Allozyme differentiation in the genus Mantella (Amphibia : Anura : Mantellinae)

Allozyme electrophoresis was carried out on a total of 120 specimens belong ing to 12 species of Malagasy poison frogs of the genus Mantella. Allele fr equencies computed for 17 scored loci were used to analyze intrageneric rel ationships. Genetic distances between Mantella aurantiaca, M. crocea and M, sp. 3 were very low and their specific status is thus questionable. Relati vely low genetic distances were also found between (1) M. betsileo and M, v iridis, (2) M. baroni and M. cowani, and (3) M. pulchra and M madagascarien sis, respectively. M. bernhardi and M. laevigata showed relatively high gen etic distances to all other tars. A phylogenetic analysis of our data large ly confirmed the phenetic clustering; two main lineages could be distinguis hed, one consisting of M, bernhardi, M. expectata, M. viridis and M. betsil eo, and a second one containing the remaining taxa studied. Positioning of M. bernhardi, M laevigata and M. pulchra, however, is problematic as reveal ed by jacknife analysis. Analyses by frequency parsimony revealed that a mo re parsimonious tree topology is achieved by both changing the position of M, bernhardi in the tree, and by placing M. laevigata as a sister species t o all other taxa. The main phylogenetic conclusions drawn from this study a re largely in accordance with other results from independent data sets. The allozyme data show that some very differently coloured taxa are virtually identical genetically, whereas other taxa with nearly identical colour patt erns are genetically well differentiated. The genus may therefore be a good model for studies of aposematism and colour pattern evolution in amphibian s. As a general trend, Mantella species endemic to the rainforests of centr al eastern Madagascar belong to few complexes of closely related forms, whe reas most of the genetically well differentiated species are found in the n orthern part of the island. The differentiation of the main lineages in the genus may thus have largely occurred in northern Madagascar.