Comparative cytogenetics of four Phelsuma species: insights into chromosome evolution in Malagasy Gekkonidae

Karyotype diversification and chromosome mutations (or macromutations) such as inversions, fusions, and fissions represent understudied factors of biological evolution. We present in this study one of the first experimental cytogenetic analyses on the Malagasy day geckos of the genus Phelsuma. A molecular analysis was performed using a trait of the mitochondrial 12S and a comparative chromosome study with traditional Giemsa coloration, Ag-NOR staining and sequential C-banding (C-banding + Giemsa + fluorochromes) on nine individuals of Phelsuma from different localities. The molecular analysis allowed unambiguous identification of three species (P. lineata, P. laticauda, and P. standingi), while two additional samples likely belong to a still formally undescribed lineage, here named Phelsuma cf. flavigularis. The comparative cytogenetic analysis showed that three of the studied species (P. lineata, P. laticauda and P. cf. flavigularis) have a karyotype composed of 2n = 36 with all acrocentric chromosomes gradually decreasing in length. In turn, P. standingi showed a karyotype of 2n = 32 with two large metacentric pairs (probably originated from two chromosome fusions) and fourteen acrocentric pairs. NOR loci were alternately localized in the study samples on the first (in P. laticauda), the third (in P. standingi), and the 15th chromosome pair (in P. lineata). Sequential C-banding indicated a scarce amount of heterochromatin in all species analyzed, mostly on the centromeric, pericentromeric and telomeric regions of most chromosome pairs. Adding this new data to those available from the literature, we show that common evolutionary trends characterize several clades of the Malagasy Gekkoninae.