Taxonomic inflation and a reconsideration of speciation in the Andes: the case of the high-elevation tree frog Dendropsophus molitor (Anura: Hylidae)

Abstract

Dendropsophus molitor is a hylid frog endemic to the Eastern Cordillera of the Colombian Andes, where it exhibits extensive geographic variation in size and colour pattern. Previous multivariate analyses of acoustic and genetic data suggested that northern and southern populations of D. molitor were distinct lineages, and consequently, the northern populations were described as Dendropsophus luddeckei. In this study, we conducted morphometric and genetic analyses of populations of D. molitor and D. luddeckei to test the validity of this recent taxonomic split. We sequenced the mitochondrial genes 12S, 16S, and COI, and the nuclear marker POMC, and also tested whether variation in the MC1R gene was associated with colour polymorphism in these frogs. Phylogenetic analyses recovered D. molitor and D. luddeckei as polyphyletic and species delimitation tests failed to recover them as separate lineages. Genetic differentiation between populations was mostly explained by high intra- and interpopulation variation in the absence of a north-south split, and we found no differences in morphometry between northern and southern populations. In addition, the coding region of MC1R is not associated with colour polymorphism. Thus, multiple lines of evidence suggest that D. luddeckei is not a valid species and D. molitor should be considered a single species. Our study highlights the danger of taxonomic inflation in the face of limited geographic sampling and a lack of clear diagnostic characters.