University of Iowa Iowa Research Online eses and Dissertations Spring 2010 Evolution Of shape morphologic variation of the genus Undaria (Scleractinia, Agariciidae) Kristopher J S Rhodes University of Iowa Copyright 2010 Kristopher J S Rhodes is thesis is available at Iowa Research Online: hps://ir.uiowa.edu/etd/586 Follow this and additional works at: hps://ir.uiowa.edu/etd Part of the Geology Commons Recommended Citation Rhodes, Kristopher J S. "Evolution Of shape morphologic variation of the genus Undaria (Scleractinia, Agariciidae)." MS (Master of Science) thesis, University of Iowa, 2010. hps://doi.org/10.17077/etd.iluilxla
53
Embed
Evolution Of shape morphologic variation of the genus Undaria
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
University of IowaIowa Research Online
Theses and Dissertations
Spring 2010
Evolution Of shape morphologic variation of thegenus Undaria (Scleractinia, Agariciidae)Kristopher J S RhodesUniversity of Iowa
Copyright 2010 Kristopher J S Rhodes
This thesis is available at Iowa Research Online: https://ir.uiowa.edu/etd/586
Follow this and additional works at: https://ir.uiowa.edu/etd
Part of the Geology Commons
Recommended CitationRhodes, Kristopher J S. "Evolution Of shape morphologic variation of the genus Undaria (Scleractinia, Agariciidae)." MS (Master ofScience) thesis, University of Iowa, 2010.https://doi.org/10.17077/etd.iluilxla
A thesis submitted in partial fulfillment of the requirements for the Master of Science degree in Geosciences in the Graduate College of The University of Iowa
May 2010
Thesis Supervisor: Professor Ann F. Budd
Graduate College
The University of Iowa
Iowa City, Iowa
CERTIFICATE OF APPROVAL
____________________________
MASTER’S THESIS
_________________
This is to certify that the Master’s thesis of
Kristopher J S Rhodes
has been approved by the Examining Committee for the thesis requirement for the Master
of Science degree in Geoscience at the May 2010 graduation.
Thesis Committee: Ann Budd, Thesis Supervisor Hallie Sims Gene Hunt
ii
To AJ
iii
ACKNOWLEDGMENTS
Thanks to the University of Iowa Dept. of Geoscience for funding, as well as Nancy
Budd, Hallie Sims, Gene Hunt, Jim Klaus, Don McNeill, Tiffany Adrain and the SUI
Paleontology Repository, and Tom Stemann. Much gratitude is also due to Abby
Michaelson, and all of my fellow graduate students, for providing insight, encouragement
and all others kinds of necessary assistance.
iv
TABLE OF CONTENTS
LIST OF TABLES -------------------------------------------------------------------------- v
LIST OF FIGURES ------------------------------------------------------------------------- vi
CHAPTER I INTRODUCTION AND BACKGROUND ------------------------ 1
Coral morphology and plasticity --------------------------------------------------------------- 1
The family Agariciidae and the genus Undaria ----------------------------------------------- 3
Change through time: Stasis and gradualism ------------------------------------------------- 4
Previous Work ------------------------------------------------------------------------------------ 6
Location and Geologic Setting ----------------------------------------------------------------- 6
Table 1 Specimens used 18 Table 2 Landmarks used for this project. 21 Table 3 CVA cross validation results. 29 Table 4 Aikiele information criteria for three models of evolution for shape and size
variables. 37
vi
LIST OF FIGURES
Figure 1 Geologic setting and locality data. 9 Figure 2 Interpreted local sea level and time for Cibao valley deposition. 10 Figure 3 Landmark diagram. 22 Figure 4 Growth vectors associated with width by species 23 Figure 5 Deformation along the first principal component. 30 Figure 6 Deformation along the second principal component. 31 Figure 7 Deformation along the third principal component. 32 Figure 8 Deformation along the fourth principal component. 33 Figure 9 Time series of shape and size variables by species. 34 Figure 10 Regression of Undaria crassa shape vs. environmental variables. 38
1
CHAPTER I INTRODUCTION AND BACKGROUND
Great advances have been made in understanding the patterns of morphologic
change observed in the fossil record in the past 40 years. Starting with Eldredge and Gould’s
(1972) punctuated equilibrium, a number of increasingly appropriate and informative models
have been used to explain patterns of stasis and change in the fossil record (Bookstein 1987,
Roopnarine, Byars, and Fitzgerald 1999, Hunt 2006, Estes and Arnold 2007). It has
increasingly been recognized that different patterns are active over geologic time including
random walks, directional change, and stasis. What must now be focused on is applying
these methods across disparate taxa, in the hopes of understanding when these disparate
modes of evolution are active and what controls them.
Scleractinian corals are an important group today, serving literally as the framework
for reefs worldwide. These reefs provide habitat for a complex ecosystem with great value of
mankind, serving as a source of food, protection, and recreation. However, these reefs are
under threat today (Hoegh-Guldberg et al. 2007, Carpentor et al. 2008). While it is clear that
environmental stresses are wreaking havoc on coral populations in the short term, it is less
clear how corals will respond to a changing environment over geologic time. The genus
Undaria (Scleractinia: Agariciidae) is a common fossil coral in the Neogene of the Caribbean.
This study will focus on three species of Undaria from the Yaque group of the Dominican
Republic, to understand how shape at the corallite level has changed through time.
Coral morphology and plasticity
Most scleractinian corals are colonial animals that, in adult form, produce skeletal
hard parts by depositing layers of aragonite, with growth of structure controlled by
1 The point where the septum along the outer left corallite margin intercepts the outer
corallite ridge.
2 Following the ridge from the top left of the corallite, where the first major septum to
where it intersects with the corallite floor (the base).
3 Top of corallum.
4 As #2, mirrored to the inner side of the coralite.
5 The point where the septum along the inner left corallite margin intercepts the inner
corallite ridge.
6 The intersection of the septa along the outer left corallite margin and a septum that
reaches the corallite’s center.
7 As #6, mirrored to the outer edge of the corallite.
8 From point #6, move to the first major septa counterclockwise from it, at its base. If
the same septum creates the intersections responsible for both points 6 and 7, use
that septum.
9 The point where the septum from #8 meets the wall between corallites.
10 The point of greatest curvature along the septum indicated in #2. This approximates
the end of the line of organic deposition described in Stolarski (2003).
11 The intersection of the septum from #10 and the outer corallite ridge.
12 The point of greatest curvature along the septum indicated in #4. This point is the
mirror of #10 across the axis of the ridges.
13 As #11, except on the corresponding septum on the inner side of the corallite.
22
Figure 3 – Landmark diagram. Also, see table 2. Image based on Stemann (1991).
23
Figure 4- Growth vectors associated with width by species.
4.1- Undaria crassa. Model is regression of shape variables against width. Percent of variance
explained is 17.1%. Regression was significant by permutation test, p <0.001. Black outline is
the mean form, while blue lines show vectors of shape change associated with larger size.
24
Figure 4 continued.
4.2- Undaria agaricites. Model is regression of shape variables against width. Percent of
variance explained is 15.2%. Regression was significant by permutation test, p <0.001. Black
outline is the mean form, while blue lines show vectors of shape change associated with
larger size.
25
Figure 4 continued.
4.3-Undaria sp. A. Model is regression of shape variables against width. Percent of variance
explained is 18.8%. Regression was significant by permutation test, p <0.001. Black outline is
the mean form, while blue lines show vectors of shape change associated with larger size.
26
CHAPTER III RESULTS
Canonical variates analysis
For the combined Gurabo and Mao formations, 189 of 195 (96.9%) individuals were
correctly identified. Cross validation of this data set resulted in 184 of 195 (94.4%)
individuals correctly identified (Table 3.1). All of the observed misidentifications were
between U. agaricites and U. crassa.
For the individuals from the Cercado formation, 83 of 86 (96.5%) were correctly
identified. Cross validation of this data set resulted in 64 of 86 (74.4%) correctly identified
(Table 3.2). All individual corallites that were misassigned by this CVA had other corallites
from the same colony correctly assigned. All specimens with incorrect assignments from this
set were reexamined according to the criteria of Stemann (1991). While corallite morphology
between these two species are quite similar, especially from the Cercado formation,
traditional criteria such as corallite size and row length allow a consistent differentiation of
species, and no individuals were reassigned. Once again, all of the observed
misidentifications were between U. agaricites and U. crassa.
Principal components analysis
The first four principal components were statistically significant. The first principal
component explained 28.74% of the variance. Higher values of the value of the first
principal component are primarily associated with lower ridges and shallower calice (figure
5). U. crassa tended to have lower average values on PC1, and U. sp. A tended towards higher
values. The first principal component seems to correspond to the differing growth forms of
Helmuth and Sebens (1993), with higher scores on this axis relating to the upright/bifacial
growth form.
27
The second principal component explained 16.95% of the variance. Higher values on
this principal component are related to a shift in the central pit towards the colony center
relative to the ridges, as well a change in the geometry of landmarks 6 and 7 along the
corallite edge (figure 6).
The third principal component explains 11.47% of the variance. Higher scores on
this component are associated with higher walls separating the corallites in a single meander
(figure 7).Undaria sp. A tended had a lower mean value on this trait then the other two
species, which tracked each other through time. The fourth principal component explains
6.96% of the observed variance, and primarily describes a change in the distance of
landmarks 6 and 7 from the corallite center, with landmark 6 moving away from and 7
moving towards the center with increased values of this principal component (figure 8).
In U. crassa, the student’s t test revealed a significant change between the Gurabo and
Cercado formations for PC1 and PC3 (p = 0.044 and p < .0001, respectively). For U.
agaricites, there was a significant difference in mean of PC1 between the Gurabo and Cercado
formations (p = .007). For U. sp. A, there was a significant shift in PC1 between the Mao
and Gurabo formation (p = .013).
Evolutionary model fits
AICc values by model and species for each significant principal component and
centroid size are listed in table 4. Across the first four principal components, the stasis
model was preferred 8 times while the unbiased random walk (URW) model was favored 4
times. In those cases where the URW model was preferred, the AICc values were always
within two units of the stasis model. For log of centroid size, the preferred model for U.
crassa is stasis, while the preferred models for U. agaricites and U. sp. A is URW.
28
Regression
For U. crassa, the single specimen from the Cercado formation was excluded from
regression and PLS analysis. Deposition rate and SST/SSE were statistically significant
predictors of shape (figure 10), p = 0.010 and 0.044 respectively, while local depth and
upwelling were not significant. Regression against deposition rate resulted in a correlation of
.43, R^2 = 18.4%, while SST/SSE explained 14.3%. The change in shape associated with
these is shown in figure 10. For U. agaricites and U. sp. A, none of the environmental
variables were significant predictors of shape.
Partial least squares
All partial least squares results were not statistically significant (p > 0.05).
29
Table 3- CVA cross validation results. Each row shows how many individuals assigned a
priori to the various species are classified to each species by the CVA procedure. Priors are
the proportion of individuals assigned to each group a priori.
3.1- CVA cross validation results for all specimens from Gurabo and Mao formations. ______________________________________________________________
From sp. U. sp.A U. agaricites U. crassa Total U.sp.A 77 0 0 77 % 100.00 0.00 0.00 U. agaricites 0 67 4 71 % 0.00 94.37 5.63 U. crassa 0 7 40 47 % 0.00 14.89 85.11 Total 77 74 44 195 % 39.49 37.95 22.56 Priors 0.39487 0.3641 0.24103
3.2- CVA cross-validation for all specimens from Cercado formation. __________________________________________ From sp. U. agaricites U. crassa Total U. agaricites 58 12 70 % 82.86 17.14 100.00 U. crassa 10 6 16 % 62.50 37.50 100.00 Total 68 18 86 % 79.07 20.93 100.00 Priors 0.81395 0.18605
30
Figure 5- Deformation along the first principal component. PC1 explained 28.7% of the
variance. Black outline is the average shape, while red outline shows the shapes associated
with a PC score 0.2 higher than mean.
31
Figure 6- Deformation along the second principal component. PC2 explained 16.9% of the
variance. Black outline is the average shape, while red outline shows the shapes associated
with a PC score 0.1 higher than mean.
32
Figure 7- Deformation along the third principal component. PC3 explained 11.5% of the
variance. Black outline is the average shape, while red outline shows the shapes associated
with a PC score 0.1 higher than mean.
33
Figure 8- Deformation along the fourth principal component. PC4 explained 6.9% of the
variance. Black outline is the average shape, while red outline shows the shapes associated
with a PC score 0.1 higher than mean.
34
Figure 9-Time series of shape and size variables by species.
9.1- First principal component through time. Red: Undaria sp. A, Blue: Undaria agaricities,
Black: Undaria crassa. Bars show one standard error, with variance pooled.
9.2- Second principal component through time. Red: Undaria sp. A, Blue: Undaria agaricities,
Black: Undaria crassa. Bars show one standard error, with variance pooled.
35
Figure 9 continued.
9.3- Third principal component through time. Red: Undaria sp. A, Blue: Undaria agaricities,
Black: Undaria crassa. Bars show one standard error, with variance pooled.
9.4- Fourth principal component through time.Red: Undaria sp. A, Blue: Undaria agaricities,
Black: Undaria crassa. Bars show one standard error, with variance pooled.
36
Figure 9 continued.
9.5- Centroid size through time. Red Undaria sp. A, Blue: Undaria agaricities, Black: Undaria
crassa. Bars show one standard error, with variance pooled.
37
Table 4-Akaike information criteria for three models of evolution for shape and size variables. For explanation of models, see methods.
PC1 PC2 PC3 PC4 ln(Centroid size)
DE URW Stasis DE URW Stasis DE URW Stasis DE URW Stasis DE URW Stasis
U. sp. A -5.9 -10.8 -9.2 -12.1 -16.1 -17.8 -13.7 -18.5 -25.9 -21.0 -25.8 -26.6 3.7 -1.3 -0.1
preferred * * * * *
38
Figure 10- Regression of Undaria crassa shape vs. environmental variables.
10.1- Shape change associated with deposition rate. Percent variance explained = 18.4%. P =
0.010 by permutation test. Red outline reflects a deposition rate 0.3mm/year higher then
black reference form.
10.2- Shape change associated with change in sea surface temperature/salinity proxy. Percent
variance explained = 14.1%. P = 0.044 by permutation test. Red outline reflects an increase
of Globigerinoides sacculifer abundance of 50%.
39
CHAPTER IV DISCUSSION
This study shows that stasis is the dominant evolutionary mode for the genus
Undaria through the Neogene of the Cibao Basin, Dominican Republic. The results broadly
agree with Hunt (2007a). He found that for 251 time series of organismal traits, 37% of the
examined size-related traits were best fit by the stasis model, and 60% of shape traits were
best fit by the stasis model. In this study, 1 of 3 (33%) size traits were best fit by the stasis
model, while 8 of 12 (67%) shape traits were best fit by the stasis model. Stasis may be more
pervasive in Undaria than these results suggest; even when preferred by the data, support for
the unbiased random walk model was usually only slightly higher than that for the stasis
model, while the stasis model was often strongly preferred over the others. This could easily
be the result of small sample sizes at some stratigraphic levels and a relatively small number
of stratigraphic levels included.
These results strengthen the conclusions of Stemann (1991), that stasis is the general
mode of evolution for Undaria through this section. In this study, positive evidence for stasis
was discovered, as opposed to finding a lack of change. Additionally, some evidence for
change was found that should be reconciled with the broader pattern of stasis.
The evidence for change through time found here does not mean that the pattern of
stasis is rejected. Stasis models allow for some change through time, and some small changes
have always been within its purview (Eldredge and Gould 1972, Gould 2002). The
microevolutionary and ecologic causes of the observed pattern of stasis are not well
understood (Eldredge et al. 2005). The pattern of stasis has been explained as both a result
of stabilizing selection (Estes and Arnold 2007, Gould 2002) and of ecological interactions
coupled with microevolutionary processes (Lieberman and Dudgeon 1996, Hansen and
Houle 2004). This study does not provide clear support for either of these.
40
Attempts to find potential causal factors of the observed changes were not
particularly successful. While regression showed a correlation between the shape of U. crassa
and two environmental variables, both of these variables were correlated with each other as
well as with time. If similar responses were seen across all the species, it would be possible to
suggest an adaptive response. In this case it seems premature to suggest this.
Additionally, patterns observed in the CVA analysis by formation may be
informative to understanding these changes. Cross validation of corallites from the Cercado
formation (6.5 – 6.0 mya) resulted in 74.4% being correctly identified, while the same
analysis from individuals from the Gurabo formation (5.8 – 4.0 mya) resulted in 94.4% of
corallites correctly identified. This results primarily from a shift in morphospace occupied by
U. crassa, from a location proximal to U. agaricites to a location farther away, most notably on
PC1 and PC3. One explanation for this shift would be a speciation event followed by
divergence into available morphospace. The oldest reported occurrences of these taxa both
occur in the Cercado formation (Budd et al. 2001). This kind of event – a gradual
morphologic divergence between closely related species – has been reported from the Cibao
group in mollusks (Nehm and Geary 1994), but is generally rarely observed (Gould 2002).
This may be an example of an event rarely seen in the fossil record: a nascent divergence that
occurs over a geologically significant time. Further study both on these taxa, and others from
this group, seems warranted.
41
CHAPTER V CONCLUSIONS
In this study, the corallite shapes of three species of the scleractinian genus
Undariafrom the Yague group, Dominican Republic, were examined through a period of
time stretching from 6.4 mya to 3.4 mya, a total of 3.0 ma. Corallite shape was measured
using 3 dimensional landmarks and manipulated using the well established procedures of
geometric morphometrics. Differences in shape and size through time were examined using
a variety of tools, including canonical variates analysis, principal components analysis, least
squares regression, partial least squares regression, and a variety of evolutionary model fits.
Evolutionary model fits were used to test three models against the shape and size variables:
directional evolution, which models a directional change through time; unbiased random
walk, which models random change through time; and stasis, which models stability through
time. In summary:
1. Stasis seems to be the most common pattern through the section, with a
proportion of support for stasis (9 of 15, 60%) and unbiased random walk (6 of
16, 40%) models similar to that observed in other studies for both shape and size
variables. None of the observed time series was best explained by the directional
evolution model. This strengthens the evidence for stasis in Undaria through this
section, as described by Stemann (1991).
2. While two of the examined environmental factors seemed to be related to change
through time in U. crassa, namely deposition rate and sea surface
temperature/salinity, they were correlated to both each other and time. As such, a
single underlying factor – also correlated to time – could explain the observed
pattern. The evidence that these environmental factors were the causal agent of
shape change is weak.
42
3. The first occurrences of U. crassa and U. agaricitesboth occur at the top of this
section. The distance in morphospace between these two species increases
through time, as represented by the results of CVA and PCA. One plausible
explanation for this would be a speciation event followed by divergence into
available morphospace.
43
REFERENCES
Ayre, DJ, BL Willis. 1988. Population structure in the coral Pavona cactus: Clonal genotypes show little phenotypic plasticity. Marine Biology 99: 495-505.
Bell, AB, MP Travis, DM Blouw. 2006. Inferring natural selection in a fossil threespine stickleback. Paleobiology 32(4): 562-77.
Bookstein, FL. 1987. Random Walk and the Existence of Evolutionary Rates. Paleobiology
13(4): 446-64.
Budd, AF., CT Foster, JP Dawson, KG Johnson. 2001. The Neogene marine biota of tropical America (―NMITA‖) database: accounting for biodiversity in paleontology. Journal of Paleontology 75(3): 743-51.
Cairns, SD, BW Hoekesma, J van der Land. 1999. Appendix: List of extant stony corals.
Atoll Research Bulletin 45: 13-46.
Carpenter, KE, M Abrar, G Aeby, RB Aronson, S Banks, A Bruckner, A Chiriboga, J Cortés, JC Delbeek, L DeVantier, GJ Edgar, AJ Edwards, D Fenner, HM Guzmán, BW Hoeksema, G Hodgson, O Johan, WY Licuanan, SR Livingstone, ER Lovell, JA Moore, DO Obura, D Ochavillo, BA Polidoro, WF Precht, MC Quibilan, Clarissa Reboton, ZT Richards, AD Rogers, J Sanciangco, A Sheppard, C Sheppard, J Smith, S Stuart, E Turak, JEN Veron, C Wallace, E Weil, E Wood. 2008. One-third of reef-building corals face elevated extinction risk from climate change and local impacts. Science 321: 560–563.
Eldredge, N, SJ Gould. 1972. Punctuated equilibria: An alternative to phyletic gradualism. In Schopf, TJM (ed.), Models in Paleobiology. Freeman, Copper and Company: San Francisco. 82-115.
Eldredge, N, JN Thompson, PM Brakefield, S Gavrilets, D Jablonski, JBC Jackson, RE Lenski, BS Lieberman, MA McPeek, and W Miller. 2005. The dynamics of evolutionary stasis. Paleobiology 31(5): 133-45.
Estes, S, SJ Arnold. 2007. Resolving the paradox of status: models with stabilizing selection explain evolutionary divergence at all timescales. The American Naturalist 169(2): 227-244.
Fukami, H, AF Budd, G Paulay, A Sol, CA Chen, K Iwao, N Knowlton. 2004. Conventional taxonomy obscures deep divergence between Pacific and Atlantic corals. Nature 427: 832-834.
Fukami H, CA Chen, AF Budd, A Collins, C Wallace, Y Chaung, C Chen, C Dai, K Iwao, C Sheppard, N Knowlton. 2008. Mitochondrial and nuclear genes suggest that stony corals are monophyletic but most families of stony corals are not (Order Scleractinia, Class Anthozoa, Phylum Cnidaria). PLoS One 3(9): e3222.
44
Gould, SJ. 2002. The Structure of Evolutionary Theory. Cambridge: Harvard University Press.
Hansen, TF, D Houle. 2004. Evolvability, stabilizing selection, and the problem of stasis. Pp. 130-150. In M. Pigliucci, and K. Preston, eds. Phenotypic Integration: Studying the Ecology and Evolution of Complex Phenotypes. Oxford University Press, Oxford.
Helmuth, B, K Sebens. 1993. The influence of colony morphology and orientation to flow
on particle capture by the scleractinian coral Agariciaagaricites (Linnaeus). Journal of experimental marine biology and ecology 165(2): 251-78.
Hoegh-Guldberg, O, PJ Mumby, AJ Hooten, RS Steneck, P Greenfield, E Gomez, CD Harvell, PF Sale, AJ Edwards, K Caldeira, N Knowlton, CM Eakin, R Iglesias-PRieto, N Muthiga, RH Bradbury, A Dubi, ME Hatzilios. 2007. Coral Reefs Under Rapid Climate Change and Ocean Acidification. Science 318, no. 5857: 1737-1742.
Hunt, G. 2006. Fitting and comparing models of phyletic evolution: Random walks and
beyond. Paleobiology 32(4): 578-601.
Hunt, G. 2007. The relative importance of directional change, random walks, and stasis in the evolution of fossil lineages. PNAS 104: 18404-18408.
Hunt, G, MA Bell, MP Travis. 2008. Evolution toward a new adaptive optimum: Phenotypic evolution in a fossil stickleback lineage. Evolution62: 700-710.
Jain S, LS Collins. 2004. Trends in Caribbean paleoproductivity related to the Neogene closure of the Central American Seaway. Marine Micropaleontology 63(1-2): 57-74.
Kucera, M. 2007. Chapter Six Planktonic Foraminifera as Tracers of Past Oceanic Environments. In Proxies in Late Cenozoic Paleoceanography, Volume 1:213-262. Elsevier.
Lieberman, BS, and S Dudgeon. 1996. An evaluation of stabilizing selection as a mechanism for
Lutz, BP, SE Ishman, DF McNeill, JS Klaus, AF Budd. 2008. Late Neogene planktonic foraminifera of the Cibao Valley (northern Dominican Republic): Biostratigraphy and paleoceanography. Marine Micropaleontology 69(3-4): 282-296.
McNeill, DF, JS Klaus, CC Evans, AF Budd. 2008. An overview of the regional geology and
stratigraphy of the Neogene deposits of the Cibao Valley, Dominican Republic. In
Nehm, RH, AF Budd, eds. 2008. Evolutionary Stasis and Change in the Dominican Republic
Neogene. New York: Springer. 21-45.
Nehm, RH, DH Geary. 1994. A Gradual Morphologic Transition during a Rapid Speciation Event in Marginellid Gastropods (Neogene: Dominican Republic). Journal of Paleontology 68(4):787-95.
45
Roopnarine, PD, G Byars, P Fitzgerald. 1999. Anagenetic Evolution, Stratophenetic Patterns, and Random Walk Models. Paleobiology 25(1):41-57.
Sheldon, PR. 1996. Plus ça change — a model for stasis and evolution in different
Vaughan, TW. 1911. The Madreporaria and marine bottom deposits of Southern Florida.
Carnegie Institution of Washington Yearbook 10, 147-159.
Wells, JW. 1956. Scleractinia. In R. C. Moore, ed. 1967. Treatise on invertebrate paleontology, Part
F. Lawrence: Geological Society of America and University of Kansas Press. 328–
444.
Willis, BL. 1985. Phenotypic plasticity versus phenotypic stability in the reef corals
Turbinariamesenterina and Pavona cactus. Proceedings of the Fifth International Coral Reef
Congress 4:107-112.
Willis, BL, DJ Ayre. 1985. Asexual reproduction and genetic determination of growth in the coral Pavona cactus: Biochemical genetic and immunogenetic evidence. Oecologia 65: 516-525.
Zelditch, M, ed. 2004. Geometric Morphometrics for Biologists: A Primer. Amsterdam: Elsevier