon in thegenus Gracilaria sensu lato. On the other hand, thebiogeography patterns observed in the genus Gracilar-iopsis are different from the ones found in Gracilaria(Gurgel et al. 2003b). Curdiea and Melanthalia clademay present interesting biogeographic patterns, butmore data are needed before they can emerge.

The rbcL genetic distances among the four distinctGracilaria sensu lato generic groups mentioned aboveare consistent with the generic rank differences foundamong accepted Gracilariaceae genera. Placing morethan 100 species within a single genus underestimatesour capacity to recognize different evolutionary his-tories among genetically distinct lineages of Gracilar-iaceae. However, when morphological characters,informative molecular data, and sound phylogenetichypotheses are combined, the recognition of threedistinct genera currently placed within Gracilaria sensulato corresponds to a more natural, phylogeneticallyinformative, and information-rich taxonomy than theone currently in use.

Our results suggest that several independent dis-persal events took place in Gracilaria, Gracilariopsis, andHydropuntia but not in Curdiea and Melanthalia. In thisstudy, the first divergent node in all three Gracilar-iaceae major clades are typically Indo-Pacific indistribution, lending support to the biogeographichypothesis that the order’s ancestor originated ineastern Gondwana before the opening of the Tethyan


Ocean (Hommersand 1990). The austral Tethyangroup is composed of Melanthalia and Curdiea withextant taxa currently found in South Australia,Tasmania, New Zealand, South Africa, and the Antarc-tic Peninsula. Representatives of Gracilaria, Gracilar-iopsis, and Hydropuntia are present in both the Southernand Northern hemispheres, ranging from temperateto tropical environments. Hommersand (1990) sug-gested three major dispersal scenarios: 1) Gracilariopsisand some taxonomic sections of Gracilaria weredistributed from the northwest Pacific to NorthAmerica by way of the Alaskan Peninsula, either in lateCretaceous or in the Paleocene, ultimately reaching theCaribbean Sea, and possibly also Europe and theMediterranean Sea; 2) species clusters in Gracilaria mayhave a Tethyan distribution; and 3) others appear tohave extended their range westward from the IndianOcean to the western Atlantic and Caribbean Sea byway of South Africa. The inclusion in the rbcL data setof more species worldwide is needed to fully assess suchscenarios of ancient dispersal patterns. SSU rDNA dataalso places a Curdiea and Melanthalia clades at the rootof Gracilariaceae trees (Bellorin et al. 2002).

The three major clades of Gracilariaceae may havediverged early in the evolution of the family. The lowbootstrap support for nodes determining the relation-ships among these three clades and of the Gracilariasensu lato subgroups in the MP analysis may beinterpreted as the lack of sufficient phylogenetic signalin rbcL to resolve these relationships (genetic conserva-tion) or a high level of mutation accumulation anda faster rate of gene evolution (gene saturation). Thelatter hypothesis is more likely due to detectedsaturation at the third codon position. Similar lowbootstrap results for particular clades are indicative ofadaptive radiation, lineage sorting, or of a fast originfor major evolutionary clades that originated within ashort period of time from one another, as has beensuggested for other organisms (Mardulyn and Whit-field 1999, Hampl et al. 2001). Phylogenetic analysis ofother red algal families and orders based on differentgenetic markers often present similar bootstrap resultssupporting the latter interpretation (Saunders andKraft 1996, Freshwater and Bailey 1998, Freshwateret al. 1999). The Bayesian analysis has a maximumlikelihood correction for heterogeneity in the mutationrates and provided high probability support for thesame nodes generated by MP.

The inclusion of more Gracilaria taxa in the data setmay better resolve the evolutionary relationships of theclades already observed, especially those with lowbootstrap support. Nevertheless, the rbcL gene showedsigns of significant saturation at the third codonposition, suggesting that another nonsaturated geneticmarker should be used to confirm the phylogeneticrelationships among deeper nodes in the Gracilaria-ceae. As important as sequencing distinct species orusing the proper genetic marker is sequencing multiplespecimens belonging to a same species. By doing so, thefull range of the phenotypic plasticity for a particular

species can be assessed, different forms and varietiesattributed to a particular species confirmed, trans-ferred to another species or recognized as a distincttaxon, and the true taxonomy for certain speciescomplexes, cryptic species, and superspecies evaluated.

NEW COMBINATIONS

Gracilaria flabelliforme (P. et H. Crouan inSchramm et Maze) Fredericq et Gurgel comb. nov.

Basionym: Plocaria flabelliforme P. et H. Crouan inSchramm et Maze 1865, Essai Class.Alg. Guadeloupe,p. 21, #131

Homonym: Plocaria flabelliforme P. et H. Crouan inSchramm et Maze 1866, p. 48

Lectotype: BM!, largest specimen on sheet, AlgaeGuadeloupensis, H. Maze, Purchased 1890, in theGracilaria foliifera folder, 57th 1st series, Monle VieuxBourg.

Type locality: Guadeloupe, collected on submergedrocks in April.

The clade composed ofGracilaria sensu lato subgroupsII and III (Figs. 1 and 2A) is herein recognized andconfirmed as the genus Hydropuntia, distinct from theremaining Gracilaria species. Some of the species namesthat are part of this clade were previously placed inHydropuntia before; thus, the remaining and followingones are transferred to Hydropuntia for the first time:

Hydropuntia caudata ( J. Agardh) Gurgel et Freder-icq comb. nov.

Basionym: Gracilaria caudata J. Agardh 1852, Sp. Gen.et Ordines Alg., 2(2), p. 598

Taxonomic synonyms: See Plastino and Oliveira (1997,p. 229).

Hydropuntia edulis (Gmelin) Gurgel et Fredericqcomb. nov.

Basionym: Fucus edulis Gmelin, 1768. Hist. Fuc., p.133.

Synonyms: Polycavernosa fastigiata Chang et Xia,1963, p. 15, p. 120, pl. I: figs. 1–12, pl. II: figs. 1–6;Gracilaria edulis (Gmelin) Silva, 1952, p. 293; Hydro-puntia fastigiata (Chang & Xia) Wynne, 1989, p. 477;Sphaerococcus lichenoides C. Agardh 1822, p. 310;Sphaerococcus lichenoides var. tenuis C. Agardh 1824,p. 234.

Taxonomic synonyms: See Silva et al. (1996, p. 175).Hydropuntia eucheumatoides (Harvey) Gurgel et

Fredericq comb. nov.Basionym: Gracilaria eucheumoides Harvey, 1860,

Proceedings Amer. Acad. Arts Sci. 4:331 (as ‘‘eucheu-mioides’’).

Taxonomic synonyms: See Silva et al. (1996, p. 168)as Gracilaria eucheumatoides Harvey.

Hydropuntia preissiana (Sonder) Gurgel et Freder-icq comb. nov.

Basionym: Rhodymenia preissiana Sonder, 1845, Bo-tanische Zeitung 3, p. 56 (as ‘‘Rhodomenia’’)

Synonyms: Rhodophyllis preissiana (Sonder) Kutzing,1849, pp. 786–7; Calliblepharis preissiana (Sonder)Harvey, 1859, pl. cvi.; Gracilaria preissiana (Sonder)


Womersley in Min-Thein et Womersley, 1976, p. 109;Withell, Millar et Kraft, 1994, pp. 294–7, figs. 11–13.

Taxonomic synonyms: See Silva et al. (1996, p. 174).Hydropuntia rangiferina (Kutzing) Gurgel et Fre-

dericq comb. nov.Basionym: Sphaerococcus rangiferinus Kutzing, 1849,

Sp. Alg., p. 779 (5 Sphaerococcus cervicornis Kutzing,1843, Phyc. Gen. Pl. 62, fig. II; see Abbott et al. 1991)

Synonyms: Gracilaria dentata J. Agardh 1852, p. 603;Polycavernosa dentata (J. Agardh) Lawson & John 1982,p. 228; Hydropuntia dentata (J. Agardh) Wynne 1989, p.477; Gracilaria henriquesiana Hariot 1908, p. 162; Poly-cavernosa henriquesiana (Hariot) Chang et Xia 1968, pl.2, fig. 6; Hydropuntia henriquesiana (Chang et Xia)Wynne 1989, p. 477.

Hydropuntia secunda (P. et H. Crouan) Gurgel etFredericq comb. nov.

Basionym: Gracilaria secunda P. et H. Crouan inSchramm et Maze 1865, Essai Class. Alg. Guade-loupe, p. 19. Not Gracilaria secunda (Ag.) Zanardini1840: Biblioth. Ital. (Milano) 99, p. 214 [Sphaerococcussecundus Ag.]

Hydropuntia usneoides (C. Agardh) Gurgel et Fre-dericq comb. nov.

Basionym: Sphaerococcus usneoides C. Ag. 1822, Sp.Alg., p. 333.

Synonym: Gracilaria usneoides (C. Ag.) J. Agardh1852, Sp. Alg., 2(2), p. 595.

This work was submitted as part of the Ph.D. dissertation byC. F. D. Gurgel to the Department of Biology, University ofLouisiana at Lafayette. This study was supported in part by aSmithsonian Institution and Link Foundation GraduateSummer Internship at the Smithsonian Marine Station at FortPierce, Florida; a Sigma Xi Graduate Research Grant-in-Aid,Phycological Society of America Grant-in-Aid for research andHoshaw Travel Awards and UL Lafayette GSO financial awards(1997–2000) to C. F. G., and a U.S. Department of Energygrant DE FG02-97ER122220, NURC-NOAA grant NA96RU-0260, and NSF grant DEB-9903900 to S. F. The collectorsK. S. Cole, J. Cabioch, W. Freshwater, S. M. Lin, A. Millar, W.Nelson, A. Renoux, J. N. Norris, H. B. S. Womersley, B. Wysor,M. Yoshizaki, A. Taouil, and especially L. M. Liao and Max H.Hommersand sent multiple vouchers and are greatly acknowl-edged. We thank Paul C. Silva and Jim N. Norris for their helpwith nomenclature, Naomi Phillips for help with MrBayes, andJuan Lopez-Bautista, Gary Saunders, and the two anonymousreviewers for their constructive comments on the manuscript.

We would also like to thank J. Rueness, W. Nelson, and D.Hanisak for their personal communications. This studyrepresents Smithsonian Marine Station at Fort Pierce contribu-tion no. 571.

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SYSTEMATICS OF THE GRACILARIACEAE (GRACILARIALES ... · of a two-celled carpogonium branch, 2) a supporting cell producing other two to three two-celled sterile ﬁlaments, 3) the

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