Consequences of varying regional heterogeneity in source–sink metacommunities

International audienceAlthough the influence of dispersal on coexistence mechanisms in metacommunities has received great emphasis, few studies have addressed how such influence is affected varying regional heterogeneity. We present a mechanistic model of resource competition in a metacommunity based on classical models of plant competition for limiting resources. We defined regional heterogeneity as the differences in resource supply rates (or resource availabilities) across local communities. As suggested by previous work, the highest diversify occurred at intermediate levels of dispersal among local communities. However our model shows how the effects of dispersal depend on the amount of heterogeneity among local communities and vice versa. Both regional and local species richness were the highest when heterogeneity was intermediate. We suggest that empirical studies that found no evidence for source–sink or mass effects at the community level may have examined communities with limited ranges of dispersal and regional heterogeneity. This model of species coexistence contributes to a broader understanding of patterns in real communities

Small-scale patterns in community structure of Sarracenia purpurea inquilines

We examined the environmental factors associated with community structure in the inquiline communities of the purple pitcher plant (Sarracenia purpurea L.). We sampled all 141 communities in a 10- x 20-m grid and recorded their spatial relationships to determine the relative influence of environmental and spatial factors on community structure. Environmental and spatial factors contributed equally to the variance in community composition (species identity and abundance) among pitchers.  The species richness of communities was influenced by both spatial and environmental variables, particularly environmental variables related to community size. In addition, our study suggests a number of hypotheses about factors influencing community structure (e.g. predation) that could be tested experimentally

Allometry of Body Size and Abundance in 166 Food Webs

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