Habitat fragmentation and recent bottlenecks influence genetic diversity and differentiation of the Central European halophyte Suaeda maritima (Chenopodiaceae)

Abstract

Central European salt habitats are mainly restricted to the maritime coast but scattered occurrences can also be found inland. In inland habitats, human activities have caused losses and reductions in the size of natural salt sites but have also created new anthropogenic habitats around potash mining dumps colonized by halophytic species in the last 30 yr. We aimed to investigate the effects of bottlenecks, isolation, and ongoing habitat fragmentation on the genetic variation of a species commonly growing in these special habitats. We used 10 microsatellite markers to compare genetic diversity and differentiation of 31 populations of Suaeda maritima (Chenopodiaceae) from Central European coasts and inland habitats. Two approaches were applied to analyze the tetraploid data based on allele frequencies directly derived from microsatellite data and from transformed binary data. In comparison to the coastal populations from the North Sea and the English Channel, significantly reduced genetic variation and increased between-population differentiation was revealed for populations from the German inland and the Baltic Sea coast. Genetic structure analyses clearly separated coastal and inland populations. Our results indicate that gene flow is restricted among populations from inland salt sites and the Baltic Sea coast, presumably due to their isolation, small sizes, genetic bottlenecks and/or founder events. Patterns of allele distribution indicate some occasional genetic exchange among habitat types in the past. Anthropogenic salt sites may facilitate gene flow among inland salt habitats preventing endangered inland halophyte populations from genetic erosion.