Nestedness, niche metrics and temporal dynamics of a metacommunity in a dynamic natural model system

Prediction of extinction and colonization rates for whole species assemblages emerges as an urgent task for ecology. We hypothesized that nestedness of species assemblage reflects differential ability of species to occupy sites and of sites to support species. If correct, a nested ordering of species and sites should condense long-term dynamics of metacommunities. To test this we characterized the differential ability of species to use habitat (niche position and niche breadth) using eight surveys of invertebrate communities inhabiting 49 tropical rock pools. We examined temporal consistency of the nested rank of species and pools, and related them to species and pool characteristics to infer temporal dynamics of species composition. Invertebrate assemblages in the rock-pools were significantly nested and species ranks were generally preserved over time. By contrast, pool ranks were usually conserved between adjacent years only but their similarity declined with time separating surveys. The nested species-by-pool matrix of the first survey served as a benchmark to assess individual species and local community changed in subsequent years. As hypothesized, benchmark cells with high state occupancy probability had low extinction rates in subsequent years. Moreover, species high in the nested matrix (also with high regional occupancy probability) were better survivors and colonizers relative to species that ranked low. The year-to-year dynamics were similar. Species with non-marginal niche position retained high ranks in the matrix. Yet, niche position predicted only colonization rate of species. Niche breadth and species' nested ranking, extinction risk, or ability to colonize a pool showed no relationship. Counter to the expectation, pool ranks did not predict species extinction and colonization rates. Apparently, even in dynamic systems, regional nested pattern remains consistent and the underlying extinction and colonization dynamics appear to be largely determined by the hierarchical order among species and much less by that among sites.