Abstract
Many ephemeral mudflat species, which rely on a soil seed bank to build up the next generation, are endangered in their natural habitat due to the widespread regulation of rivers. The aim of the present study was to elucidate the role of the soil seed bank and dispersal for the maintenance of genetic diversity in populations of near‐natural river habitats and anthropogenic habitats created by traditional fish farming practices using Cyperus fuscus as a model. Using microsatellite markers, we found no difference in genetic diversity levels between soil seed bank and above‐ground population and only moderate differentiation between the two fractions. One possible interpretation is the difference in short‐term selection during germination under specific conditions (glasshouse versus field) resulting in an ecological filtering of genotypes out of the reservoir in the soil. River populations harbored significantly more genetic diversity than populations from the anthropogenic pond types. We suggest that altered levels and patterns of dispersal together with stronger selection pressures and historical bottlenecks in anthropogenic habitats are responsible for the observed reduction in genetic diversity. Dispersal is also supposed to largely prohibit genetic structure across Europe, although there is a gradient in private allelic richness from southern Europe (high values) to northern, especially north‐western, Europe (low values), which probably relates to postglacial expansion out of southern and/or eastern refugia.
Highlights
The spatial separation of populations influencing rates of gene flow among populations was already a key element in early concepts and models of population ecology and genetics (Wright, 1931, 1943)
The aim of the present study was to elucidate the role of the soil seed bank and dispersal for the maintenance of genetic diversity in populations of nearnatural river habitats and anthropogenic habitats created by traditional fish farming practices using Cyperus fuscus as a model
We found no difference in genetic diversity levels between soil seed bank and above-ground population and only moderate differentiation between the two fractions
Summary
The spatial separation of populations influencing rates of gene flow among populations was already a key element in early concepts and models of population ecology and genetics (Wright, 1931, 1943). The evolutionary forces that shape the genetic structure of species may be altered in anthropogenic versus natural habitats, which may provide opportunities for adaptive niche shifts (Kamdem et al, 2012). Divergent environmental conditions such as the frequency and intensity of flooding during plant growth are expected to exert divergent selection pressures in river and anthropogenic wetland habitats, which may lead to phenotypic differentiation (Böckelmann, Tremetsberger, Šumberová, Grausgruber, & Bernhardt, 2017). We would expect river and anthropogenic populations to differ, because they are exposed to different habitat conditions, which in turn influence determining factors of within-populational variation such as dispersal, drift, and selection. If current and/or previous environmental conditions better supported the survival of Cyperus fuscus in some regions, we would expect higher levels of variation in these regions
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