Molecular phylogeny of Malagasy poison frogs, genus Mantella (Anura: Mantellidae):: homoplastic evolution of colour pattern in aposematic amphibians

We studied the evolution of colour pattern in Malagasy poison frogs, genus Mantella, a group of diurnal and toxic frogs endemic to Madagascar. Based on a phylogeny reconstructed using 1130 by of the mitochondrial 16S rRNA gene, the genus can be divided into five species groups. Within some of these groups, interspecific genetic divergences were very low (1.2-2.8% sequence divergence) while colour patterns were markedly different. In contrast, Mantella madagascariensis and M. baroni, two species which show extremely similar dorsal coloration patterns, were not included in the same clade. This conclusion was supported by high bootstrap values and by significant rejection of alternative topologies using KH-tests. Analysis of colour patterns and tentative reconstruction of ancestral states yielded five character states shared by these two species but not by their respective sister species, M. aurantiaca and M. nigricans. Considering these detailed similarities as symplesiomorphic therefore requires the assumption of multiple reversals in other species, whereas a homoplastic colour evolution in the sympatric M. madagascariensis and M. baroni appears as most parsimonious. This parallelism may have been triggered by Mullerian mimicry. However, additional data is necessary to support this hypothesis.