Nucleolar organizer position was studied by means of AgNOR technique in 11 species of the Lacerta-complex. NOR position is the same in species within a subgenus, but it is different in different subgenera. This observation supports Arnold's (1973) and Guillaume and Lanza's (1982) suggestion that the different subgenera of Lacerta (Gallotia, Lacerta part I, Lacerta part II and Podarcir) are distinct genera. The results of this study also support the hypothesis that the evolution of lacertid karyotypes is characterized by progressive translocation of microchromosomes to macrochromosomes.
Cytological and molecular evidence is provided to characterize the sex chromosomes of several species of Lacertidae. Observations on pachytene and lampbrush stages show that sex chromosomes have different condensation cycles and are only partially paired during meiosis. Bkm probe hybridization to Pst I-treated genomic DNA of Podarcis sicula and Lacerta vivipara shows the same pattern both in males and females. In situ hybridization of the same probe to Lacerta vivipara chromosomes shows no preferential localization of this DNA sequence. The results obtained clearly exclude the possible involvement of Bkm in sex-chromosome differentiation in the species investigated.
Sex chromosomes were studied in eight species of lacertid lizards using C-banding, G-banding and restriction enzyme treatment. All of the species showed female heterogamety. The W chromosome was a microchromosome in Lacerta graeca and Ophisops elegans. Two types of W were found in Lacerta vivipara; in specimens from The Netherlands it was metacentric, whereas in specimens from Russia it was acrocentric or subtelocentric. The W chromosome was homomorphic or nearly homomorphic but completely C-banded and heterochromatic in Lacerta agilis, Podarcis hispanica, Algyroides moreoticus and A. nigropunctatus. In was only possible to find sex chromosomes using the G-banding method in Podarcis sicula. The results obtained, together with data in the literature, suggest that sex chromosomes are likely to be present in all Lacertidae and that their differentiation took place repeatedly and independently in different taxa within the family. A model for sex chromosome evolution in the family, in which the starting point was the heterochromatization of the W chromosome, is proposed.