The metacommunity concept invokes the role of species dispersal among local communities in altering species diversity across hierarchical spatial scales. Although metacommunity theory can predict empirical patterns of diversity at local and regional scales, the role of succession in structuring diversity within metacommunities has largely been ignored. Metacommunity theory suggests that species diversity can depend upon the time since initiation of community assembly as the relative influence of regional and local structuring processes changes over succession. Temporal shifts in community composition are predicted to emerge from a greater contribution of regional processes early in succession and a subsequent shift towards local structuring mechanisms late in succession. There are, however, few studies that evaluate the role of habitat age in structuring species richness (‘diversity-age’) over large, fine resolution age gradients of secondary succession in metacommunities. To test theoretical predictions of diversity-age relationships in multitrophic metacommunities, crayfish, fish, and zooplankton species richness and composition along a successional chronosequence in beaver (Castor canadensis) constructed ponds of known age were evaluated. Additionally, the relative contribution of space and the local pond environment to observed differences in community structure across the successional sequence was assessed.
Results/Conclusions
The response of species to the successional metacommunity mosaic depended upon taxonomic group. Crayfish communities were strongly spatially-structured by watershed-level dispersal-limitation and with only weak responses to habitat age and the local environment. In contrast, a unimodal relationship between zooplankton species richness and habitat age was observed among the successional ecosystems despite some isolation by spatial distance in community structure. Analyses of the relative importance of spatial, temporal, and local processes in structuring fish assemblages suggests dispersal and habitat age were more important than local scale drivers. Taken together, these contrasting taxonomic responses to the successional metacommunity mosaic were produced by differential dispersal limitation and structuring by the local environment. Linear trajectories in local environmental conditions defined the successional gradient, where pond area and maximum water depth significantly increased with the number of years since pond formation. The results highlight that succession can influence metacommunity structure, but the relative importance of habitat age varies by taxonomic group and trophic level. Consequently, habitat age and successional stage should be considered important drivers of species diversity across scales in metacommunities.