The Common Eurasian Lizard Zootoca vivipara (Jacquin, 1787) from Russia: Sex Chromosomes, Subspeciation, and Colonization

Abstract

Data on the karyotypes and sex chromosomes of the common Eurasian lizard, Zootoca vivipara (Jacquin, 1787) (family Lacertidae), the Kaliningrad Region (Königsberger Gebiet) in the Baltic Sea Basin of Russia are presented. Twenty five viviparous specimens of Zootoca vivipara from five geographically separate localities have been identified on the basis of their karyotypes, and as a result two different chromosomal forms of nominative subspecies Z. v. vivipara have been recognized: 1. viviparous western form — in female 2n = 35 with the W-sex submetacentric macrochromosome (SV) (Z₁Z₂W type); 2. viviparous Russian form — in female 2n = 35, with the W-sex acrocentric/subtelocentric macrochromosome (A/ST) (Z₁Z₂W type). For the present these are marginal populations of the two detected forms of Z. v. vivipara on the southern coast of the Baltic Sea. Their distribution in the Kaliningrad oblast’ has been established and some differences in their biotopic characters have been noted. The morphology of sex chromosomes can be evidently used both to identify specimens as well as to recognize subspecies boundaries in Z. vivipara. To date a mosaic or sympatric distribution of the above forms is not observed in this region, however a parapatric zone is for the first time determined. There is no cytogenetic indication of introgression in specimens from the localities close to their chromosome border. The chromosome rearrangements, in particular in W-sex chromosome, accompany the form-formation, subspeciation and colonization processes in the species. These data suggest a higher taxonomic status of the western and the Russian forms of Z. v. vivipara. Our results support the hypothesis that some region in the Baltic basin may be a zone of secondary contact between two chromosomal forms of the species and indicate that the parapatric zone between them is located in the central part of the Kaliningrad Region. The available chromosome data allow us to assume that during the postglacial time populations of Z. vivipara belonging to the western form of Z. v. vivipara have been colonizing the Kaliningrad Region from the West and the South-West and those corresponding to the Russian form of Z. v. vivipara, from the East and the South-East.