NGS approach for investigating evolutionary transition form oviparity to viviparity in squamate reptiles

Some squamate reptile species provide a unique model system for gaining crucial information about the evolutionary transition from oviparity to viviparity in vertebrates. The lizard Zootoca vivipara is one of the few species with distinct reproductive modalities in different subspecies; in particular, Z. v. carniolica is an egg-laying lizard while Z. v. vivipara is a live-bearing one; they both live in the Eastern Italian Alps, sometimes in sintopy. This provides an interesting natural setting for studying the evolutionary shift in reproductive mode. Some populations were analysed using classical genetic markers (mitochondrial, nuclear DNA sequences and autosomal microsatellites). The mtDNA results indicated a marked divergence between the two subspecies (around 5% at the cytochrome B), as well as nuclear microsatellites. Possible existence of hybrid individuals in Carnic Alps, as recently reported by morphological evidences, has boosted the interest on this topic. RAD-tag sequencing, a next-generation sequencing technique that allows simultaneously discovering and analyzing hundreds of thousands of SNPs, was then applied to Zootoca vivipara subspecies in order to identify mutations correlated with the reproductive modality and with related adaptive traits.