Fragmented dry grasslands preserve unique components of plant species and phylogenetic diversity in agricultural landscapes

In intensively used landscapes biodiversity is often restricted to fragmented habitats. Exploring the biodiversity potential of habitat fragments is essential in order to reveal their complementary role in maintaining landscape-scale biodiversity. We investigated the conservation potential of dry grassland fragments in the Great Hungarian Plain, i.e. patch-like habitats on ancient burial mounds and linear-shaped habitats in verges, and compared them to continuous grasslands. We focused on plant taxonomic diversity, species richness of specialists, generalists and weeds, and the phylogenetic diversity conserved in the habitats. Verges meshing the landscape are characterised by a small core area and high level of disturbance. Their species pool was more similar to grasslands than mounds due to the lack of dispersal limitations. They held high species richness of weeds and generalists and only few specialists. Verges preserved only a small proportion of the evolutionary history of specialists, which were evenly distributed between the clades. Isolated mounds are characterised by a small area, a high level of environmental heterogeneity, and a low level of disturbance. Steep slopes of species accumulation curves suggest that high environmental heterogeneity likely contributes to the high species richness of specialists on mounds. Mounds preserved the same amount of phylogenetic diversity represented by the branch-lengths as grasslands. Abundance-weighted evolutionary distinctiveness of specialists was more clustered in these habitats due to the special habitat conditions. For the protection of specialists in transformed landscapes it is essential to focus efforts on preserving both patch-like and linear grassland fragments containing additional components of biodiversity.