Clonal diversity and genetic differentiation of <Emphasis Type="Italic">Maianthemum bifolium</Emphasis> among forest fragments of different age

Maianthemum bifolium Schmidt (May Lily) is a woodland species with low colonisation ability and high demands for seedling establishment conditions. To study the colonisation process, we analysed the clonal organisation and population structure of Maianthemum bifolium populations in a number of forest fragments using AFLP. A total of 129 genets were identified. Most (41/53) patches of M. bifolium in recent (less than 80 years old) and old (at least 175 years of age) parts of the woodlands contained single genets. Only one of the 12 patches with multiple genotypes showed intermingled growth. Besides seed dispersal also dispersal of vegetative material contributed to colonisation since five genotypes were found in more than one patch, with patches up to 51 m apart. Population differentiation between populations in different forests was significant (F_ST = 0.10) and indicated low gene flow. This level of differentiation was already found between populations in different parts of the same forest, just over 200 m apart. In fact, only two adjacent populations were not significantly differentiated, one population located in old forest whereas the other was established next to it on a former pasture re-forested after 1916. Limited gene flow is also consistent with the decrease of genetic similarities with physical distance, which relationship is highly significant but only for distances up to 400 m.