Beschreibung:
<p>In the Westphalian Lowlands (NW Germany), the carabid beetle Carabus auronitens inhabits forests and semi-natural (secondary) woods. Southwest of the city of Münster the frequencies of two alleles of an esterase-encoding gene (Est-1) change continuously by about 90% over a distance of 20 km. Within this cline several local populations, that are only a few hundred meters apart, differ significantly, suggesting that the evolution of the cline is a rather recent event. We propose the following hypotheses to explain these observations: (1) C. auronitens survived the period of nearly complete anthropogenic destruction of woodlands (during Middle Ages and early Modern Times) in the region southwest of Münster in a few small isolated populations; (2) in these refugia, the allele frequencies shifted by random drift in opposite direction (neutrality of the esterase genotypes against selection is supposed); (3) after semi-natural woods had regenerated and forests had grown up the refugial populations expanded and fused to a large metapopulation. We suggest that the cline observed in the Est-1 alleles reflects the continuous dynamics of the newly founded metapopulation. It is shown that in C. auronitens both population growth rates and individual dispersal ability seem to be high enough for an expansion over relatively large distances within a relatively short period.</p>