Reptiles are known as excellent indicators of the biogeographical history of a given region. This is due to their limited mobility (no long-distance dispersal), effectiveness of ecological barriers, and strong reaction to climate change due to ectothermic metabolism. The same three factors are also effective in isolating populations over a shorter or longer time; thus relict populations may be frequently isolated, and where favorable conditions prevail, they may survive up to the present. Dependent on the isolation time, separate populations develop genetic differences, but particular populations may also retain ancestral character states while other ancestral populations have gone extinct.

The importance of conserving genetic diversity is an internationally accepted goal since the 1992 Rio conference. With this in mind, molecular phylogeographic analyses serve two goals:

1. To reconstruct the evolutionary history of a group of organisms

2. To explore the spatial distribution of genetic diversity with special focus on unique genotypes restricted to particular regional populations; these populations deserve special attention in conservation programs.

A general requirement for a serious phylogeographic study must be that it should cover (ideally) the whole geographic range of a given species complex (Avise 1994).

The results summarized here have been obtained during a large-scale research project to elucidate the phylogeography of eight European reptile species complexes (overviews in Joger et al. 2006, 2007): The European pond turtles (Emys orbicularis complex), the water snakes of the genus Natrix, the European whip snake (Hierophis viridiflavus), the Aesculapian snakes (Zamenis longissimus/Z. lineatus), the adders (Vipera berus complex), the green lizards (Lacerta viridis/L. bilineata), and the sand lizard (L. agilis). These species complexes were selected so that similar phylogeographic patterns can be expected.

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