Abstract
Knowledge of genetic diversity and connectivity within and between populations of specialist meadow plants is crucial to developing effective conservation strategies at the landscape-scale. This study investigated levels of genetic diversity within, and gene flow between populations of a key annual species, Rhinanthus minor in protected meadows and landscape matrix sites in two contrasting regions. Possible barriers to gene flow were also analysed. Leaf material from 714 individuals in an extensively managed upland region and an intensively managed lowland region of the UK was genotyped using microsatellite markers. Genetic diversity was similar in the two regions (He = 0.48 and 0.44). FST values indicated population differentiation in both regions but the estimate was higher in the lowland (FST = 0.28) than in the upland region (FST = 0.19); evidence of global structure was revealed in a spatial principal components analysis but a maximum likelihood population effects model did not identify significant predictors of population differentiation after testing the effects of Euclidean geographic distance, land cover and elevation. Conservation strategies should aim to maintain large populations in meadows to enhance genetic diversity. At the same time the focus should be on existing and additional species-rich grassland fragments, particularly in areas of intensive land-use, if genetic connectivity is to be retained.
Highlights
Habitat fragmentation is detrimental to genetic diversity as well as species diversity (Kahilainen et al 2014; Schlaepfer et al 2018)
This study investigated the level of genetic diversity in protected meadow sites, and analysed gene flow to examine the extent to which protected meadows and landscape matrix sites were functioning as a meta-population
This study has shown that populations of a key meadow species, R. minor have intermediate levels of genetic diversity which are comparable with other studies of this species, and that they have relatively high levels of inbreeding
Summary
Habitat fragmentation is detrimental to genetic diversity as well as species diversity (Kahilainen et al 2014; Schlaepfer et al 2018). Investigations into the impact of fragmentation have included the examination of relationships between patch size and species richness, the analysis of the influence of past landscapes and habitats, the role played by land use and management of isolated sites, and the study of various aspects of functional connectivity (Krauss et al 2004; Purschke et al 2014; Auffret et al 2015; Huber et al 2017) Such approaches will be complemented by studies of the loss of functional connectivity through gene flow, since reductions in genetic variability within populations, and genetic divergence between populations, are likely to be associated with isolated habitat patches (Young et al 1996). Such populations are likely to be more susceptible to genetic drift, higher levels of inbreeding and reduced gene flow between populations (Ellstrand and Elam 1993) and it has been recommended that the impacts of reduced genetic diversity on fitness and the responses of populations to environmental change should not be overlooked in conservation strategies (Hooftman et al 2003; Jump et al 2008)
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