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Tramtutious t& thr Royal Society of S, Aust, (1944), 118(0. 53-57. CLIMATIC CHANGE AND ITS IMPLICATIONS FOR THE AMPHIBIAN FAUNA by Michael I Tyler* Summary Tyler, M .1. IW4) CIimaliechangeand its implications flu theamphibian fauna, Trans. R Sot: $ Ami. 118(1), 53-57. 31 May. 1994 The dependence offrogs upon moisture make* them highly sensitive toenvironmental conditions. The South Australian frog fauna includes28 speues whichcollectively and individually experiencesawidetemporal range oftemperature and availahle moisture. Any climatic change involving warmerand moislerconditions is likely tu enhance their distribution and abundance Krv Words; Fro^s. moisture, distribution, South Australia. Introduction from fewerthansix localities, andeachspecies is more widely distributed outside the State. Numerous frog The relevanceo\'thestudy offrogs many evaluation species in South Australia are at the geographic limit of the impacts of climatic change hinges upon oftheirdistribution, and climatic change may have a recognition of the dependence ofthese animals upon dramatic influence upon their persistence or moisture. Nevertheless ihe survival offrogs throughout abundance. the period lhat witnessed the entire evolution of ad olhct terrestrial vertebrates,demonstratesthecapacity of frogs to survive massive environmental changes. T.J»mr I: Geographic<!ntrti<1cn\iii\ "ji'SouthAustralianfw$ The complete extent ofthe diversity ot the modern fauna. frog fauna is unknown: Duellman (1933) estimates a total of3967 speciesat3Lxii 9U andnumerousspecies Species Known from Numoc-ruf sronlmedto Ices thanua have heen described subsequently. In Australia the Geographic Area species lhatarea l«alitlfi current total is203, but many moreawaitdescription. Despite Ihe success and longevity of frogs as an Northwest 9 s 5 evolutionary lineage they remain dependent upon Northeast 10 5 5 moisture because of the relative permeability of the fFl.virnedePresniRnasmuileas 53 o1 8 skinand (in most species) the need to deposit eggs in Yorke Penmsuia •y 1) free bodies of water. Ml Lofty Ranges 7 Murray Vallev 9 3 Il follows lhat frogs arc highly sensitive indicators Kangaroo Island 6 of environmcnial pollution and, equally, that they Lower southeast 11 4 fl contribute an early warning system in terms of Nullarbor Plain T detecting environmental changes. Anyclimaticchange mSouth Australiaat aregional Impact of Rainfall oi total level is likely lo impact uponthe distribution of species, and upon the number within this Stale. Although the amount of rainfall and its reliability are not the only factors influencing frog distribution, South Australian frog fauna the generality can be made that the persistence of moisture at or near ground level is most important. Currently 28 species of frogs have been reported trom South Australia. The largest numberofspecies To predict faunal impact in South Australia it is cwinohmiapcnahyraaisrbelaaels(no11u)tmhibesetraosrebaaercoffofuohnuidnghdiensitnthtrehaeilnfoaarwlieldr.nsHooorutwthheweveaessrtt apiserlataitpnirteoungdtrientsaolseixvgareamidiinnecenrtea.asgeTeohogerrdaoepncheriecaarasereaeainiinnraAwiunhsfiatclrlhalatilhaoenrigen (9) and northcasr (10) (Table 1). which this requirement ismet isthe NorthernTerritory, The northwest andthenortheastarc alsotheportions of South Australia where numerically and wherc there isaprogressivereduction inannualrainfall proportionately thereaxe the most species not shared from north to south (Fig. 1), with other areas (Table 1). In each instance these The Northern Territory model "unique" species arc known within South Australia •' Department of /oology. University of Adelaide, South Baseduponthedistributionpatternsofthe42 species Australia 5005. then known from the Northern Territory plotted by 54 M. 1YI.LR J. m 3ii m :;:•.**:':•:•:i mm mm mm ill V.V.V.'. 24°~ hig I Northern Jcrntory showing latitude^ isohyels and major centres, CLIMATIC CHANGE AND ITS IMPLICATIONS FOR THE AMPHIBIAN FAUNA 55 30- Tyler & Davies (1986) there is a distinct association between rainfall and the number Off species (Fig. 2) mm within rainfall zones where there is 100-500 per mm annum. At rainfalls higher than 500 the trend is 25* notapparent, butthegeographicarea involves Arnhem Landwhich hasbeen largely inaccessibletocollectors. I anticipate that the totals for the more northern latitudes will increase when zoological exploration 20 becomes possible. Because oftheirdependence upon having access to sourcesofmoisture, theevolutionary capacity ofbody 15- size and mass of frogs are closely linked to the reliability ofsources ofmoisture. Species ofsmall size have a surface area to mass relationship that is fitted to reliablesourcesofmoisture. Conversely thecapacity towithstand xeric conditions requiresthatthe surface area from which water is lost is, by some means, reduced. Effectively large, bulky frogs are best equipped for xeric conditions. h- Although the length of the body bears no fixed relationship tobody mass, it is the standardexpression = of size (S-V snout to vent length), In Australian 1J200 10100 AX1> 6010 50[Q 40'0 3010 2010— 100 asplewcaiyess tshmearleleirs mtahraknedfesmeaxlueasl d(eixmcoerppthifosrmt:hemaelaesstearrne RflMfill (mm) Australian species Adehtus brevis). To examine any Fig. 2 Numberofspeciesplottedagainstisohyets{r — .750) geographic trends in size I have used a median n=5* T 40 42 44 48 50 Mean of Medians (S-V) Figo.fJm,edNiuamnbseorfosnfosuptectoievsenotccluenrgrtihng(Sw-iVt)h.iTnwpoarltiinceualrarrelgarteistsuidoensl(ibnoesunhdaavreiebseeantpsliontgtleed:deognreebeeptowseietnion1s2)°palnodtt2e0d°aSga(rin=st.m9e48a)n. Ihe second between 12° and 26°S (r = .975). 5n M I IYI.11R measurement, bcmg ihe midpoint betweenthe-Weof iransportatum of species from southern Queensland the smallest udull male and largest adult lemale, The i"Tyler mi): Fig. 3). first of tllcse analyses followed ihe standard 1° The River Murray presents a further dimension latitudinal divisions (Fig. 3). The second involved because it constitutes a route for the introduction of similar latitudinal divisions but separated at the species from the cast, litoriu pmmi and Criuiu intermediate O..S° divisions (Fig, 4). Essentially the parin\i\>nifera enter the State b> this means, and are results dre similar small species are associated with confined to its vicinity. high levelsol moisture, and inaridareas largerspecies The toadlet Psnidophrync ovadvnutlh has an predominate. extensive disiribulion in Western Australia, whereas in South Australia it has been found only at Victory Well in the Evcruxd Ranges in the northwest. The existence ot species within such restricted areas is ol significancetopalacoclimatic interpretation. Became ofthe small geographic area to which it is confined, 'I- the dependanccofthe species upon moisture, and the '- -• ' existence ofmore arid conditions around the area, it X can be inferred that since the time ofdispersal tothat site, it has not been more arid there than at present. With the exceptionofCnmu ripan'awhich is wholly i vl confined tothe Flinders Ranges, everyspecies in South 1 X Australia has amore extensivedistributionbeyond tin " State boundaries, In fact the percentage ofendcmism m South Australia is less than many other Australian is Stale. 1 '.. .i'r, -.1 saMwy,ft)i'eMfdiiW!* The implications of climatic change I'lii 4, Numberofspeciesoccurring withinparticularlatitudes (boundariesatha](degreepositions)plottedagainstmedian", The climaticvariables that influenceilicgeographic ofsnout to vent length (S-V). Regression line r ?= _S»2t disiribulion ot Australian species of frogs arc x^ry The overall lifestyle offrogs also is reflected along poorly known. Bntftstrom (1^70) was Ihe first In these north-south transects of decreasing available demonstrale anassociation in montanespecies between moisture. In terms ofthe size ofthe individuals there alhtudinal location and tolerance to temperature isashift inthe predominance ofsmall speciestolarpsr fluctuations. In particular he indicated that ihe species onesassociated with rainfall. Equally thereisadi.stincl occupying the cooler habitats had the least capacily change in the overall lifestyle of these same species, to adapt to a change in thermal regime. such that theterrestrial/aquaticmodeshiftsfrommore Unfortunately the climatic variables that have than 50rv in the extreme north of the Nonhern particular influence upon the spatial distribution ot Territory to sew ul 2\° latitude south frogs are, at besl, inferred ralher than demonstrated For example, what is the limiting factor of ihe r.vtviing geographic trends in South Australia distribution of the tree frog Litotiu rulullu which extends as farsouth as Wilpena Creek in the Flinders WithinSouth Australiathere is adinxt .ivsricTutinn Rangev' between the number (and diversity) ot species and This species ranges across the entire northern hall geographic area, but without the latitudinal decrease ol thecotuineni, principally withintheareaofsummer from the and north to the moist south. Instead there rains <Fig. 5). A commensal species, it is clearly are pockets of species, each ol' which has its own capable ofadapting to changing environments Itcan unique features. heassumed thataclimaticchange producing warmer For example any gradient is destroyed by the and moister conditions will enhance the geographic presenceofa wetrefuge likethat ofiheCoongie Lakes range of /,. rubella. system in the northeast ofthis State - an intrusion Perhaps the most significant influence of climatic ofunarea wholly atypical within a broad /.oneot low change will be the creation ol more aquatic breeding and irregular rainfall. The Coongie Lakes Irog fauna sites and the persistence o\' these sites for longer isparticularly rich, but not permanent becauseol the periods. Togetherthesetaetorswill modify habitats in period ol" drought. It has been suggested thai the a manner that is advantageous to frogs. Hence the northeast ofthe Stale presents a dynamic situation in Coongie Lakes are likely to becomemore persistent, which there iscontraction andexpansionul populations and the fauna thete more stable in a temporal sense according |0 theavailability ofmoisture and repeated than at present. CLIMATIC CHANGE AND ITS IMPLICATIONS FOR THE AMPHIBIAN FAUNA 57 A Conclusion 2 , ., Any climatic change that results in a moister and wannerclimate in SouthAustralia islikely toenhance thegeographic distribution oftheconstituent species. This can be assumed because of the wide range of I \yV'^/'/]yI'/%V ••/ x \/\V tspeemcpieersa,tuarnedstehxepefarcitentchaetdaalwraeradmyerbyaSnodumtohiAsutstrreagliimaen ~/V_ > will ameliorate the existing seasonally harsh /{y _ -'A environmental conditions. I Vja rv v -^ / Acknowledgments V^,^^ I would like to express my deep gratitude to the > „ University of Adelaide and the South Australian V^""} Museum, for creating a research environment supportive ofmy studiesofthe South Australian frog faunaoverthepast35 years. Iamalso indebtedtoKelly Fig. 5. Geographic distribution ofLitoria rubella Fennel and Veronica Ward for preparing the figures. References Brattstrom, B. H. (1970)Thermal acclimation in Australian In Tyler, M. J., Twidale, C. R., Davie-s, M. & Wells, C. amphibians. Camp. Biochem. Physiol. 35, 69-103. B. (Eds)"Natural HistoryoftheNorthEastDeserts" (RoyaJ Dukllman, W. E. (1993) Amphibian species ofthe world; Society of South Australia, Adelaide). additions and corrections. Univ. Kansas Mas. Nat. Hist & DAVIES, M. (1986) "Frogs of the Northern Spec Publ. (21), 1-372. Territory". (Conservation Commission of the Northern Tyler. M. J. (1990) Biogcography. Chap. 20. pp. 223-226. Territory, Alice Springs).