Comparative Cytogenetics on Eight Malagasy Mantellinae (Anura, Mantellidae) and a Synthesis of the Karyological Data on the Subfamily

We performed a molecular and cytogenetic analysis on different Mantellinae species and revised the available chromosomal data on this group to provide an updated assessment of its karyological diversity and evolution. Using a fragment of the mitochondrial 16S rRNA, we performed a molecular taxonomic identification of the samples that were used for cytogenetic analyses. A comparative cytogenetic analysis, with Giemsa's staining, Ag-NOR staining and sequential C-banding + Giemsa + CMA + DAPI was performed on eight species: sp. Ca19, (Vences, Glaw, Andreone, Jesu et Schimmenti, 2002), Mantidactylus (Chonomantis) sp. Ca11, M. (Brygoomantis) alutus (Peracca, 1893), M. (Hylobatrachus) cowanii (Boulenger, 1882), Spinomantispropeaglavei "North" (Methuen et Hewitt, 1913), (Glaw et Vences, 1997) and sp. Ca3. , M. (Brygoomantis) alutus and Spinomantispropeaglavei "North" have a karyotype of 2n = 24 chromosomes while the other species show 2n = 26 chromosomes. Among the analysed species we detected differences in the number and position of telocentric elements, location of NOR loci (alternatively on the 6, 7 or 10 pair) and in the distribution of heterochromatin, which shows species-specific patterns. Merging our data with those previously available, we propose a karyotype of 2n = 26 with all biarmed elements and loci of NORs on the 6 chromosome pair as the ancestral state in the whole family Mantellidae. From this putative ancestral condition, a reduction of chromosome number through similar tandem fusions (from 2n = 26 to 2n = 24) occurred independently in Mantidactylus Boulenger, 1895 (subgenus Brygoomantis Dubois, 1992), Dubois, 1992 and Methuen, 1920. Similarly, a relocation of NORs, from the putative primitive configuration on the 6 chromosome, occurred independently in , Dubois, 1992, Dubois, 1992, Boulenger, 1882 and . Chromosome inversions of primitive biarmed elements likely generated a variable number of telocentric elements in Guibé, 1978 and a different number of taxa of (subgenera Glaw et Vences, 2006 and Dubois, 1980) and (subgenera , Glaw et Vences, 1994, Laurent, 1943 and Glaw et Vences, 1994).