Progressive differentiation of the W sex‐chromosome between oviparous and viviparous populations ofZootoca vivipara(Reptilia, Lacertidae)

Abstract

Populations of Zootoca vivipara appear karyologically well differentiated by heterochromatin distribution both in autosomes and sex-chromosomes; allopatric oviparous populations possess few elements with centromeric heterochromatin and W acrocentric sex-chromosomes with heterochromatin only on the centromere; Alpine, as well as central-western European viviparous populations possess conspicuous centromeric bands of heterochromatin on all of the chromosome pairs and a metacentric W chromosome with paracentromeric and telomeric heterochromatin bands; viviparous populations, living east and possibly north of the Carpathian Mountains, have many elements with interstitial and telomeric heterochromatin and an acrocentric W chromosome with telomeric and subtelomeric heterochroma. These data suggest an origin and evolution of sex-chromosomes in this species, that, interestingly, parallels the recent hypothesis (Heulin et al., 1993) on the rise and evolution of viviparity and speciation in Zootoca.

Intraspecific Phylogeography of Lacerta vivipara and the Evolution of Viviparity

“…Moreover, the time scale of this scenario is in accord with our allozymes and mtDNA analyses which both suggest that the differentiation of the two reproductive forms of L. vivipara could have begun between 2 and 0.5 mybp, that is, during the Pleistocene (Guillaume et al, 1997;Heulin et al, 1999). Finally, some aspects of this scenario are also consistent with a karyological variation identified in L. vivipara: females from southwestern oviparous populations and from eastern viviparous populations both have an uniarmed (acrocentric-subtelocentric) W chromosome, whereas those from western viviparous populations possess a biarmed (metacentric) W chromosome (Odierna et al, 1998; and Fig. 1).…”

“…It has long been stressed that a particular karyological event occurred in L. vivipara: an unequal number of chromosomes in males and females (respectively 2N ϭ 36 and 35 chromosomes), which has been documented for the viviparous populations and for the western oviparous populations of this species, has been interpreted as the result of a fusion of an ancestral W chromosome with an autosome, giving rise to a neo-W and to a particular female sex chromosome system called Z1Z2W (Chevalier et al, 1979;Odierna et al, 1993Odierna et al, , 1998Belcheva et al, 1986;Kupriyanova et al, 1995;Kupriyanova and Rudi, 1990;Kupriyanova 1986Kupriyanova , 1990Kupriyanova and Böhme, 1997). However, the evolutionary stage just prior to the W ϩ autosome fusion, (i.e., females with 2N ϭ 36 chromosomes) had not been discovered until very recently.…”

“…Sequencing of double-stranded DNA was performed in both directions using a Big Dye terminator cycle sequencing kit (Perkin-Elmer Biosystems) using the manufacturer's instructions and sequences were run on an ABI 310 genetic analyzer (Perkin-Elmer Biosystems). Sequence were aligned using Sequencher and phylogenetic analyses were performed with PAUP* version 4.0b4 (Swofford, 1999) using maximum-parsimony (MP, heuristic search and 100 random addition of sequences) and neighbor-joining (NJ Kupriyanova, 1990;Odierna et al, 1998) between the western viviparous group with a biarmed W chromosome, the eastern viviparous group with an uniarmed W chromosome, and the subspecies L. v. pannonica which also possess a uniarmed W. with Juke and Cantor distances) methods. Statistical support of nodes was estimated by bootstrapping (1000 replicates).…”

Isolation and Characterization of Interspersed Repeated Sequences in the Common Lizard, Zootoca vivipara, and Their Conservation in Squamata

“…carniolica , the viviparous Hungarian population of Osca, and Austrian populations of Turracher Höhe and Neunkirchner Hütte. A complex Z 1 Z 1 Z 2 Z 2 /Z 1 Z 2 W system with different W morphologies was found in other populations: a telocentric/subtelocentric W chromosome is present in oviparous Pyrenean populations and viviparous eastern populations, a metacentric W chromosome is detected in central-western European populations, and a submetacentric one is characteristic of Romanian populations [Odierna et al, 1998[Odierna et al, , 2004Kupriyanova et al, 2005 and unpublished data] ( Fig. 1 ).…”

“…material, see www.karger.com/doi/10.1159/000497304 ). All these specimens were already used in other studies [Odierna et al, 1998[Odierna et al, , 2001[Odierna et al, , 2004Kupriyanova et al, 2005;Surget-Groba et al, 2001.…”