4 - Measuring and Monitoring Biological Diversity. Standard Methods for Amphibians - Cap 2 -...

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Chapter2

AmphibianDiversityandNaturalHistory:A nOverview

RoyW .McDiarmid

Introduction Fewertebratesresependentnnviron-mentaloisturesmphibians,hoseeo -graphicanges,cologies,ehaviors,ndifehistoriesarestronglyinfluenced bythedistribu-tion an dabundanceofwater,usuallyin theform ofrain.nact,hebruptn d ftenynchro-nizedbreedingofmanyspeciesoffrogswiththefirstrainsisawell-knownnaturalphenomenon,especiallynreaswhereainfalls istinctly seasonal.Likewise,theannualbreedingmigra-tionsofcertain northtemperatesalamanderan dfrogpeciesoraditionally se dvernalondsarecloselylinked tomeltingice,rising tempera-tures,ndwarmpringains.nontrast,ow rainfall,umidity,hasesofhemoon,n d

multitudeofotherecologicalfactorsinteractto affectamphibianactivityintropicalw etforestsisotwellnderstood.u stwhen researcherthinksthatheorsh ekn owsthe"typical"situa-tion,somethingunusualorunexpectedhappens,hifact,in somecomplexassemblages of tropicalfrogs,thenomialpattem maybestbe described ashaoticrnpredictable.Theomplexn doften poorly understoodrelation betweenthebe-haviorndcologyfmphibiansndocalweatheratternsmakesesigning amplingprotocoloramphibians ifficult.ThisompU-cated interdependency issomethingthat users ofthisbookneedto keepin mind.The threeordersofivingmphibianscaeciliansGymno-phiona),alamandersCaudata),n drogs(Anura)areoundn arietyoffreshwater


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CHAPTER2

aquaticnderrestrialnvironmentshroughouttheworld(Table) .W hetherinshallowseepson steepslopesorburiedin decayingorganicmaterialatthe bottom ofbogs,indeepleaflitterin tropicaleveigreen rainforestorinbromeliadshighmtheforestcanopy,amphibiansoccurinnearlyverykind of terrestrial an dfreshwaterhabitat.

Mostpeciesav e iphasic,omplexifecycleFig.).nesponseoertainnviron-mentalcues(e.g.,first rain oftheseason), terres-trialdultsypicallymoveouitablequatichabitatstobreed. Followingsomeform ofcourt-ship,adultsofoviparousspeciesdepositeggsin ornearhewater.Theseggsatchntoree-swimmingarvaehatremajorconsumersnaquaticenvironments.Afteraperiodofgrowth,larvaendergometamorphosisndmovebackintotheterrestrialenvironmentwheretheyfeedan dcontinuetogrow.W he nmature,theyreturn tohequaticnvironmentoreed,herebycompleting th elifecycle.

Otherpeciesmdergoirectevelopment,thats,he yacknndependentarvaltage.Theireggshatchintononfeedinglarvae or smallcopiesofadults.Afew formsareovoviviparous or viviparous.

Anunderstandingofth edistributionsan d lifehistoriesofthespeciesunderstudyan dknowl-edgeofheabitatsnhichherganismsoccurareessentialto projectdesign an d toselec-tion fsuitableamplingmethods.Suchinfor-mationlsonhancesheffectivenessfsamplingand,thereby,theaccuracywithwhichamphibianspeciesrichnessn dabundancecan bestimated.nheollowingages rieflydiscusspertinentaspectsofthelifehistoriesoflivingamphibiansan dsummarizethebasichab-itatsusedbydifferentgroups.Ialsoprovidean overviewofthemphibian roupsikelyobe encounteredon eachcontinentan dtheirrespec-tiveabitatsTable).nceheoalsfbiodiversity rojectav eee nefinedChap-ter3),data in thetableshould aid in theselection ofsuitable inventorytechniques.

Consider,fo rexample,astudyoffrogdiver-sityatalowlandrainforestsitein SouthAmer-ica.Only3 ofapproximately0familiesintheregionhaveaquaticadults,an d2ofthesefami-liesPipidaen dPseudidae)ncludeeryew species.Thus,aquaticsampling should have lo w priorityifadultsareth etargetstage.However,ifan investigator were toinventorybothadultsan dlarvae,he naquaticamplingwouldbeppro-priate.Nearlyllamiliesav equaticarvae,an damplingorarvaemightumpurelyaquaticadultsaswell.O n theotherhand,adultsofsomespeciesin 6familiespotentiallyintheareaarearboreal,ndeveralofthesefamilieshavehighspeciesdiversity.A checkoftheliter-aturewouldshowthatadultsofnearlyllpe-ciesn fheamiliesCentrolenidae)re arboreal,butonlyinstreamsidevegetation,an dthatadultsofmanypeciesof2otherfamilies (HylidaendLeptodactylidae,speciallype-ciesin thelargegenusEleutherodactylus)occuraboveground,bu tonly in forest.Thus,thestudy design shouldstresstechniquesfo rsamplingar-borealhabitats,bu titwouldalso havetospecify transectsacrossor alongstreamsan d transectsin theforest.

Inmostnstances,esearcherswilleetterpreparedonitiatetudiesfhe yirstea daboutheeneralcologyndifehistoryofamphibiansikelyoeoundnherean dconsultriginaliteraturenpecificroups. Excellentummariesfertinentnformation ca nbefoundingeneralreferences(e.g.,Duell-manndTrueb986;Tyler989)rneo -graphically oriented publications(e.g.,AfricaSchi0tz975;Passmoren dCarruthers979;Lambins988,989;MadagascarBlommers- Schlsseran dBlanc1991;EuropeArnoldan dBurton978;Engeknanntl.986;AsiaBerry975;ngerndStuebing989;aedaan dMatsui989;AustrahaCogger1983;Tyleran dDavies1986;North AmericaStebbins1985;PfingstenndDowns989;Conantan dCoUins1991;MiddleAmericaDuellman970;Villa


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Diversityand NaturalHistory

1972; SouthmericaDuellman 1978; Cei1 980 ;Heyer et al.990) .

OrderGymnophiona(caecilians)Caeciliansareelongate,limblessamphibians;theylack tailsor haveshortones.Theyare pantropicalan doccurin mesic,forestedareasin allpartsof theworldexceptMadagascaran dthe Australopapuanregion.Livingcaeciliansaregroupedinto6 fami-liesan d36geneiEi;bout65peciesarerecog-nized(Frost1985,updatedthrough99 2by Frostan dMcDiarmid,unpubl.data).

Caeciliansaredifficult tosample because theyareaquaticor fossorialan darerarelyobserved.Becauseoftheirsecretivehabits,w eknowlittleabouttheirecologyrlifeistory.Malecaeci-liansav e edian,rotrusibleopulatory organ,an dfertilization presumablyisinternalinal lpecies.Mostcaeciliansre iviparous,l-thoughafewareoviparous;omehaveaquaticlarvae,whichlivein pondsor streams.

Therereowidelynownechniquesorsamplingcaecihans.However,methodsfo r cap-turingaquaticfrogs,salamanders,an dtheirlar-va emaybeuseful(Chapter6).Aquaticspeciesmay be removedwithadipnet from deeperpartsoffast-flowingcreeksat mid-elevations orfoundin leafmatsand shallowsofmeanderinglowland streams.Fossorialpeciesmayencounteredin soilbeneathpilesofrotting plantmaterials,in looseoi ln din eravellongtreams,ndbeneathlogs.ndividualsccasionallyareap -turedinditchesoron roads,trails,ortheforestfloor aftertorrential rains.

OrderCaudata(salamanders)Adultsalamandersareterrestrial,aquatic,fosso-rial, rarborealmphibianswithfourlegsnohindlimbsniren ids)ndamoderatetolongtail.MostgroupsareprevalentintheHolarctic

region,bu tamajor radiation ofplethodontidsal-amanderswithdirectdevelopmentha sevolvedinheNewW orldropics.Livingalamandersareassigned to10 famiUes,61genera,an dabout390 species(Frost985,pdatedthrough992by rostndMcDiarmid,npubl.ata).ala-mandershaveavarietyofcourtship patternsan danequallydiversearrayofreproductivemodes.Visualndhemicalignalseemoemoreimportantorcourtshipnalamandershann frogs.Mostsalamandershaveinternalfertiliza-tionwithoutcopulation,bu tafewlargeaquaticspeciesav externalertiKzation.ggsfaquaticpeciesreaidsingly,intrings,rin clumpsin pondsorstreams,sometimesbeneathstonesorattachedtoegetation.Thesepecieshaveaquaticlarvaethattypicallymetamorphose an doveo errestrialnvironmentheretheyeed,row,ndmature.Asdults,ne-sponsetopertinentenvironmentalcues,theyre-turnoquaticnvironments, ftenheirnatalsites,ndreproduce.om epeciesreerma-nentlyaquatic,an dlarvalmetamorphosisisin -completeobligateaedomorphs).thersrefacultative paedomorphsan doccasionally repro-ducewhileretainingcertainlarvaltraits.Manyspeciesmostplethodontids)reterrestrial,de -positclumpsofeggsin moistsitesin burrows,in leafjitter,orbeneathocksndlogs,an dhavedirectdevelopment;in manyofthesespeciesthefemaleparentattendstheclutch.Afewpeciesofalamandridsrevoviviparousr ivipa-rous,producingiveaquaticarvaeorfullyde -veloped(metamorphosed)young.

Salamandersareprimarilynocturnalan dhaveactivitypatternsthatmay vary ontogeneticaUy. In -dividualsmaybeclumpedordispersedwithinahabitat,ndpatial istributionsftenvarywithsexan dreproductivestatus.Somecommontem-peratespecieshaveasynchronousmigration from terrestrialhabitatsto aquaticsitesforreproduction.Becauseoftheirbundancendositionnhe foodweb,incertainhabitatssalamandersmay be themostimportantvertebrateorganism.For ex-


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CHAPTER 2

Table1.Ha bita tUtilizationbyAmphi bi a ns "North America^ Middle America South America

Taxon^ Aq Se Te Po Ar' A, Se Te Po Ar Ag Se Te Fo ArCAECILIANS(Gymnophiona)

Caeciliaidae A* A (2 4genera,89 sp.) V V

Epicriidae '"(2 genera,36 sp.)

Rhinatremidae A. A(2geneia,9sp.) L E

ScoleeomorphidaB *(2genera,5sp.)Tjphlonectidae : A (3genera,22 sp.) V

UraeoCyphlidae -,(1enera,4sp.)

SA L A M A N D E RS(Caudata) Ambystomalidae .4 A A

< 2 genera,33 sp.) L L Atnphiumidae A

( 1genus,3 sp.) L ECryptobranchidae A

(2 genera,3sp.) LDicamptodontidae A A

( 1gen,4sp.) LHynobiidae

(1 0 genera,35 sp.)Plethodontidae A A A A A A A A A A

(2 7genera,2+ 4sp.) L E D D D D D D Proteidae A .

(2 genera, 6 sp.) L Rhyacolritonidae A (1 genus,4sp.) L Salamandridae A A A A

(1 3genera,55 sp.) L L Sircniilae A

(2genera,3sp.) L

F RO GS(Anura)Allophrynidae A

( 1genus,1sp.) X TArthroleptidae

(7genera,73 sp.)Ascaphidae A

(1 genus, sp.) L


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Diversi tyandNaturalHistory 9

Europ/frica^ A.

D L E

A D

A A A LAD?

A L

A A AL

A D

AL

AAAAALAuslraliaAq Se T t Fo Arq Se Te Po Arq See Po Arq Se Te Fo Ar(Continued)


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10HAPTER 2Table1.{Continued)

N o r t h America'^iddle America' 'outhAmerica' 'Tajton*, Se Te Fo AJq Se Te Fo Arg Se T e Fo Ar D? A AAD?Biachyeephaiidae(2 genera,3sp.)Bufonidae(31 genera,35 6 sp.)tCentrolenidae' ELAALA A AA

ALN DL

(3genera,8 8sp.)Dendrobatidae

(6 genera,14 8sp.) -D Discoglossidae

(4genera,15sp.)Heleoptirynidae

(1 genus,5sp.)Hemisotidae ^

(1genus,8sp.)HylidaeA A A

(3 9genera,6 8 6 sp.)LLHyperoliidae

(1 9genera,22 7sp.)Lelopelmalidae

( 1genus,3sp.)LeptodactylidaeAAAAAAA

(5 0 genera,81 3sp.)EDEDDDVL DL NMicrohylidaeAA(6 6 genera,30 8sp.)E DNMyobatrachidae(2 0 genera,11 4sp.)Pelobatidae(1 1genera,89 sp.)Pelodytidae (1enus,2sp.)

Pipidae(5genera,27 sp.) L

Pseudidae(2 genera,4sp.) L

RanidaeAA A(4 8 genera,6 6 9sp.)Rhacophoridae(1 0 genera,19 7sp.)Rhinodermatidae( Igenus,2sp.) LB Rhinophrynidae(1genus,1sp.)


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Euriqie^ Africa'^

DiversityandNaturalHistory 11

Asia AustraliaA, Se Te Po Art, St Te Fo Arq Se Te Fo Arg Se Te Fo Ar

A AAL L NVANA A A

L B BA A

L BA

L

L

L

A.

AE

A A AE E E

A AL ?

A A A A

A AN N

AAAAAAAAAD L L N ? ? D D D AAAB LLD D AAL

A A AAAALNE

ALAAAALLLALEEEL A A L

(Continued)


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12 CHAPTER2

Table1.(Continued)

ftxon"Sooglossidae

(2 genera,3sp.)

N o rt h A m eri ca Middle America South Amo'te a Aq Se T e Fo Ar' Aq Se Te Fo Ar Aq Se T e fo

'Onlynalurallyoccurringspeciesarescored.GeneralSyaspeciesisscoredonlyoncean disassignedto thehabitatthaimosttypifiesthelifehisiorytage;xceptionsrealamandersha taveopulationsha treacultativelyeotenicndopulationshategularlyndergo metamorphosis.Adashsignifiesthatthe taxondoesn ot occuronthe continentindicated. ''Family designationsan dthe numbersofgeneraan d speciesfollowFrost( 1985)asupdatedto1992 (Frostan dMcDiarmid,unpubl.data).

Includesthe UnitedStatesan d Canada.IncludesMexico,CentntlAmerica,an dthe Caribbean. IncludesTrinidad.Includesthe areawest of36 "E(see Amoldan dBurton1978).

ample,n orthernardwoodorestnN ew Hampshireheeastemed-backedalamander{Plethodoninereus)xistsnensitiesp-proaching 2,500 perhectarean d convertsenergyintoewissuetbout ,000/kcal/ha/yr.tsstandingro p iomassofabout,650 /h asabout2 .6 timesthebiomassofbirdsinth eareaatthepeakoftheirbreedingeason,an daboutequcilto thatoftheshrewsan dmice(Burtonan dLikens975).Incontrast,certaintropicalarbo-realalamandersrencounteredn lyarely,when romeliadsreemovedro mreesndsystematicallyearched.nfortunately,his sampling methodalsodestroystheir habitats.Thediversityofalamanderifehistories,behaviors,an d habitatpreferencesnecessitatesadiversityofmethodsoramplingpopula-tionsndestimatingheirizes.Fortunately,salamandersreeasonablywellknownn d,exceptforsome tropicalspecies,easily sampled.

OrderAnura(frogs)Frogsreumpingmphibiansithlongatehindlimbsn doailsal larvalnuransnd

maleAscaphusrueiav eails).Theyrehe mostdiversean dabundantgroupoflivingam -phibians,reosmopolitann istribution,ndoccurin essentiallyallterrestrialan dfreshwater habitats.heirpeciesiversitysighestntropicalw etforests.Taxonomically,livingfrogsareistributedmong5amilies;urrently about33eneraan d ,843peciesrerecog-nizedFrost985,pdatedhrough992yFrostan dMcDiarmid,unpubl .data). rogsm ay bequatic,errestrial,ossorial,rboreal,rsome combination thereof.Some arediurnal, bu tmostarenoctumal.Adultsofmostspeciesre widely ispersedinthenvironmentxcepttspecifictimesoftheyearwhentheycongregateataquaticsitestobreed.

Vocalization is an importantcomponentofth ereproductive behavior ofmostfrogs.Amon g ter-restrialertebratesperhapsllertebrates),frogshavethehighestdiversityofreproductivebehaviorsn dparentalcareknown.Breedingm aybeexplosive(synchronousoveron eorafe w daysataquaticsites)orprolonged(spreadoverafewweeksormonthsataquaticorter-restrialsites)[W etis1977] ,Mostspeciesbreed onlyonceeachyear,butcertaintropicalforms


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Diversi tyan d NaturalHistory 1 3

E u r o p e Africa^ Asia" Australia''l Se Te Fo Ar Ai Se Te Fa Ar A

BD

Aq Se Te Fo Ar Aq Se Te Fo Ar

IncludesMadagascaran d theSeychelles.Includesthearea eastofEuropeto W allace'sline.

Includesail ateaseastofW allace'sline,includingN ew Guinea,N ew Zealand,an dcertain PacificIslandHabitats:Aq = aquatic;Se = seniiaquatic;Je =tetrestrial; Fo= fossorial; Ar= arboieal.

groups.

Lifehistotystagesan ddevelopmentalmodes:A=adults;E=eggs;L=larvae;D= directdevelopment;N=nidicoiouslarvae(nidicolousendotrophs ofAltigan dJohnston1989) ;V=livebirth,ovoviviparousor viviparous species;B="hrooded"eggsand/orlarvae(attachedto or in somemodifiedstructuree.g..pouch] fadult),equaltoparaviviparousan dexoviviparousendotrophsof Altigan dJohnston{19S9}.Linon ehabitatwithno Einanotherhabitatindicatesaspeciesthatplaceseggsin the samehabitatinwhichthe larvaeoccur;an Ein the arborealhabitatan dLinthe aquatichabitat,fo rexample,indicatea specieswhoseeggsare placedonleavesan dwhosetadpoles,on hatching,dropintowatertofeed.D? or L? indicatesthe habitatin whicheggswithdirectdevelopmentor eggsan dlarvae presumablyare placed,hu tdataare lacking,

arereportedtobreedthroughouttheyearwh en -everconditionsarefavorable.Mostfrogshaveexternalfertilization,aquaticeggs,an dfeedinglarvaecalledtadpoles; amajor reorganizationofthe tadpoleduringmetamorphos i s distinguishesfrogsfrom mostother amphibians.

Femalesf ewpeciesepositggsnleafitterorw etmoss;heggshatchntononfeedingarvaehatundergometamorpho-sisthees tite.dultsfotherpeciescarrytringsfggsrappedroundheirhindlegsortransporttadpolesfromterrestrialsitesoaquaticitesnheirbacks.n fe w species,emalesplaceadpolesnwaterheldinbromeliadsan dthenreturntofeedth ear -va eithonfertileggshatheyeposit.Manypecies,especiallynheeotropics,havedirectdevelopment(n ofree-swimminglarvaltage).hesepeciesepositggsnmoistterrestrialorarborealsites;afteran ap -propriateeriod,heggsatchn tomallcopiesoftheadult.Somefrogsbroodeggson theirbacks;othersbroodeggsortadpolesnpouchesnheiracksrides,nocalpouches, revennheirtomachs.Someof

thesebroodingspecieshavetypicalaquaticlar-vae,butmostexhibitdirectdevelopment.Al-mostveryeproductiveode,ncludingnonplacentalviviparityan dovoviviparity,oc- curs in frogs.

Theig hpeciesiversityfrogs,heirvarietyfifeistorymodes,n dheideassortmentofhabitatstheyuseposeasubstan-tialchallengeoheesearchernterestednsamplingheserganisms.ortunately,he aquaticbreedingbehaviorofmostspecies,thepervasivenessofth eaquaticarvalstage,ndth epeciespecificityfeproductivevocalizationslloworffectiveamplingmethods.Amphibian larvaeMost amphibianlarvaeoccurhi aquatichabitats,includingovingaterstreamsndivers),stiUwater(pondsan dakes),an dphytotelmata(treeoles, lantxilsndtems,romeliads,an dsoforth).Terrestriallarvaedevelopin moistmicrohabitatsuchsmoss,nderndwithin


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14HAPTER2


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Diversityand NaturalHistory IS

decaying logs,an dinhollowsinstemsofplants(e.g.,bamboo).Therelationshipsamongdevel-opmentalmode,larvalmorphology,an dhabitatofanuran tadpolesaresummarizedin Altigan dJohnston(1989).No comparable publicationex -istsorsalamanderlarvae,lthougheferencesto ifferencesngilltracture,od yform,n dfinshapeamongstream,pond,an ddirect-devel- opingformsarescatteredthroughtheliterature.Littleisknown aboutcaecilianlarvae.

Amphibianarvaeftenreoundnargeconcentrationsatbreedingsitesoverlongperi-ods.Asaresult,samplinglarvae m ay be amoreefficientan dquickermethodornventorying

speciesatasiteha namplingdultsGascon1991),venhoughggsndarvaeofmanyspeciesarepoorly k nown.In fact,fo rmanyspe-cieshesetagesreeasonablyellocu-mented,n dmorereeingescribedveryyear.In addition,collecting vouchers of amphib-ianlarvaeofteniseasieran dprobablyhaslessmipacton thepopulation than collectingadults. Even thoughlarvalsamplingmay be somewhatdestructivefertainquaticabitatse.g.,pondswithense,ubmergedquaticegeta-tion,orbromeliads),itshouldforman integralpartofan y sampling program.


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4 - Measuring and Monitoring Biological Diversity. Standard Methods for Amphibians - Cap 2 -...

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