Table Of ContentTramtutious 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).
