Large-scale spatial dynamics of plants: metapopulations, regional ensembles and patchy populations

1 We present a critical review of the application of metapopulation theory to the regional dynamics of plants. We consider whether there is evidence that regional populations of plants show a metapopulation structure. We then review the alternatives to the metapopulation regional population structure for plants. 2 Although metapopulation theory primarily deals with regional dynamics, it is, however, also commonly applied to patch dynamics within local populations ('metapatch' systems). These apparently analogous systems are very different: systems of patchy local populations do not exhibit the dissociation of processes operating at different spatial scales that is characteristic of metapopulations. 3 The parameters of classical metapopulation studies, such as colonization, re-colonization and extinction, may be hard to measure for many plant populations, in particular for populations with long-lived seedbanks. 4 The assumption of metapopulation theory that suitable habitat occurs as discrete patches within a matrix of unsuitable habitat is not always true, as regional populations of some species may exist on largely uninterrupted swathes of suitable habitat. Alternatively, suitable patches may be hard or impossible to define a priori. 5 Using detailed case studies from the literature we outline a possible classification of the spatial dynamics of plants at both regional and local scales. 6 At the regional scale we define: metapopulations, in the classic sense, where regional persistence is governed by the processes of patch colonization, extinction and recolonization; regional ensembles, systems of essentially unconnected local populations persisting in an ill-defined mosaic of suitable and unsuitable habitat; and spatially extended populations, essentially a single extended population occupying large tracts of suitable habitat, but whose regional dynamics are essentially a simple extension of local dynamics. 7 Although a range of forms of local spatial dynamics exist, these are qualitatively different from the forms of population structure at the regional level.