Population genomics and sexual signals identify reproductive interference in Uperoleia

When closely related species come into contact via range expansion, both may experience reduced fitness as a result of the interaction. Selection is expected to favor traits that minimize costly interspecies reproductive interactions (such as mismating) via a phenomenon called reproductive character displacement (RCD). Research on RCD frequently assumes secondary contact between species, but the geographic history of species interactions is often unknown. Landscape genomic data allows tests of geographic hypotheses about species origins and secondary contact through range expansion. We used landscape genomic data from single nucleotide polymorphisms (SNPs), mitochondrial sequence data, advertisement call data, and morphological data to investigate a species complex of toadlets (Uperoleia borealis, U. crassa, U. inundata) from northern Australia. Although the three species of frogs were morphologically indistinguishable in our analysis, we determined that U. crassa and U. inundata form a...