The structure of morphometric and allozyme variation in relict populations of Gypsophila fastigiata (Caryophyllaceae) in Sweden

Patterns of variation and the structuring of diversity in seed phenotype and allozymes were investigated in Sweden Gypsophila fastigiata, a perennial herb with a disjunct ‘Late Glacial relict’ distribution in eastern and northern Europe. The overall patterns of variation in allozymes and seed morphology are congruent and are significantly correlated with geographic distance. However, most of the congruence between the distance matrices based on allozymes and seed morphology is attributable to regional differentiation between the isolated Öland and Dalarna metapopulations. On a local scale, within the two metapopulations, seed shape variation is partially correlated with geography whereas allozyme variation is unrelated to the geographic disposition of the sampling sites. Despite the fact that regional metapopulations can be discriminated on the basis of seed shape and allozyme frequencies, relatively little of the total diversity in seed morphology and allozymes is due to differentiation between regions. Partitioning of diversity into its within- and among-regional, site and individual components, showed that the majority of diversity (52% for seed shape and 91% for allozymes) is stored within sites. Seventy-three percent of the variation in allozymes is due to variation within individuals (i.e. heterozygosity) whereas phenotypic variation in seed shape within individuals is low (0.4% of the total diversity). The events that led to the large scale disjunction of the Late Glacial distribution of G. fastigiata may have shaped the pattern of differentiation observed among the regional isolates of the species. However, the species' history of local population disjunction during post-glacial and historic times has not had a substantial impact on the spatial organization of allozyme and morphometric diversity within regions. Extensive local gene flow may have allowed the regional metapopulations to have functioned as extended effective populations–on a time scale of tens or hundreds of years–and may have hindered the loss of within-site diversity.