Molecular and bioacoustic divergence in Mantidactylus granulatus and M. zavona n.sp. (Anura: Mantellidae): bearings for the biogeography of northern Madagascar

Abstract

We analysed the genetic and bioacoustic variability in Mantidactylus granulatus, a semi arboreal frog species endemic to the northern portion of Madagascar. Advertisement calls had a longer note duration in northeastern as compared to northwestern populations. Specimens from mid altitudes in the Tsaratanana Massif (Northern Central Region) showed distinct call differences. They also had a high sequence differentiation in a fragment of the mitochondrial 16S rRNA gene (pairwise divergence 8.6 %), while all other populations were genetically rather uniform. This Tsaratanana population is described as the new species Mantidactylus zavona; it is also morphologically distinct from the sympatric M. granulatus in that it has a smaller body and a shorter, wider head. The relatively small differences between M. granulatus from different sites in northern Madagascar (pairwise 16S divergences up to 1.4 %), including the isolated Montagne d’Ambre, supports a biogeographic scenario in which the lowland rainforests in this area were connected in Pliocene Pleistocene times. By contrast, the presence of endemic species at higher altitudes of the Tsaratanana Massif may be seen as evidence for a longer isolation of the habitats at these elevational levels.