META-POPULATION DYNAMICS OF BIENNIAL PLANTS - HOW TO EXPLOIT TEMPORARY HABITATS

Extinction of local populations of plants of many biennial plant species has been frequently reported. Survival of these species on the meta-population level implies a balance between extinction and regeneration, either through seed dispersal or from the seedbank. We distinguish between three types of biennials (transient, fugitive and persistent) and review the relation between dynamics of local populations and habitat characteristics, such as disturbance. Some species are safe-site limited whereas other species demonstrate a combination of safe-site and seed limitation. Meta-population dynamics are illustrated with two examples (Senecio jacobaea and Cynoglossum officinale). We distinguish between patch dynamics (loss and genesis of sites that are suitable for population development) and meta-population dynamics of biennials (population behaviour within and between sites, and dispersal). A hypothesis is developed on the regulation of patch dynamics. Finally we discuss the question: what makes biennials suited for exploiting temporary habitats?