Call Evolution in Neobatrachus (Anura: Myobatrachidae): Speculations on Tetraploid Origins

Four species of the Australian burrowing frog Neobatrachus are tetraploid and another six are diploid. The origins of the tetraploids are unknown. I describe advertisement calls of all 10 species and compare those of diploids and tetraploids. Calls of diploids can all be easily distinguished. All four tetraploids have calls with low pulse numbers and low pulse rates: broadly similar to calls of the diploid N. fulvus. The calls of N. kunapalari differ in three properties from those of the other three tetraploid species, N. aquilonius, N. centralis, and N. sudelli. I examined four models to account for call evolution in this genus. Calls of tetraploids may be unaltered from those of their diploid parents, have a forced change imposed by cell characteristics associated with doubling of the chromosome set, have evolved from an interaction (reproductive character displacement) with diploid parents, or have a hybrid structure derived from an allotetraploid origin. Under each model, I offer predictions of relationships of Neobatrachus species that must be further tested with an adequate phylogenetic analysis based on independent characters.