ZZ/ZW Sex Chromosomes in the Endemic Puerto Rican Leaf-Toed Gecko (Phyllodactylus wirshingi).

Investigating the evolutionary processes influencing the origin, evolution, and turnover of vertebrate sex chromosomes requires the classification of sex chromosome systems in a great diversity of species. Among amniotes, squamates (lizards and snakes) - and gecko lizards in particular - are worthy of additional study. Geckos possess all major vertebrate sex-determining systems, as well as multiple transitions among them, yet we still lack data on the sex-determining systems for the vast majority of species. We here utilize restriction-site associated DNA sequencing (RADseq) to identify the sex chromosome system of the Puerto Rican endemic leaf-toed gecko (Phyllodactylidae: Phyllodactylus wirshingi), in order to confirm a ZZ/ZW sex chromosome system within the genus, as well as to better categorize the diversity within this poorly characterized family. RADseq has proven an effective alternative to cytogenetic methods for determining whether a species has an XX/XY or ZZ/ZW sex chromosome system - particularly in taxa with non-differentiated sex chromosomes - but can also be used to identify which chromosomes in the genome are the sex chromosomes. We here identify a ZZ/ZW sex chromosome system in P. wirshingi. Furthermore, we show that 4 of the female-specific markers contain fragments of genes found on the avian Z and discuss homology with P. wirshingi sex chromosomes.