Redefining species boundaries for acoustically and morphologically distinct species of swamp breeding frilled tree frogs (Kurixalus appendiculatus) in the Southwestern Philippines

Abstract

Combining analysis of male advertisement calls, multivariate analysis of continuous morphological variation, biogeographic information, and a multilocus phylogenetic estimate of relationships, we reconsider species boundaries within Philippine populations of the frilled tree frogs Kurixalus appendiculatus. Within the archipelago, the species spans several recognized biogeographic boundaries, with highly divergent genetic lineages isolated within formally recognized, geologically defined, faunal subregions. Given this distribution, at least four possible taxonomic arrangements are possible, varying from one to four possible evolutionary species. Simultaneous consideration of fixed external phenotypic character differences, continuously varying morphometric data, evolutionary relationships, biogeography, and statistically significant differences in mating calls converges on a solution of two Philippine species. We advocate for more widespread, regular, and deliberate sampling of acoustic data to diminish challenges for future studies, where we anticipate the validation of other likely taxonomic arrangements by differences in advertisement calls.