Phylogeographic pattern and taxonomic revision of the Kaloula baleata species complex (Amphibia, Anura, Microhylidae) with description of two new species from Indochina

Abstract

Despite increased attention by molecular taxonomists, the herpetofauna of Southeast Asia still hides many undescribed species among far-ranging taxa. In this study, we re-examine the mitochondrial diversity of painted frogs of the microhylid genus Kaloula, based on ~2,455 bp of published and new 12S and 16S rRNA sequences, and describe two new species from the tropical forests of southern Vietnam and central Laos based on integrative evidence. These species, which belong to the K. baleata complex, feature species-level mitochondrial divergence (> 4.4% at 16S rRNA) and are both morphologically well-differentiated from each other and from the recently described K. indochinensis, to which they were previously confounded. Comparative examinations also indicate distinct male advertisement calls and unique coloration features. Based on genetic barcoding, we preliminarily revise the species distribution ranges in the K. baleata complex, which support a general pattern of biogeographic partitioning that has been widely retrieved among the Indochinese amphibians studied so far. Molecular diversity within K. baleata further suggests genetic structure across Sundaland, namely three shallow mitochondrial haplogroups worthy of fine-scale phylogeographic and taxonomic investigations. Furthermore, our study highlights the propensity of amphibian species “hidden in plain sight,” even among recently studied taxa, thus calling for caution when specifying type specimens—the type series of K. indochinensis, described in 2013, includes specimens of the one of the new species. Our study emphasizes the continued need for thorough herpetological surveys even in supposedly well-known parts of Indochina and sets the ground for future research in Kaloula painted frogs, notably to test evolutionary and taxonomic hypotheses with genomic loci.