Syntopy of two species of rock lizards (Darevskia raddei and Darevskia portschinskii) may not lead to hybridization between them

Abstract

The two species of rock lizards, Darevsia raddei and Darevskia portschinskii, belong to two different phylogenetic clades of the same genus. They are supposed ancestors for the hybrid parthenogenetic, Darevskia rostombekowi. The present study aims to identify morphological features of these two species and the potential gene introgression between them in the area of sympatry. External morphological features provided the evidence of specific morphology in D. raddei and D. portschinskii: the species differed in scalation and ventral coloration pattern, however, they had some proportional similarities within both sexes of the two species. Males of both species had relatively larger heads and shorter bodies than females. Males of D. raddei were slightly larger than males of D. portschinskii and had longer hindlimbs. Microsatellite genotyping revealed no traces of hybridization or gene flow among these species. We suggest that the absence of individuals with combined morphological and genetic features of the studied species reflects existing reproductive barriers. The hybridization between two bisexual rock lizard species from distant clades is rare and only takes place under very specific environmental conditions.