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

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.