Lacerta viridis has been subdivided into two biological species, Western European L. bilineata Daudin, 1802 and Eastern European L. viridis (Laurenti, 1768). The hybrids between them show reduced fertility (Rykena 1991, 1996, 2001)
Amann et al. (2001) identified a hybrid zone in Northeastern Italy and the adjacent part of Slovenia, in which a restricted and asymmetrical gene flow (predominantly from the East to the West) could be detected (Joger et al. 1998). This type of hybrid zone of "species in statu nascendi" will remain spatially restricted, but may be stable for a long time, if it is stabilized by equivalent invasion and evasion, hybridization, and selection (Barton and Hewitt 1988).
Our cytochrome b tree (Fig. 3) is concordant with a previously published allozyme tree (Amann et al. 1997, Joger et al. 2001) by grouping in two main clusters - the two species L. bilineata and L. viridis. Both trees group the populations from the hybrid zone (Udine, Trieste) to viridis, which contradicts a recent analysis by Böhme et al. (2006). These authors included those populations (and Slovenian populations) in a "Western Balkan group" extending South to Greece. As this group clustered with L. bilineata in their tree, they assigned it to L. bilineata, in order to prevent a paraphyletic viridis. Mayer and Beyerlein (2001), using 12s and 16s RNA genes, also found Western Greek viridis associated with bilineata, while Brückner et al. (2001) found that cytochrome b from the same animals clustered with viridis. These contradictory results were confirmed by Godinho et al. (2005). However none of the teams had included Turkish L. viridis in their analysis. In our tree (Fig. 7), with Turkish lizards included, there is no paraphyly of L. viridis. The lizards from Trieste and Udine cluster with viridis, as well as the Western Balkan group. The Croatian population from the island of Cres clusters with the Western bilineata. This was also found by Brückner et al. (2001) and by Godinho et al. (2005). Cres may harbor a relict population of a once more easterly distributed bilineata, recently restricted by a Western advance of viridis.
For both L. viridis and L. bilineata, a number of subspecies have been described (Nettmann 2001). Most of them are found in Southern Italy (L. bilineata), Greece, or Turkey (L. viridis) and point to multiple glacial refuges in those areas. However, the molecular data are not yet sufficient to decide upon this issue.
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