Chromosome evolution in Cophomantini (Amphibia, Anura, Hylinae)

The hylid tribe Cophomantini is a diverse clade of Neotropical treefrogs composed of the genera Aplastodiscus , Boana , Bokermannohyla , Hyloscirtus , and Myersiohyla . The phylogenetic relationships of Cophomantini have been comprehensively reviewed in the literature, providing a suitable framework for the study of chromosome evolution. Employing different banding techniques, we studied the chromosomes of 25 species of Boana and 3 of Hyloscirtus ; thus providing, for the first time, data for Hyloscirtus and for 15 species of Boana . Most species showed karyotypes with 2n = 2x = 24 chromosomes; some species of the B . albopunctata group have 2n = 2x = 22, and H . alytolylax has 2n = 2x = 20. Karyotypes are all bi-armed in most species presented, with the exception of H . larinopygion (FN = 46) and H . alytolylax (FN = 38), with karyotypes that have a single pair of small telocentric chromosomes. In most species of Boana , NORs are observed in a single pair of chromosomes, mostly in the small chromosomes, although in some species of the B . albopunctata , B . pulchella , and B . semilineata groups, this marker occurs on the larger pairs 8, 1, and 7, respectively. In Hyloscirtus , NOR position differs in the three studied species: H . alytolylax (4p), H . palmeri (4q), and H . larinopygion (1p). Heterochromatin is a variable marker that could provide valuable evidence, but it would be necesserary to understand the molecular composition of the C-bands that are observed in different species in order to test its putative homology. In H . alytolylax , a centromeric DAPI+ band was observed on one homologue of chromosome pair 2. The band was present in males but absent in females, providing evidence for an XX/XY sex determining system in this species. We review and discuss the importance of the different chromosome markers (NOR position, C-bands, and DAPI/CMA 3 patterns) for their impact on the taxonomy and karyotype evolution in Cophomantini.