Analysis of the chromosomal evolution of the Physalaemus gracilis species group (Anura, Leptodactylidae)

Abstract

The species group Physalaemus gracilis is a clade composed of six species: P. lisei, P. gracilis, P. evangelistai, P. carrizorum, P. jordanensis and P. barrioi. Cytogenetic data on this group are still scarce in the literature, being limited to the description of the karyotypes of P. barrioi, P. gracilis, P. lisei and P. carrizorum, and the chromosome mapping of the PcP190 satDNA in these last three species. Clusters of PcP190 satDNA are found in the (peri)centromeric region associated with heterochromatin on chromosome pairs 2 and 9 in P. gracilis, pair 7 in P. lisei and pair 3 in P. carrizorum. The nucleolus organizer region (NOR) is located on a small chromosome, identified as 8 or 10, being terminal in P. barrioi and P. gracilis, interstitial in P. lisei and pericentromeric in P. carrizorum. The scarcity of cytogenetic markers makes it difficult to ascertain whether these NOR-bearing chromosomes are homeologous and prevents further interspecific comparisons. In the present project, we want to provide new chromosomal information about the Physalaemus gracilis group of species, in order to deepen the knowledge about the already described karyotypes and to better understand how the karyotypic evolution occurred in this group. Thus, our objectives are: 1) to describe the karyotype of Physalaemus evangelistai based on Giemsa-stained, C-banded and silver-stained metaphases; 2) to map the DNAsat PcP190 and the gene for snRNA U2 in the karyotypes of some species of the group using FISH; 3) to analyze the obtained data together with previously published data cytogenetic in the light of phylogenetic inferences already available for the group.