Investigating genetic factors behind the decline of a threatened plant species – Tephroseris integrifolia (Asteraceae)

Landscape change in Europe has caused the decline of many grassland species. Tephroseris integrifolia (Asteraceae) is one species which has declined rapidly in Sweden since the 19th century. A census of extant populations from 1980 to 2009 revealed a dramatic decrease in population sizes during the early 1990s, despite far-reaching conservation measures. Knowledge of causes of species decline is necessary for the elaboration of conservation programmes. In this thesis, it is investigated whether this ongoing decrease is caused by a decreased genetic variation within North European T. integrifolia populations, with the main focus on Sweden. The Swedish populations showed only weak signs of inbreeding depression, and the plants were capable of setting seeds after within-patch cross-pollination, indicating that very little genetic variation has been lost. The Swedish populations did not differ from Estonian populations in variation in AFLP markers, and there was no connection between population size and local genetic variation. When compared with British and Danish populations, heritability (i. e. quantitative expression of genetic variation) was for most characters the largest in the Swedish populations, which are the smallest and the smallest for the Estonian populations, which are the largest. Though Swedish T. integrifolia populations have not lost much genetic variation, the high heritability indicates that they might be in the early stages of a bottleneck. The ongoing decline of T. integrifolia in Sweden does probably not have genetic causes. Rather, the causes of species decline can be found in the altered dynamics of the cultural landscape