Since the 1930s, several European zoologists have developed scenarios for glacial refuges and postglacial expansions, mainly based on studies of the morphological differentiation of populations and distribution patterns of species. For example, Holdhaus described the distribution of blind euedaphic and troglobitic beetles restricted to an area South of a well-defined line crossing the Southern Europe from West to East. In these areas, where many endemic animal and plant species occur, other species that are currently more widely distributed in Europe were probably able to survive the glacial period(s). Molecular analyses of 77 populations of the silvicolous ground beetle Carabus auronitens support the existence of these postulated refuge areas. Genetic differentiation of C. auronitens provides good evidence for multiple refuges, which are, however, situated further North than previously assumed. Furthermore, genetic differentiation is more pronounced in the areas South of the "Holdhaus line" than in the areas North of it.

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Genetic variation was assessed in the endangered species C. variolosus (Coleoptera: Carabidae), which is listed in the European Habitats and Species Directive. Twelve populations from the north-western margin of its range in Germany and France to the border region between Slovenia and Croatia were investigated for variation at 16 allozyme loci. In general, genetic diversity was rather low as indicated by a mean allelic richness of 1.3 alleles per locus, a mean gene diversity (H E ) of 0.071 and a mean proportion of polymorphic loci (P 95% ) of 16%. Genetic diversity did not change directionally from the margin towards the core of the range. Very high differentiation between populations (overall F ST = 0.465), the results of a Mantel test, and poor accordance between geographical and genetic distance suggest a high degree of isolation of the island-like distributed populations. High F ST values and genetic distance measures, even between geographically close populations within the same drainage, confirm a very low dispersal power of this habitat specialist of headwater areas and swamps in woodlands, even in comparison with other flightless beetles. It is concluded that the majority of populations are demographically independent. Hierarchical F-statistics indicate that almost half of the genetic variance is found between regions and populations. Therefore, we recommend that conservation efforts consider every population as a management unit and aim to maintain as many populations as possible over as many regions as possible.

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To counteract habitat fragmentation, the connectivity of a landscape should be enhanced. Corridors are thought to facilitate movement between disconnected patches of habitat, and linear strips of habitat connecting isolated patches are a popular type of corridor. On the other hand, the creation of new corridors can lead to fragmentation of the surrounding habitat. For example, heathland corridors connect patches of heathland and alternatively hedgerows connect patches of woodland. Nevertheless, these corridors themselves also break up previously connected patches of their surrounding habitat and in so doing fragment another type of habitat (heathland corridors fragment woodlands and woodland strips or hedgerows fragment heathlands). To overcome this challenge we propose the use of semi-open habitats (a mixture of heathland and woodland vegetation) as conservation corridors to enable dispersal of both stenotopic heathland and woodland species. We used two semi-open corridors with a mosaic of heathland and woody vegetation to investigate the efficiency of semi-open corridors for species dispersal and to assess whether these corridors might be a suitable approach for nature conservation. We conducted a mark-recapture study on three stenotopic flightless carabid beetles of heathlands and woodlands and took an inventory of all the carabid species in two semi-open corridors. Both methodological approaches showed simultaneous immigration of woodland and heathland species in the semi-open corridor. Detrended correspondence analysis showed a clear separation of the given habitats and affirmed that semi-open corridors are a good strategy for connecting woodlands and heathlands. The best means of creating and preserving semi-open corridors is probably through extensive grazing.