Fish and Wildlife Research 13 Biology of North American Tortoises Edited by R. B. Bury D.]. Germano UNITED STATES DEPARTMENT OF THE INTERIOR NATIONAL BIOLOGICAL SURVEY Washington, D.C.• 1994
Fish and Wildlife Research 13
Biology of North American Tortoises
Edited by R. B. BuryD.]. Germano
UNITED STATES DEPARTMENT OF THE INTERIORNATIONAL BIOLOGICAL SURVEY
Washington, D.C.• 1994
DAVID J. MOIAPKA 161
Neonates: Mieain 8 LiDks~ the Life IIl8tories ofNorthAmerican'!brto.....
DaWi J. )Iorafb
Cali(omi4 Stale UaiN., llaIabIpamzz.Departmat ofBiolqa
Qnon, CtJli(omitJ 90747
Abiita....EaBaad.........«l,..o1d)..tbe__~IifiI.....af'tMNorthAmIrica~(GapINrw).Neaaa_baw~JQ1k...._hiPermetabolic,... PI*iD cIeauuIdI. aDd naporatift ..... dIaD MaI&~. SaaaJl tort.oIIeIdiI'Ir by ......... <......... aad lIMn rabaI& beq abIIl Hr aDdbealliww) rr....__ af'tIaIir lilterr.aiJ.y(tM...,..l. N l aadjuftDile....1dDIIiIJDaTbe bytbeldulta<........., Le..dmallaafromtbat1Pial~ ot&anaadaD of ..... ad,.,.. ......... ill~ oramaJkiIed oftano....... a.poetIc ..". be..m...... ill the1'NDI. Ll8t hiatmy modela of tarCaiIII ant OIl raw Jan of of""adultI, wtJic:b an iDadIquta &0 cbInc:tIriIe tbIIe .... with ..au.. immature....adloqli&t....ofadu1t:LAmocW • PI"'"tobeJpaplaba tbeclulMicDdureof pncipitata.l &lid~ ill ....... populatioDL AacordtaI to • bet-bIdaiaImodel,tbe~ ...of""'(~)aad.,......~,.)orlliaiJarlile tobelilDUM;batlbe~ottlle...ad__oftt.ecbIJemiI appcriaDlddiflil8&bt~haw"""" bat OCtile...or otmaA'!-..)didtmtle N...-.l tGI1IDUeI twicetheweilhtor ..,... The fila toI...... ita 1lIIYbe.,..,... to thenlatiwIJ banb, ftriabIt oftenutriallifa.
a:. ........ Bet bed..... --.IIMICW. ........tal .... 00pMrut. batcbliqtortoiIu, repnduc&i.. dbrt.
Ega aDd. neoutes (<1 ,... of ap) are the • 8l. 19M). 'lbrtoi.MI do DOt have COIIC8Dtra1ied.leut-well·doclJmeDt8cI.... ill the liw. aCNorth ......arlJDCbnDo-........ofbItebHnpAmerican tortDi8a n.. miui..,liDb CCIIIlpi."O- that facDitata _diM of DIItiDI in _ ...mile ef!'ortt to cbarac:teriu life b.iIt:.orYe fill" mod- (Bendricbcm 1981; Mortimer 1982). ~watereliDe uui m.n·linl t.ort:oiIeL~ tWd Itudie8 ..,.ud turtIM an between theM two utalllNS;rnealed a ac:an:ityor.... lMOIIateI. udjUftDilM t:bIir t8rremialneR"'are uaualIynot fill' tram(Bura- 1978i DoqJua 19'18; Judd. aDd McQueen IIbore«100m>uulaftlDiDncapiable nIIIt:rata1980; SbieIda 1880; Berry uul 'nImtr 1888; Die- of Mec- aDd IUd ban CBmR IIlCl Barbourmer 1986; Adat It & 1988a; 'Ibm 18M; WilIOIL 1972; Coqdon et al. 1983: Wilbur mel~
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wiDtar. But. ill a few ..... thm'e may be • I8CCIDdaDd aipihat iftwval betwIeD pipiDa of the ..IbeU aDd actual........&om the DIIt(GibbaaaaDd NeJ80n 1178). TbiI pheaomeDon hu a1Io beenDalBdiD tbe......._ tarde (CarwIta ccuwcto;Chri8tea8 1990),ADotberUlliqlae~of1flUDllDeODa_
DUlYbe theDeUtralpHoftheirMmaacbltbatfoatersfermenting 0( mp.ted lIIIUftIheI • in batcbJiDa'~ ipono mo"er 198U). IDa-tion ~ JIOil arfeces to oc:cur ill 1MlOD&&al desert tonoiIesthat in the ran ill the )(oj... DesertClLJoyDer, CalibDiaStateUDi~DomiapezBiJbI. Canoe. pII'ICIDII1 COIDIIlvnbtion).
JUftDi1e Bo1Ian tom.... (G./14~)c:natIld~ tnilI at the opeD.iDp of IhDrtburrowa UDder __ sbnib Clnopies (8IpedallyOpruatio cactwI) into open a....,18D8I'81lY IkirtiDa the periphery ofedible V818f;ation ('Ibm 1994),Soae oftbele tzoIiJs may apoIIIt the youq tortoiAto~ microc1imatic streu, or biIh~orpuhaocut.aaeoua water loa. Ifoweftr. their hiPIUl'f'Ee.to-wlvme ratio may allow ueonates to ereficfeIltl,y t.hermonIaJate in cool ea'riroDmeD.ta.NeDDatelipowi~_..earJi..witbiD the calen·dar year aDd within a IiDIle clay than their adultcounterpartI <'l\IrMr et Ill. 1986). The early emerpuce D supported by obeenatioDa of EIYPfian~ (7atado iIeinmanni)-a amall.med species that uhibita early seuonal. behavior aDdmuch winter utivit.y-4iom Iarul'. Nepv Desert(Geft8n..MeDdelaIlDlm 1988).
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'1WIIeI.CamperitaDaf~~or....~-wJadNortb.Am8ricantortoi8u (GGP-w .pp.). Data Jaqely fromCoaadm .... GibbaDI (1186, 1981, 1180) aDdQenneDO Q8N}.
of bacteria and ftmgi to tbe ,aJk IDUI CWeiDbeq1984),
When the absorption of the yolk 1DUI is campleted. the emerpnt tortoise (aboui 40 DUD lmt8>extended its lencth by about 201(, from fetal dimensions in the .. Ihe1l <D. Montka, 1lDpUlisbecl data). Nuclear mapetic imapry indicatesthat even several mcmtba~ b.tc:binr the ,JG1k Punt:tionol and ComporatirJe MorpholDllYmus_.remains recopizabl. intemaJly (M. A.Joyner. Ca1if'ornia State U~_ DomiDIuez The Iize, shape. auul kiDatb of the ...ta1Hilla. Carson, penoraal commUDiadou). Belidual IIheJl help addnsa .... aucb .. minimal viableyolk lipid could provide a wiU ranpofoptioaa lor 11K"andpucIomarpbamainsmaU-siucladulta.the timing (Be8fO".Jjty) or 8JD8l'I'IIlC8 (GibboDll The deveJopmem ofmezbnwn..width in cheIoand Nelson 1978). Dlau ia 1imit8d by tt- caaatninta or the ....
Evidence of oV8'l'WiDterinl by embt)Oii or IUtO- pe!w.(CaDa*maDdGibboDa 1985,198'7l.Arepeenates of desert tortoi8es (GopMru ",im1 in aioD of..width to body me (after CaDa*m adNorthAmerica is limited (Grant 1936; Lllekmbleb Gibbou 198&) pnJjeeta aD..width of 15 DUD tor1982). SimilarlY. NODateI of the Jeopud tortoise the amall_ North American emJdid, a.mm~(Gfot:h«o1utpartltW.). a lup tvnoiM oftemperate ~. which is a freahwater tarde aboutsoutbem Africa. may spend 4'12 ..,. betwwn ... 90 DUll CL (Carr 1152; EmItadBury 19'77). Thedeposition aud. the _puce from ....(JIC- actual..wicWI ofc. """'1IbetP ill 14-16 DUllq,- 1969). In IIIOlIt eues, tbe loDe iDterval D <Erut azul Barbour 1972). The pelvia ill tortoi8eIaplained by a Ioor dia,... in~ in IDQ'baftnolVlldatrca:tandpropoI't:iaDatoaebtne
W92-t461 fWR 131 C1Ip. t51 MInjb 1P1 +2M41 PZ '"100M 1P3 1·lH4
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a pit that elnatea the IbeIl tal' 0ftI'lud. 1DG98I. IlouIul DO UIII1:JIia that ida*iliecl the 10wer 1imitaoftbe..wicltb in~ In the .pecIded Cape.toiIe CHCIIJIOPIM ....) ofMrb, tile 1UUl..width illO.llDIIl<8o)caUaDClBoaquiu 1188>,wIDch it ...... than tt. width·of ... ill other"'v'injclaof~tbe....."(81mmCL).The.,widdl it abom 1.3 __ larprinB. .......tbua inc.~. '!be larp to bepoaibl...... the poRariar lobe al the feJuleplutroaainHomopaan kiDItic uui abdaatlICl foro9ipoaitioa. Similar pauift abducdoa of thexipbiplaatroa bu been~ otthe ...eQeet orthe North Amerieaa tertDiIIe, GopMru 6riPadim (Bole and Judd 1991). A pIuticity oft:bl..has a1ID bMn f'ouDd iDN....<RoH 1982; I'cIia1963). and the pli8biIit)'aftbe parebalentegsbe1lmay be UDique in teatudiDid8 (Ewert 1985).
The pater width altha tortoiII8 ...may be arespoDM to selection for a Iaqer necmaal tort:oiIein Ii8I'l"eItrial enviroDm..ta. I'or example. thereare poIitive relatiou betlll86il iDCNUId lIUni~
Ihip aDd 1arpNUed... aDd Jarpr-1iztMl hatchlinp in cbehmi'DI (Swmllmd 8Dd Coe 11'19:hert 1.; WIlbur aDd Marin 1888) ad ipanidliIarda CFfilJW*lii aad BobI_D 1978; Sm.w aDdHu.yl99O).SeleetioDmayaUlofavorap8tVJQltresene with which aewbom tortoias can meetW1C8l'tain~CQIlditioaa.
DiIIimI b1 may DIOD&tal tDrtoiIea beliDllOODaftwemelpuc:a fivm the Deltflbm 18N)aDdcompouadI the .... fbr limb ItiniiiItb. Lupr ,...are prabIb1J &lao subjedad to !ewer .... hIDsmaJl pndatms (rodent&, .... reptilee, bin!I) andhaw a Iowr surface.tD-9OhuDe ratio, wbic:h ncluceI the rate atwater __
1IMMer. terreItrW lifeaJaoe iudlquatetoapIaia the adaptatioDaat1lqv UIIlbatch-Iinp.Boxturtles(pnUl~)ueat6uwtriAlpoup ofeDlJdida bu.t have..n ....<OaiW.)aDdnermatll Cmus about 7 r> libothereIIlJdld turtle,(CoaaQaDaDd<libboI.l885.l98'1; DondFudX8lth1880). their cbeIt relatiwe. Herbi~ ma-.dlridity or Ubi_t. aDd ro.orial behaw.- may deJUDd .... &om GopIIIru ......_. which havepea-m&II (about 30 r> tba AeODUeI ofaqaaticturtla
IDCNMIClIiM app8l'8lltly c:ontributeI flo .. It-~ ofaD inlDVirauuntl with lICUI:e
low-6ber (Demmat azul Van SoeH 1985).
DAVID J. KoIlA.PKA 166
For aampJe. diet~ jzuticad that daertipaDa~ dtnalU) are herbiwrouatbraapoat ute ()Iaata ud Nq,y 1987). NlODIIwJliaaN8 II8IIl to .u.et .....n pJat.... that areJaw ill Iber ClODtIDludlDllY '-ciJitate mee:blnicalma-tiaD a4cbaricaJ _irnflation offooda. SomeD......Jaquatic~ (nebu tbe 2C).mm-Ioa,~ 01P.utllnV- ......) aN .. herbi".... (Balbl.,DD ..VaQlbu 1911>. '1bII DeeM
11171D8CImdCl8J eIIbrt for MtiDc the hiIbly IbrouICCIIItat ofmolt tIIftItrial plaDta ratber thaD herbi9aryitMlffawn.larprliaaoftortoiBeDeODaieI.
Lazpr...aDCl.....oftMtudini.da~be.. c:buMeIIr..that an fiDel by MJectioDoper""_ tbemmmon......ofthe tortoiIeLOateo1oIioal UIl~l cJw.ten suapat that tMtudiDidI are dIriftd from tha betiprid faDDb' ofturtlu., pouibly aDCHton aftheAaiaD bax turtle (pnaa Cuoro; Ga&eyaDd MeyJan IB88). RelaUwly1uIaaDdbrittle ahalled. ....are • IJDivenal characteriRic of taatudjDidi uultMir baUprid etelton (E. KoIl, Butam nnDOia UDiwrait); Urbau. penoaal coauauaicatioD). PhyklpDeti~larp .... aDd DeODateIan IYIlplUomorphic: to t.o1'toiIeI and may be'ViewBd ..Bad traits. ,
The ph_aDD ofhetmucbrony ill reptilee baaalia beeD1araab"~Acti&reD.ti.al ODtopDy
atbody puts occurs in smaIl-sized lizards. iDclucim.1DicrcItaiidI (PnIcb 1980) aDd ICiDridi (Griffth1991). c.n.p.ea aDd pIutmn kinaa'i are eommOllIn uaaD.-IIiIerl .,.. or c:beloniana CRicbmcmdlBM), oftbMe Itate8 JD8¥ be pudnmor-pbic (..... JdJaMf. ma,y be a ftmdamfttal cIiaracteriItic ofJQaDI fDrtDiIII).
I haftDOt fiNDd a redadioDmthe enal apertuJeof DeOND' a1fdar tartlea~. IC'I'ipIcI ...,.,.,l. limiJ·r to a wl\1Jltar,f nBpOIII8 in jUftllile~(O.~aDdG...izii)tbatreducu tb8 aalpp bebaMll posterior maraiDa ofthe carapace ad~ AdDwnwanl addudioGofb paMedar caraplCllI8JII8 til be mOlt napoDlib....tUkiDemI I~ that tba IlDIItradioDZ'ICi1aI the ........ laP by .. much u 5C)(I, inG.~ aDd. OCCUI'I tbrouch the seventbyarafUte.Ro....., tbe e UtmNl!81 medgni..Corthe 0IIIl&nctiDD. ia UIIbawD. )IIIZ'tly ...... theclneIoJIIUDtal ...., of tortoiI. baa beaDJarael7 delcriptift rather tbul bilJl"4riwni':8l andmnftaed to tba Bwopeu.,.,.<Ewert 1985),
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168 FlsBANDWlLDur& RBSBARcH 13
Molt IZU1l tortoiIeI alIo exhibit abell kiDeIi.,eepedaJly in the poRarior plutron (Pritdwd1979). Not all of tbeR reported kius••• are ueceauriJ.J or ttDtirely pIUIdamarpbic. 'l1Ie 01IIII$ ofeuapMe kiNlillate in the CIIltoI8D1 atAlrH:aD hiDpbacked tortoi.e. (pnu. KiIaiz)w) and theprGIftIIift tJaibt1_ aad. fla1;tenj." ofthe Afriampmeeb tortoiae(j(~... tom;'i) ... DOtparaiDllftDioua with aimp1a paedomarpbic upleN_tioD8 (ObIt 1988). P8rbapI the ODtopDy ofld"Nilin tbeIe taD provieJel little or DO evideDce of~erochroD~
Sinrilady.hiDpaiDlCIID8emydid~(7IrrrapCM ad CuDnI) IIJd ill mud turtI_ (lriwM'ltea'Did81have DOt ... attribu:tlld. to jUV8DiJe ardiMJWIeDta.SoftIIbeU turtles (trioD.Jchids) nlpneeDt a specialNdud:ion ofBbeU aaiftcwtinn that lead to p1utralt1apa that may be p88damorphic cbaraden. Someshell tJaihiJity may be a aeemdery (pIeiDtropic)~ of small Ilia III jUftDi1es ucl smallspeci8s. autppeontnu:t:ioDImayreduce the dam-... fram pecIrinc 8Dcl 1I'iDg attacb by m..nbirds. rocleme. end iDwcti The J....... ofxiphiplaatnm ki....~ permit oviPMiticm of1arp .... in adult femiJ. of smallipeciel CBoIeand Judd 1991).
GopMnu AI eubIpecieI of G. polyp1wnwa (Wermuth and Merteu 1961>. Studies ofmoleeuJlr pDIItia (Lemb 8& al. 1989) aDd sheD. marphometric:s(Germano 1993) indicate that weU~t.edpopulatiou of G.,.,..;zu eDIt. Northern aDd_tbml popaladoDsufG.~.ape~ jueniJeI. di&r in carapace eolor CMontka1981), SjmiJlrly. juftDi1e deeert tortoiae8 in theM.qjaftDelertpoerallyhaveputerretioa oflhelldepth to IeDpb. IDDI'8 mid IDd c:ontrutinc carapeel coloration. and more IDgU1ar or eYeD dentatemaqiDal....oftbeeuapacetbanjuwnilesiD theSoDonDDeIert()(.A. JoyD8r, CaliforniaStateUni~.1Iit& DomiDpa HIlls. Cuaoa, IIDCl D. Moratb.1IDpubHebed data), Like the epiny turtle CHeoem,sqinGm),a batapridtromSoutbeaatAaia. tortoiIesin the Mojave DeIert teDd to have their IlDIUlarIIlalIiJuU ndw:ecl early in ODtopny {Obst 1988>Thus. it may be delirab1e to develop a dielDOIIiI of....tortoiaeI (GopMru) based. on variation aDdcWfenmces in juveDile characteristics
Population Ecology
The recn1iillumt or necmata is a key to understandin. the local distributicma of tortoiulI. 1001-
Systematics term tl"eDdsoftortoiaedeDsitiell. andcaaual factarathat limit the co1oDiel. However. there are fewdataon ncruitmeDt of North American tortoieea (Qer..
RePmal varirm.ta aDd cryptic~ of North JD8DD 19M). Ace or size cia... are needed. mAmerican emydidaand trioDyc:bida are u.euUydis- recoaatructputrata andepiaad..ofrecruitmellt.tinpisheclmon easily from juftllilM thaD. from UDfortuDately, the S\ICCUI rates of emerpneeadu1!J. DefiDiDc chuacteriatica are ofteD variable (relative to total cIepoIited lIP> aDd. IW'Yiwnbipor obscure in adults ofcloIely relat.ecl1lqUaZ tar- of D80D81:ea and juveDile8 may require dec8deB oftIe.. but the colon BDd pUterDII of'juftllile turtles ot..: ,aticma or iJmofttiw breakthraaPa in datatacilitlte identiticatian (CcmaDt; 1978). For eum- ptberiDr.pIe, the Cuatro 0 ....... IIDftaheJl turtle (ApaIone Aa maD,Y U 10 yean ofnprodw:tlve e8brt mayspi7aiferu ater) wu deIc:ribedlarplyfnllll diapoe- be required for sw:eeutUl population rec:ruitmeattic cbarac:ten that were oaJy reliable in j11ftllile8 in GopMrva polyp/wIIJw (Anffimberg and IV8nOIl(Webb 1960; Manfta 19?'1). 19'79; lAnders at al. 1980) ... in enviIoDmIm1:I
The iderltifleadoD ofdiapoetic ch8rader _tell with relatively Itable dime_ aDd biab wptatiwof JOUDI tortoiIeI baa been c:DIJ8traiMd heea.. produdi'fity beca..BOIDe iDdividuali and popula(1) neooates are poorly k:Down aDd rareb' obIened tiau of this .ped_ may skip reproduction for onein the field or pnIIeJ"Qd in c:oD.ectioD.r, (2) the 1bur ormare yean. Two species oft0rt0iBe8 (G.~lII*iee of GopIatrw are allopatric (n«Inciq the adG.~)occar ill North Am.namDeed lot ripaua eIi.poetic byw); aDd (3) DO ... dellIia, where IUCCIlIfbl ncnitmeDt it probIbb'.... orany North American 1IartIUe haft been iDfnquentbecaueofwqndictableweatberillariddIIcribed. eaept in GlUt attempt of cIauir:YiDI an eDvirvnmeati CKoratb 1977. 1982; Germano
W92-146 I FWR 13I~ 15/""/ Pl ~1Z""1'2 6ot0.94/PJ 7·12....
1994), Arare ..of8Il'Viromamtal CODditimw maybe uces"ry fir the recruitment of tortaiIM- TheabIeIa or rarityofju.....u. ill populatloDa fbr 1-2decade8 IDAY DOt iDdicate recruitment failure inarid enYirolmleD&a. .Tbelaap9ityof~ tlmeCOMtnintaof
a&udies by p-aduate stada.ta, aDd. DlcoI:udsteDtftmdiDl of ..-..reb CDlllbine to make loag-termecolaIical m,di.. rue. Comparative life historielof all four~ epec:ieI may require 20-30years betbn pnci8e model, for rec:ruitmeDt can hevalidated withc:arrent techDoJoBy aDd. approecbet.
Neonates haft u IIWlY u 3 timas the .-tiDemetabolicrat.oI...3-,..-.old~""'(N'"and Bradley 19'14), aDd the dietIuy needa of ne0
nates are twiee that ofadult tortoiIa (1n, ftl'IIUB
ft,proteiaCODtent;AdMtetaL 1989b)aDdem,dida(~; Parmenter udAvery 1990), NeoDa_presumably have biIh"demand. Cor water' and zw.trieDtl8w:h u calcium <EIque aDd Peters 1994).
Neon-ta) dietary cIem-ndl"may be qualitatiwlyUDique u well. For upmple, DeDIUltel l6fIG1III.ipIIIG <Tro,v l.984a. !984b) have to aeqaire appropriate IOil microtlora ad iDpR 8dult.. forefBcient fermeDtat10n ofcell in the hiDd liltofthe Deon.... There a1Io to be a tFjpiftcantrole for such fermeatiDl auerobes in GopMnupolYPMmra CBjomdal1987). The bual metabolicrates are at least ODe order of JDIIIDitude lower intortoi&eB thanin m-mmlls ofsimil.rDIUI (Prouerand Brown 1968), '!be aurfac:e lldivity of adulttortoises may be ODly 1-2'11 oftbeir yearly activityeN. and Medica 1988;AdeK et aL 1889.).
'Ibrtoilel may aIIo haft Jup NMI..- ofblad.der water (Nagy and Medica 1986) aDd storedcaIori. in tissue (liver), wbU:h maybe ph)'JlioloPcal factors that buffer enY'iroDlllental stn...sora. These stores may provide a latent period ofleveral yeal'l between 1IDSUitable periocb anddemOll'8Pbic: respcmI8I in tortoises. Perbape acutegrowth riDp can be wred to document whethertortoises in strea perioda <I.,., drouahte) aremerely surviWli (DO arowth> or IJ'OWiq sliPtlYbued partly on resenea (Germano 1988, 1994).
Rec:ruitmeDt may also be tb8 key to cIetea lIIiDincwhether a population is within the~capecit1orim eDViroDment. WhendemoIraPhicdatan1yheavily on recorda of the adult ag. or siz.daises. there is little bMia to estimate dynamiccbaraeteriatics .pec:iaJly recnDtment. Criteria of
DAVID J. MolWl'KA 167
~ nprodud:iDn, aDd coborta (ace) mayal80 be UMfdl indicators of the miDimum caft)'iDIca~Alt:boalb these ePimason are more CDIII
pis tIumsimple Dumhen (e.l-. estimated density).tbey may be ucuoratIaDd ildbrmative me&BUr'M oftrenu. Some incticatan may b. inltructive:(1) blood ...... caD d8fiDe the atate of health()Ionfkaetal.1986); (I)81'D'.1 iDerementi ofeheJl~ can jDdjate the lIowth of jUftlliles (OerIIUIDO 1992); (3) the prlt..... 01' relative abundanceofjuveDile col-nel may be nideIu:e of recruitment(AdeBt tit; aL 1989a); (4) the pr..-e ofhetcbJinpmaybe evideDceofIUCCIlIIdbl repnldartiOD; aDd. (5)pafI-bleproteiD.c:ah:ium.JIUICrOIlutrieJlt8, andmicrahabitata <e.&-, friable IUbstratel) indicate re8OUl'C8S for DeODlt.el BDd juveDile tortoiIes.
AModel ofRecruitment inChaotic Environments
Natural enviromlumtl may have chaotic proe.... that do DOt & a 1iaear or invariable coune ofeventl azul thUi have UDpreclictable outcom...Tbeee chaM IlUld.ela haft already heeD UMful fbr!rimulatiDg dispenal and popuJatioD deuaitin ofarthropods (BupU et 111. 1991). Recently. LiebermuaDdMorafb Cl988)fouDdtbatphysical facton(steep slope, abeeDee ofan alluvial substrate, playaborden) ljmitM! the occwleaee and deDIitiee ofG.~buthmdDOOODIIistmtpredictorsofather bebitat variables. The patchy d1dributiiaIlof BolIOD tDrtai.- in a deMrt enviromDeDt·manc:Ja.ly reMlllbJes cbaaa model. than simple JiDeargrsdieDtl.
1b ap)-iD the patchy cUmibutian oftort.oilea, IdeftIopecl a eb80I maclel Cor recruitment, mach likethe ....,....- dispenal model (Brown end GiblOB 1983) that~ lacal weather paU:emIfor the spatiallC8~of pulive propquIM or......... ctilIpnaL Rather than ICatter wPeDeWreproductiveUDitI. the --.theI'paU:emltbem....... ecatter unpredictahly across a landRape oftDl1iaiBe demes that are relatively IItIIbJe in positionaDd reproductfDD. In the model. the local environ-~.~~d~of ~_..or....)tbatumally prodvce IID811clu~ oflarpeas (n.. W) fJ9V1 year. neD when nutriticmaln8DIJRII are ICIIDt (1UnuIr et al. 1986).
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u.cl G. Adat fOr mmmentl on thIt manWlCript.Muah ~ tbia Ie..... 8IplICiaDy the compuisoD. of~ and teltUclinids, refl8Cta the intIwtDC8 ofL Vltt aDd ........uata nwIeate ill IDa falll989heqIet.DlcJID' 1IIIriP·~ UDi••1ityatCalifbrDia. LollADpla, apri,)'"B. Aver.Jt B. Ben,D, ad C. Petenon. I tIumk J. Btmlnclu, S. Papedla.. aDdH. Peck aDd tor tac:bnial impauvemmt or theIII'DU.mpt. AD rapGDlibility for the preaenteclerran ad. opiniDDI ..... atlre1y with me.
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