The Frog Fauna of Southwestern Australia: Diverse, Bizarre, Old, and Polyandrous
My research on anurans has been diverse: biogeography, speciation, acoustics, polyandry, sperm competition, and conservation. My interests in biology started in natural history but, in the late 1960s as an undergraduate student, I was receptive to emerging new ideas in biogeography and evolutionary biology: continental drift and neutral theory. My focus in this “Perspective” is an explanation of how diversity has evolved in the frog fauna of southwestern Australia, where I have worked since 1978. I discuss the roles of range fragmentation, genetic drift, directional sexual selection, polyploidy, and simultaneous polyandry as processes driving the evolution of diversity in the sometimes-bizarre frog fauna of southwestern Australia. I identify features that can characterize polyandrous anurans: e.g., large testes, sperm morphology, and, possibly, complex calls with an example of the latter in Geocrinia leai. I discuss how current anuran life histories vary across rainfall and temperature gradients and how derivation of more-arid adapted forms is a well-defined historic biogeographic pattern in southwestern Australia. My observations over time leave me cautiously optimistic about the prospects for frogs affected by global warming.ABSTRACT
Distribution of Geocrinia leai in southwestern Australia (closed grey circles) (modified from Atlas of Living Australia, 2019). Atlas data were edited to remove records with obvious location errors (e.g., sites that plotted in the ocean). Recording sites are linked to large black circles. The number in each large circle is the percentage of frogs at that site making calls with a single introductory note. Most calls were recorded in 2013, one site in 2007, and one in 2018. Recording dates and sample sizes are given in Table 2. Town names indicate approximate locations: all towns are coastal. Box upper right indicates the portion of Australia covered by the main map, dotted line indicates the approximate position of the 300-mm annual rainfall isohyet: the eastern edge of the area of reliable winter rainfall in south-western Australia.
Oscillographs of calls of Geocrinia leai: complex introductory note—west coast populations (upper trace); and simple introductory note—south and southeast coast populations (lower trace). Exported from Raven Pro 1.5 as screen shots and edited to remove all but the oscillograph trace. Time bar applies to both traces. Calls were recorded at 11.2°C (Jalbarragup—west coast) and 11.1°C (Elleker—south coast), eliminating differences because of temperature. The west coast call has two distinct notes in the introductory component, but the second note is much longer and has distinct amplitude modulation, giving three amplitude peaks. The south coast call has a single introductory note with no internal amplitude modulation. In all areas the number of repeated notes varies between successive calls from individual frogs.
