Long-distance seed dispersal and seed banks contribute to within- and among-site diversity patterns in a grassland metacommunity.
Vandvik, Vigdis*,1, 2, Goldberg, Deborah1, 1 Department of Ecology and Evolutionary Biology, Ann Arbor, MI, USA2 Department of Biology, Bergen, Norway
ABSTRACT- A current controversy in community ecology concerns whether patterns in diversity within and among communities emerge primarily as results of local processes (interactions, niche dimensions) or regional dynamics (dispersal and local extinctions). Insights from metapopulation ecology suggest that we should focus on how local and regional processes interact, and try to identify the conditions that would result in changes in these interactions between local communities. We studied the contribution of different sources of recruits to the diversity of gap-colonizing communities in subalpine grasslands, and explored changes in the relative importance of these sources along a successional (disturbance) gradient. Specifically, we quantified the minimum dispersal distances of each species appearing in experimental gaps using data on the composition of the vegetation (within local patch, among patches within site, outside local community) and local seed banks (short-term, long-term). Seed sources other than the current vegetation of the local patch (i.e. seeds dispersed through space and/or time) accounted for an appreciable 38-58% of the seedling diversity, long-distance dispersal alone accounted for 13-21%. The diversity of local recruits decreased during succession, resulting in increased relative contributions of recruitment from long-distance dispersal and the seed bank. Ecological traits (e.g. seed mass, seed-bank persistence) of recruits from different sources, and changes in these during succession, were explored. As long-distance dispersal and seed banks made significant contributions to the diversity and composition of these grasslands, and as their relative importance changed with successional context, we conclude that these sources of diversity need to be taken into account in order to fully understand local communities.
Key words: disturbance, seedbank, dispersal, diversity
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