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Keywords:

  • Carex digitata;
  • allozymes;
  • geographical variation;
  • phylogeography;
  • glacial refugia;
  • post-glacial migration

Aim

To investigate the distribution, and broad-scale geographical patterns, of variation, in the widespread boreo-nemoral woodland herb Carex digitata throughout its native European range. To interpret the revealed geographical pattern of variation in terms of glacial survival, post-glacial migration and inter-regional gene-flow.

Location

The whole of Europe divided into twenty-five geographical regions.

Methods

Genetic variation at nine polymorphic allozyme loci was analysed in 10–25 individuals from 66 populations from throughout the European range of C. digitata. Allele frequencies were calculated both at the level of populations and at the level of geographical regions, and these frequencies were used to calculate the Cavalli-Sforza chord distance (CSCD). CSCD between neighbouring regions were presented on geographical maps. CSCD at both the population and the regional level were subjected to UPGMA cluster analysis. Standard measures of genetic diversity were calculated and divided into within population, region and species components.

Results

Most alleles had a scattered distribution throughout, but several alleles were mainly found in Fennoscandia and regional allelic richness was the highest here. Cluster analysis on the level of populations did not recover any geographical structure. However, genetic distances between regions, each consisting of 1–4 populations, revealed a clear geographical pattern. Genetic distances were low between (1) Scandinavian and British regions and (2) between Mediterranean regions, moderate between Central European regions and high between far-east European and Caucasian regions.

Main conclusions

A post-glacial scenario involving independent glacial survivals in south-eastern European Russia, the Caucasian Mountains, the Mediterranean area and central Europe is proposed. Northern Europe (i.e. Fennoscandia) appears to have been colonized through many independent long-distance dispersals from different extra-Fennoscandian populations. High regional population densities in Fennoscandia are assumed to have facilitated accumulation of genetic variation and inter-regional gene-flow as compared with more southern populations which are generally of restricted size and appear to have been mutually isolated and subjected to strong genetic drift.