Chromosome data for Malagasy poison frogs (Amphibia: Ranidae: Mantella) and their bearing on taxonomy and phylogeny

We compared chromosome morphologies for 11 species of Malagasy poison frogs, genus Mantella, and three outgroup taxa (genus Mantidactylus) using conventional and fluorescence staining techniques. All species studied had a karyotype of 2n=26, with five larger and eight smaller chromosome pairs. The 11th pair was acrocentic in Mantella nigricans represents the first such observation in the genus. The nucleolus organizer region (NOR) was located at secondary constrictions on chromosome pair 2 in all Mantella studied and in Mantidactylus grandisonae (while located on other chromosomes in all other species of Mantidactylus studied so far). Heterochromatin distribution was highly variable among Mantella species; C-bands positively staining with DAPI and CMA3 were observed. The possible structure of these bands, seemingly containing both A+T rich and C+G rich heterochromatin, is discussed. Phylogenetic reconstruction using chromosomal characters provided very little information. Evolution of the characters studied is probably either too fast (heterochromatin arrangement) or too slow (NOR location) to match the main cladogenetic events among Mantella species groups.