Genetic diversity and population structure of the endangered insect species Carabus variolosus in its western distribution range: Implications for conservation

Abstract

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.

Linking Genetics and Ecology: Reconstructing the History of Relict Populations of an Endangered Semi-Aquatic Beetle

“…Strongly separated were two populations from Southern Slovenia (sites 11 and 12) which showed deviating allele frequencies and some private alleles compared to the other investigated populations. This is confirmed by Bayesian structure analysis (STRUCTURE, Pritchard et al 2000) which generally assigns the individuals of these two populations to one distinct genetic cluster if no a priori assumptions of geographical origin are made (Matern et al 2009). This pattern may be caused by genetic drift and an efficient present isolation between the Southern Slovenian samples and the remaining Central European populations that might have existed since the survival of these populations in different glacial refugia (cf.…”

“…Gersdorf and Kuntze 1957;Perraudin 1960;Morati and Huet 1995). While the investigated populations do not appear to be inbred, they are genetically impoverished in comparison with other carabid beetles (Matern et al 2009). This renders them highly susceptible to genetic stochasticity that is associated with extinction vortices, in particular in the face of expected climatic changes.…”

“…A total of 308 specimens were included in the analysis for a mean sample size of 25 individuals and 16 allozyme loci (Matern et al 2009;Fig. 2).…”

“…We did not observe a directional loss of alleles according to the allele elimination hypothesis (Reinig 1938;Hewitt 1999) nor any regionally specific sets of allozymes and their combination in intermediate populations, which could suggest potential contact zones. The largely random geographic structure of allozyme variants, the lack of private alleles, and the lack of correlation in allele frequencies with geographic distance (Matern et al 2009) suggests that the variation in Central European populations was more similar at first, but that populations lost variability subsequently due to stochastic processes. Hence, the case of C. variolosus could represent an example where postglacial colonization, in combination with subsequent geographic isolation, produced genetic differentiation of a similar magnitude as that resulting from survival in different glacial refuges.…”

Gel and staining recipes and electrophoresis conditions used in this study

“…However, this value lies within the range of "normal" intraspecific variability in habitat specialists of the genus Carabus (cf. Matern et al 2009). …”