Abstract
ContextLand use change reduced calcareous grasslands throughout Europe during the last decades. Subsequent fragmentation and habitat deterioration led, moreover, to a massive biodiversity decline. To counteract this alarming development, a clear understanding of genetic variation patterns, as fundamental level of biodiversity, becomes inevitable.ObjectivesThe aim of our study was to identify the drivers of genetic variation in common calcareous grassland plant species. More specifically, we tested whether genetic diversity or differentiation of Asperula cynanchica, Campanula rotundifolia, and Linum catharticum depend on habitat age, landscape structure, habitat quality, and/or population size.MethodsWe investigated 912 individuals, 304 per study species, from 19 calcareous grasslands across the Swabian Alb in Baden-Württemberg (Germany) using AFLP analyses.ResultsWe observed no significant influence of habitat age on genetic diversity and differentiation. Habitat quality also had no impact on genetic diversity and population size only showed weak effects. However, genetic diversity strongly depended on landscape structure represented by distance to the nearest settlement, total area of surrounding calcareous grasslands, and their connectivity.ConclusionsMigratory sheep herding is considered as main land use in calcareous grasslands on the Swabian Alb and thus, landscape structures in the study region may describe movement patterns of grazing livestock. In this study, genetic variation in calcareous grassland populations was strongly affected by surrounding landscape structures and subsequent grazing patterns. Therefore, we assume that moderate grazing intensities over the long term may increase levels of genetic diversity, whereas periods of overgrazing or abandonment could lower genetic diversity.
Highlights
IntroductionDewenter and Tscharntke 2002; Karlik and Poschlod 2009; Poschlod 2017)
Central European calcareous grasslands represent local biodiversity hotspots due to their long existence, habitat diversity, and species richness (Steffan-Dewenter and Tscharntke 2002; Karlik and Poschlod 2009; Poschlod 2017)
Migratory sheep herding is considered as main land use in calcareous grasslands on the Swabian Alb and landscape structures in the study region may describe movement patterns of grazing livestock
Summary
Dewenter and Tscharntke 2002; Karlik and Poschlod 2009; Poschlod 2017) They constitute valuable habitats for many specialised, rare, and endangered plant or insect species and are, considered as key areas for biodiversity conservation in agricultural landscapes (Raatikainen et al 2009; Rosengren et al 2013). Remnant calcareous grasslands are often highly fragmented and small in size. Populations in these habitat patches may suffer from reduced probabilities of gene flow and increased genetic drift (Aguilar et al 2008). Habitat loss affects biodiversity at the species level, and the genetic variation of local plant populations (Ouborg et al 2006). We need to identify the key variables influencing genetic variation
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