Intraspecific phylogeography of Lacerta vivipara and the evolution of viviparity

The lacertid lizard Lacerta vivipara is one of the few squamate species wit h two reproductive modes. We present the intraspecific phylogeny obtained f rom neighbor-joining and maximum-parsimony analyses of the mtDNA cytochrome b sequences for 15 individuals from Slovenian oviparous populations, 34 in dividuals from western oviparous populations of southern France and norther n Spain, 92 specimens from European and Russian viviparous populations, and 3 specimens of the viviparous subspecies L. v. pannonica, The phylogeny in dicates that the evolutionary transition from oviparity to viviparity proba bly occurred once in L. vivipara. The western oviparous group from Spain an d southern France is phylogenetically most closely related to the viviparou s clade, However, the biarmed W chromosome characterizing the western vivip arous populations is an apomorphic character, whereas the uniarmed W chromo some, existing both in the western oviparous populations and in the geograp hically distant eastern viviparous populations, is a plesiomorphic characte r. This suggests an eastern origin of viviparity, Various estimates suggest that the oviparous and viviparous clades of L. vivipara split during the P leistocene. Our results are discussed in the framework of general evolution ary models: the concept of an oviparity-viviparity continuum in squamates, the cold climate model of selection for viviparity in squamates, and the co ntraction-expansion of ranges in the Pleistocene resulting in allopatric di fferentiation. (C) zool Academic Press.