The geographic scale of genetic variation in common plant species – Implications for genebanks and restoration

Genebanks for plant seeds are a necessary tool to support the conservation of biodiversity. In the last decades also the importance of intraspecific diversity within the genebank collections was emphasised. Even though background information on the distribution of genetic diversity within and between populations was scarce for common plant species, seed provenances have been delineated for seed collection and production. Seeds have to be used in the same provenance, where they were collected for restoration projects, agriculture and forestry. The present study aims to elucidate distribution of intraspecific genetic diversity in three common plant species over different geographic scales. In the last part, further intraspecific differences in seed traits were investigated. Chapter 2 dealt with the distribution of genetic diversity within and between populations of Sedum album in its distribution range in Europe and the history of Central European populations. With a combination of neutral and chloroplast specific markers, we reconstructed postglacial processes that lead to the present distribution pattern in S. album. Distinct haplotypes could be detected on the Iberian Peninsula and in Eastern and Southern Europe. Central European populations have their origin in Southern Europe and show meanwhile high influence of Eastern lineages. A clear East/West subdivision was found with hybrid zone in Western Europe. Glacial refugia have been detected on the Iberian Peninsula and in the mountains of Liguria (Northern Italy). Further refugia can be assumed in south-eastern Europe, and northern refugia in small-scaled areas in Germany and Eastern Europe. In chapter 3 and 4 we used AFLP markers to examine the distribution of genetic diversity in and between populations of Lathyrus pratensis and Hepatica nobilis in Bavaria. Correlation of genetic diversity with seed provenances was tested. The studies of two perennial, cross-pollinated plants revealed differences in genetic diversity within and between populations. In L. pratensis within population diversity was ordinary compared to other plants with similar life history traits. However, differentiation between populations was very high, what can be ascribed to the limited dispersal of the heavy seeds. Moreover, the influence of nearby anthropogenic populations can, therefore, be excluded. Gene flow was present within 110km, resembling the northern and the southern part of Bavaria (delineated by the river “Danube”). We found that the group of populations in southern Bavarian is located in and delineated by one of the official seed production areas. For L. pratensis the production zone is sufficient. Nevertheless, material for restoration should be taken as near as possible due to high differentiation between populations. Collections for genebanks should be undertaken from both northern and southern Bavaria, with an emphasis on southern parts, where genetic variation within populations was higher. For H. nobilis, there were no correlations with official provenances or production zones. Gene flow was very limited, obviously due to the seed dispersal by ants, which agitate within few square metres. Genetic diversity within populations was high, while differentiation between populations was moderate. The pattern can be explained by random, long-distance dispersal, e.g. of plants, which have been used in horticulture for many centuries. Because ex-situ storage of seeds is difficult for H. nobilis, it is important to conserve high variation in in-situ populations in old forests. Intraspecific differences in seed traits were examined in chapter 5. Seed quality and longevity were tested in two experimental setups. We measured percentage of filled seeds with x-ray analysis, 1000-seed-weight, initial and maximum germination rates to infer seed quality. To measure longevity seeds were conducted to accelerated aging. We collected data from wild lowland and alpine populations and from common garden populations, which were cultivated from seeds of the same populations. Percentage of filled seeds and seed weight was not different for lowland and alpine, or wild and common garden populations. Nevertheless, initial and maximal germination was higher in seeds from wild populations. Further, longevity tended to be higher in seeds from lowland than alpine and common garden than wild populations, respectively. Nevertheless, we could show that differences in longevity are environmentally influenced to some extent, because common garden populations of different origin differed less than wild populations. In a second setup, seeds were collected in consecutive years from the same populations. Seed data were compared with climate data. We used model approaches based on results of former studies. Mean annual temperature and total annual rainfall, and mean annual temperature together with total rainfall and total sunshine within 90 days prior to harvest explained some variation in our data. In chapter 6, I conclude that history of populations and plant traits have more influence than recent anthropogenic events on the distribution of genetic diversity in common plants. For conservation of intraspecific diversity in common plants, plant traits should be considered in collections for genebanks and in the usage of seeds for restoration. The collection of more data concerning quality and longevity of wild plant species would improve future collections. Costs for testing, regrowth and recollection in genebanks would be reduced.