Surrounding landscape structures, rather than habitat age, drive genetic variation of typical calcareous grassland plant species

Abstract

Context Land 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. Objectives The 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. Methods We investigated 912 individuals, 304 per study species, from 19 calcareous grasslands across the Swabian Alb in Baden-Württemberg (Germany) using AFLP analyses. Results We 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. Conclusions Migratory 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.

Habitat matters – Strong genetic and epigenetic differentiation in Linum catharticum from dry and wet grasslands

“…With a mean Nei's gene diversity of 0.078 over all sites, genetic diversity was lower than we would have expected, even for a mainly self‐pollinated species (Reisch & Bernhardt‐Römermann, 2014). In the previous study of L. catharticum from 19 calcareous grasslands, mean genetic diversity was estimated at 0.155 (Lehmair et al, unpublished), which is more in accordance with the values expected for rather common species. However, the present dataset includes many private fragments, only present in study sites from one or the other habitat type.…”

“…Even though genetic diversity was lower than epigenetic diversity, differentiation was higher on the genetic than on the epigenetic level. In our previous study, on L. catharticum from calcareous grasslands across the Swabian Alb (max distance among sites: 85 km) variation among study sites was estimated at 8% (Lehmair et al, unpublished). These findings present tremendous differences compared to the levels of differentiation found between the two different habitats.…”

“…To investigate the genetic and epigenetic differences due to habitat, we collected plant samples from two habitats on opposing ends of the moisture spectrum: calcareous grasslands and litter meadows. In a previous study (Lehmair, Pagel, Poschlod, & Reisch, unpublished), we analyzed the genetic variation of L. catharticum from 19 calcareous grasslands across the Swabian Alb and found intermediate levels of genetic diversity and low levels of genetic differentiation among study sites. We did not detect any indication for isolation by distance, despite the considerable maximum distance of 85 km among sites.…”

The impact of environment on genetic and epigenetic variation inTrifolium pratensepopulations from two contrasting semi-natural grasslands

“…Previous studies about genetic diversity patterns in common CG [ 64 ] and OM plant species [ 65 ] observed a trend to higher genetic diversity levels in CG populations. Within the study region, CGs are still managed by migratory sheep herding and are, thus, exposed to elevated levels of disturbance by grazing and trampling.…”

Landscape genetic analysis suggests stronger effects of past than current landscape structure on genetic patterns of Primula veris

“…Fragmentation and loss of habitats often impose serious negative effects on genetic diversity because they potentially lead to reduced gene flow between populations and increased inbreeding and genetic drift (Honnay & Jacquemyn, 2007; Leigh et al, 2019; Leimu et al., 2006; Prentice et al., 2006; Young et al., 1996). Increasing application of landscape genetic tools has advanced knowledge about the influence of environmental heterogeneity on genetic diversity and demonstrated that, in addition to geographic isolation, also the characteristics of the landscape around and between plant populations can strongly shape genetic patterns of plants (Emel et al, 2020; Holderegger et al., 2010; Lehmair et al., 2020; Manel et al., 2003). This knowledge is also crucial for the recovery of resilient populations during ecosystem restoration (Moreno‐Mateos et al., 2020).…”