At minor species the pollen density in small stands remains low. As the density declines rapidly along distance, gene flow among scattered stands and trees is expected to be very low. Nevertheless, migration pressure is the ratio between foreign and own gametes of the population. If also the within stand pollination is scarce, even a small amount of immigrating pollen can result in a significant migration pressure. Pollen and seed dispersal will be measured in various natural stands.
Selection acts on adaptive traits.
However, this ratio is not equal to the selection intensity. Most of the losses are due to random incident, such as seed predation. In competition experiments, which will be established within this project, the success of individual plants will he compared with the results of measurements on adaptive trails. This project approaches the maintenance of genetic diversity from several viewpoints. Our synthesis aims at estimation of the relative importance of each factor.