Phylogeography, hybrid zones and contemporary species boundaries in the south-eastern Australian smooth frogs (Anura: Myobatrachidae: Geocrinia)

Abstract

Paleo-climatic fluctuations have driven episodic changes in species distributions, providing opportunities for populations to diverge in isolation and hybridise following secondary contact. Studies of phylogeographic diversity and patterns of gene flow across hybrid zones can provide insight into contemporary species boundaries and help to inform taxonomic and conservation inferences. Here we explore geographic diversity within the acoustically divergent yet morphologically conserved south-eastern Australian smooth frog complex and assess gene flow across a narrow hybrid zone using mitochondrial nucleotide sequences and nuclear genome-wide single nucleotide polymorphisms. Our analyses reveal the presence of an evolutionarily distinct taxon restricted to the Otway Plains and Ranges, Victoria, which forms a narrow (9–30 km wide), spatiotemporally stable (>50 years) hybrid zone with Geocrinia laevis, which we describe herein as a new species.