Finding Vipera pontica: morphological evidence of a possible hybrid between V. kaznakovi Nikolsky, 1909 and V. ammodytes transcaucasiana Boulenger, 1913 from central Georgia

Abstract

Vipera pontica was originally described from two juvenile specimens from northeastern Turkey and has long been considered taxonomically enigmatic. Recent genomic studies suggest that these snakes represent a sporadic hybrid between V. kaznakovi and V. ammodytes transcaucasiana. We here report on an adult viper with an intermediate phenotype, part V. kaznakovi and part V. ammodytes transcaucasiana, observed in the Kura Valley of central Georgia within a known contact zone between the two other taxa. This snake combined diagnostic traits of both V. kaznakovi and V. ammodytes transcaucasiana, including an upturned but hornless snout, fragmented head scalation, intermediate ventral and subcaudal counts, a mixed dorsal zigzag pattern, and a bicoloured tail tip. This observation is the first documented adult resembling V. pontica and the first such record from Georgia, extending the known occurrence of this putative hybrid form approximately 150 km to the east of the type locality. Our findings support the interpretation of V. pontica as a rare hybrid arising in narrow parapatric overlap zones rather than a distinct evolutionary lineage, and this taxon therefore belongs in the synonymy of both V. kaznakovi and V. ammodytes transcaucasiana.