Combining RADseq and contact zone analysis to decipher cryptic diversification in reptiles: insights from Acanthodactylus erythrurus (Reptilia: Lacertidae)

Linnaean and Wallacean shortfalls (Uncertainties on species taxonomy and distribution, respectively) are major factors hampering efficient conservation planning in the current context of biodiversity erosion. These shortfalls concern even widespread and abundant species in relatively well-studied regions such as the Mediterranean biodiversity hotspot which still hosts a large fraction of unrecognised biodiversity, notably in small vertebrates. Species delimitations have long been based on phylogenetic analyses of a small number of standard markers, but accurate lineage identification in this context can be obscured by incomplete lineage sorting, introgression or isolation by distance. Recently, integrative approaches coupling various sets of characters or analyses of contact zones aiming at estimating reproductive isolation (RI) have been advocated instead. Analyses of introgression patterns in contact zone with genomic data represent a powerful way to confirm the existence of independent lineages and estimate the strength of their RI at the same time. The Spiny-footed Lizard Acanthodactylus erythrurus (Schinz, 1833) is widespread in the Iberian Peninsula and the Maghreb and exhibits a large amount of genetic diversity, although the precise number and distribution of its genetic lineages remain poorly understood. We applied a RADseq approach to obtain a genome wide SNPs dataset on a contact zone in central Morocco between the previously described Rif and Middle-Atlas lineages. We show that these two lineages exhibit strong RI across this contact zone, as shown by the limited amount and restricted spatial extant of gene flow. We interpret these results as evidence for species-level divergence of these two lineages. Our study confirms the usefulness of RADseq approaches applied on contact zones for cryptic diversity studies and therefore to resolve Linnaean and Wallacean shortfalls.