Regional dynamics of plants: A review of evidence for remnant, source-sink and metapopulations

Despite a long tradition in plant ecology of studies of patch dynamics, recent developments of models for large scale dynamics in source-sink and metapopulations have largely focused on animals. In contrast to mobile unitary animals, many plants resist extinction, even under conditions where only a part of the life cycle can be maintained. This model of remnant population dynamics adds to the two commonly recognized source-sink and metapopulations dynamics. A review of the literature suggests that all three types of dynamics are common in plants. Regional dynamics are related to life-cycle characteristics determining dispersal ability and longevity of life cycle stages. Short-lived or highly habitat specialized plants with good dispersal tend to build up metapopulations, i.e. systems of local populations and non-occupied but potentially suitable sites, interconnected with dispersal, and in a continuous flux of local colonization and extinction. At the other extreme, long-lived plants with clonal propagation, or plants with extensive seed banks, tend to build up remnant population systems, in which many local populations persist over periods long enough to bridge unfavourable phases of successional development, intervening periods of favourable conditions. Source-sink populations are a special case of metapopulations, in the sense that they comprise both persistent refuge populations and ephemeral populations maintained by dispersal. It is suggested that a concept of local population inertia in remnant population systems, scales to higher level phenomena of vegetation inertia, and to community stabilization (through enhanced recovery after perturbations). Such an inertia may contribute to explain cases of exceptionally high species diversity, and lack of pronounced mass extinctions of plants in the fossil record.