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 conve ntional and fluorescence staining techniques. All species studied had a kar yotype of 2n=26, with five larger and eight smaller chromosome pairs. The 1 1th pair was acrocentic in Mantella nigricans represents the first such obs ervation 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 D API and CMA3 were observed. The possible structure of these bands, seemingl y containing both A+T rich and C+G rich heterochromatin, is discussed. Phyl ogenetic reconstruction using chromosomal characters provided very little i nformation. 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.