Phylogeography of Ptychadena mascareniensis suggests transoceanic dispersal in a widespread African-Malagasy frog lineage
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.
Document Type: Research Article
Affiliations: 1: Institute for Biodiversity and Ecosystem Dynamics, Zoological Museum, University of Amsterdam, Amsterdam, The Netherlands 2: Institute of Zoology, Department of Ecology, University of Mainz, Saarstrasse, Mainz, Germany 3: Department of Animal Ecology and Tropical Biology, Biocenter, University of Würzburg, Am Hubland, Würzburg, Germany 4: Zoology Department, University of the Western Cape, Bellville, South Africa 5: Zoologische Staatssammlung, Münchhausenstrasse, München, Germany 6: Zoologisches Forschungsinstitut und Museum A. Koenig, Adenauerallee, Bonn, Germany
Publication date: April 1, 2004