This thesis explores geographic patterns of variation in a molecular marker, morphology, and behaviour in two widespread species of Australian myobatrachid frogs, Limnodynastes tasmaniensis and L. peronii. Specifically, I investigate spatial relationships within and among these data sets, and ask three main questions. (1) What role have prominent geographical features such as mountain ranges played in the evolution of open forest anurans in eastern Australia? (2) How do patterns of geographic variation in morphology relate to environmental variation? (3) What does geographic congruence (or lack of it) among behavioural, morphological, and molecular traits suggest about the commonality of evolutionary and ecological forces responsible for intra-specific variation within L. tasmaniensis and L. peronii'?
Based on a new molecular phylogeny, I find that populations of L. tasmaniensis and L. peronii form monophyletic groups within the genus Limnodynastes. However, population genetic structuring within each species is extensive and there appear to be several specific phylogeographic similarities among L. tasmaniensis, L. peronii, and another open forest frog (Litoria fallax). For example, the Burdekin Gap seems to have strongly influenced historical gene flow in all three species. Body size in both L. tasmaniensis and L. peronii was significantly related to latitude and climate variation along the east coast. The relationship between body size and climate was particularly striking in L. peronii, even when the effect of variation in phylogenetic history among populations was accounted for. Moreover, geographic variation in the extent of sexual size dimorphism suggests a possible role for sexual selection in the generation or maintenance of morphological variation among populations. Sexual signals (calls) varied in structure across geography in both species, generally in a manner congruent with major divergences in morphology and mtDNA.
In total, my findings suggest that isolation by distance, climate variation, and some biogeographic barriers may all have had important influence on the evolution of genotypic and phenotypic variation within L. tasmaniensis and L. peronii. Further examination of the role of sexual selection may require determination of the nature of female mating preferences (e.g. based on male calls), the extent of geographic variation in these preferences, and additional information on gene flow and population genetic structuring from nuclear genetic markers. My study highlights the fact that the evolution of widespread non closed-forest anuran taxa along the Australian east coast has occurred in a complex habitat landscape, the recent history of which is far less well understood than that of the region's rainforest systems.