Genetische variatie bij mossen: oorsprong en mechanismen van handhaving

The advance of molecular techniques and mathematical models offers great opportunities for new developments in bryophyte population ecology, but ample scope remains for contributions by amateurs (field observations, experiments). A simple simulation model suggests that in clonally reproducing plant populations in steady state genetic variation will decline rapidly due to random drift, but this is not always confirmed by field data. We are beginning to understand the mechanisms behind positively and negatively density-dependent effects in bryophyte communities, but the consequences for the maintenance of genetic variation of positive density dependence in particular have hardly been studied until now. Other important developments in bryophyte population ecology include 1) the application of the metapopulation concept and the analysis of processes which are crucial in this context such as dispersal, establishment and mortality; 2) further studies on the size and genetic composition of the diaspore bank; and 3) relative reproductive success of males and females.