Is Vipera orlovi a Distinct Hybrid Species?

Abstract

The species status of Vipera orlovi is discussed in the context of the concept of hybrid speciation. The genome of this Caucasian viper is composed of the genomes of Vipera kaznakovi (major part) and of Vipera renardi (about 20%). V. orlovi is intermediate in ecology between its ‘parental species,’ however its habitat is not the typical habitat of neither V. kaznakovi nor V. renardi. As all three taxa are allopatric, there is no evidence of current geneflow between them. Pleistocene climatic changes may have mediated contact and hybridization between V. kaznakovi and V. renardi. The resulting hybrid flock may have had a wider ecological range than its parental species, enabling a descendant lineage to occupy a novel niche which was previously unoccupied. Similar scenarios of hybrid speciation have probably occurred in vipers throughout the Caucasus. Although the future fate of this hybrid speciation remains open unless full genetic isolation has occurred, we propose to grant species status to Vipera orlovi. This is in line with the genotypic cluster species concept and the unified species concept.