Diversity, elevational variation, and phylogeographic origin of stump-toed frogs (Microhylidae: Cophylinae: Stumpffia) on the Marojejy massif, northern Madagascar

Stump-toed frogs (genus Stumpffia Boettger, 1881) are a diverse group of small-bodied frogs endemic to Madagascar. Seven species of this genus occur on Marojejy, a steep massif in northeastern Madagascar. Here we examine the elevational distribution, phylogenetic position, biogeographic origin, and genetic differentiation of this Stumpffia assemblage. We show that none of these species is another’s closest relative, but rather they are all independent lineages that probably colonised the Marojejy Massif through repeated immigration events. All of the lineages on Marojejy are most closely related to species south and southwest of the massif, except one lineage, formerly known as Stumpffia sp. Ca07, but here assigned to S. sorata as a deep conspecific lineage (and referred to as S. cf. sorata), which occurs also in Sorata, 90 km north of Marojejy. The species on Marojejy are typically restricted to narrow elevational ranges, but at least two species, S. cf. sorata and S. tridactyla, occur over elevations spanning 1000 metres. We assessed the genetic variability of these populations, and found considerable haplotype separation in fragments of the mitochondrial 16S rRNA and nuclear Rag-1 genes, suggesting some disruption of gene flow associated with elevation. We discuss the biogeographic implications of our findings and, based on previously published data, the evolution of non-overlapping bioacoustic parameters among the diverse assemblage of Stumpffia species on the Marojejy massif