European semi-natural grasslands are among the most species rich habitats in the world. They were historically shaped by anthropogenic land use and developed their species and genetic variation alongside the agricultural practices of the time. The lasting effects of historic processes can be ob-served until today, however recent global developments are affecting this diversity in an unprece-dented intensity and frequency. The present study aims to investigate the effects of land use his-tory, landscape structure as well as vegetation and habitat characteristics on genetic and epigenetic variation of common grassland species from different grassland habitats.
Chapter One introduces the scientific context the present thesis is placed in. Processes shaping biodiversity, the characteristics of the grassland ecosystems studied in this thesis and the history of grassland ecosystems in general is reviewed. Finally, grassland habitats are discussed in the context of biodiversity and conservation.
In Chapter Two and Three the influence of land use history, landscape structure and habitat quality on the genetic variation of typical grassland species from oat-grass and litter meadows was investi-gated. We used Amplified Fragment Length Polymorphism (AFLP) analyses to estimate genetic diversity and differentiation among populations from ancient and recent grasslands.
Chapter Two describes the genetic variation patterns of three typical grassland species (Dactylis glomerata L., s. I., Heracleum sphondylium L. & Trifolium pratense L.), studied in oat-grass mead-ows. Each species was influenced by different explanatory variables, but most interestingly current landscape structure and habitat quality, i.e. the amount of litter, influenced genetic diversity in this grassland habitat. Historic landscape structure and land use history were of minor interest in this comparably recently established grassland type.
Similarly, Chapter Three deals with the genetic variation in litter meadow plant species (Angelica sylvestris L., Filipendula ulmaria (L.) MAXIM & Succisa pratensis MOENCH). Historic as well as recent gene flow patterns influenced genetic variation of the species in this ecosystem, highlighting the current importance of historic processes. However, the most important process, from a conserva-tion point of view, was the extensive gene flow produced by seed transfer via mowing machines.
Extending the study of the intraspecific variation in grassland ecosystem to the epigenetic level, the genetic as well as epigenetic variation in Linum catharticum L. from different contrasting habitats is presented in Chapter Four. Combining AFLP and Methylation Sensitive Amplification Polymorphism (MSAP) analyses, large differences among populations from wet litter meadows and dry calcareous grasslands were observed, which could not be explained by geographic distance alone, but rather by the different local habitat conditions. This result highlights the impact of local environmental conditions on the genetic as well as the epigenetic level, which likely led to the development of different ecotypes.
In Chapter Five the results of the three main chapters are reviewed in the context of nature con-servation. Historic as well as current gene flow processes were found to be important determinants of current genetic variation in common grassland species. Additionally, various local environmental factors contributed to the genetic as well as epigenetic variation patterns.
In conclusion, genetic diversity in different grassland ecosystems and their respective species are influenced by different historic and present processes. Thus, conservation strategies should pay tribute to historic land use practices and stochasticity, while decreasing the impact of current pro-cesses of fragmentation and habitat loss, to increase gene flow among remnants of species-rich grasslands. Additionally, appropriate management will enhance the habitat quality, thus improving the establishment of new individuals, thereby increasing genetic variation. Different practical con-cepts, such as autochthonous seed material and genetic conservation areas can play an important role in preserving genetic variation for grassland species
