Recurrent Variation in the Active NOR Sites in the Monkey Frogs of the Genus Cope, 1866 (Phyllomedusidae, Anura)

Treefrogs of the genus Cope, 1866 exhibit expressive chromosomal homogeneity which contrasts with a high variation frequency of the nucleolus organizer region (NOR) related to the group. Currently, the genus contains eleven species and no chromosomal data are available on Peters, 1873, Lutz, 1966 and Miranda-Ribeiro, 1926. Here, we describe the karyotypes of these three species based on Giemsa staining, C-banding, silver impregnation and in situ hybridization (FISH). We were also analyze the evolutionary dynamic of the NOR-bearing chromosome in species of genus under a phylogenetic view. The results indicate that , , and have similar karyotypes, which are typical of the genus . In the NOR was detected in the pericentromeric region of pair 9p whereas in and we report cases of the multiple NOR sites in karyotypes. In the NOR was detected in the pericentromeric region of pair 9p in both homologues and additional sites was detected in pairs 3q, 4p, and 8q, all confirmed by FISH experiments. Already in the NOR sites were detected in pericentromeric region homologues of pair 8q and additionally in one chromosome of pair 13q. A comparative overview of all the karyotypes analyzed up to now indicates the recurrence of the NOR-bearing chromosome pairs and the position of the NORs sites on these chromosomes. We hypothesized that this feature is a result of a polymorphic condition present in the common ancestor of . In such case, the lineages derived from polymorphic ancestor have reached fixation independently after divergence of lineages, resulting in a high level of homoplasy observed in this marker. Our findings help to fill the gaps in the understanding of the karyotype of the genus and reinforce the role of the evolutionary dynamics of the rDNA genes in karyotype diversification in this group.