Phylogeography of Ptychadena mascareniensis suggests transoceanic dispersal in a widespread African‐Malagasy frog lineage

Abstract

Aim The Mascarene ridged frog, Ptychadena mascareniensis, is the only African amphibian species thought to occur on Madagascar and on the Seychelles and also Mascarene islands. We explored its phylogenetic relationships and intraspecific genetic differentiation to contribute to the understanding of transoceanic dispersal in amphibians. Methods Fragments of the mitochondrial 16S rRNA gene were sequenced from specimens collected over most of the distribution area of P. mascareniensis, including populations from Madagascar, Mascarenes and Seychelles. Results We identified five deeply divergent clades having pairwise divergences >5%, which probably all represent cryptic species in a P. mascareniensis complex. One of these seems to be restricted to Madagascar, the Mascarenes and the Seychelles. Sequences obtained from topotypic material (Réunion) were identical to the most widespread haplotype from Madagascar. The single Mauritian/Seychellean haplotype differed by only one mutation from a Malagasy haplotype. Main conclusions It is likely that the Mascarene and Seychellean populations were introduced from Madagascar by humans. In contrast, the absence of the Malagasy haplotypes from Africa and the distinct divergences among Malagasy populations (16 mutations in one divergent hapolotype from northern Madagascar) suggest that Madagascar was populated by Ptychadena before the arrival of humans c. 2000 years ago. Because Madagascar has been separated from Africa since the Jurassic, this colonization must have taken place by overseas rafting, which may be a more widespread dispersal mode in amphibians than commonly thought.

Amphibian phylogeography: a model for understanding historical aspects of species distributions

“…Madagascar is a particularly interesting case. It separated from mainland Africa some 130 million YBP, was occupied by humans as recently as 2000 YBP, and has over 200 species of anurans more than 99% of which are endemic (Vences et al, 2004). However, the Mascarene ridged frog Ptychadena mascarensis is one of only two species found extensively in mainland Africa as well as in Madagascar.…”

“…However, the Mascarene ridged frog Ptychadena mascarensis is one of only two species found extensively in mainland Africa as well as in Madagascar. MtDNA 16S rRNA sequence analysis of 78 specimens collected across the entire biogeographical range generated a fascinating inference (Vences et al, 2004). Madagascar frogs had a range of haplotypes found nowhere on the mainland, and which included two very Amphibian phylogeography I Zeisset and TJC Beebee divergent lineages within the island.…”

Cenozoic biogeography and evolution in direct-developing frogs of Central America (Leptodactylidae: Eleutherodactylus) as inferred from a phylogenetic analysis of nuclear and mitochondrial genes

“…This ''young Craugastor'' hypothesis has a disadvantage in requiring that the ancestral Craugastor rafted to Central America during the late Eocene. Trans-oceanic dispersal by amphibians is an unlikely phenomenon (Darwin, 1859), but it does happen (Hedges et al, 1992;Vences et al, 2003Vences et al, , 2004. One advantage of a younger Craugastor, however, is that the southern portion of its biogeographic history would be more easily reconciled with the relatively young age of lower Central America (Coates et al, 2004;Whitmore and Stewart, 1965).…”

A previously unrecognized radiation of ranid frogs in Southern Africa revealed by nuclear and mitochondrial DNA sequences

“…Despite recent compelling evidence for the ability for transoceanic dispersal in amphibians (Hedges et al, 1992;Vences et al, 2003bVences et al, , 2004, there is little doubt that continental drift has had a major inXuence in shaping their current distribution and phylogeny. The close relationships of the recently discovered Nasikabatrachus from India with Nesomantis from the Seychelles strikingly demonstrated the importance of the Gondwanan breakup for the vicariance biogeography and hence phylogeny of these basal Neobatrachian frogs (Ranoidei sensu Sokol, 1977).…”