CONSEQUENCES OF VARYING REGIONAL HETEROGENEITY IN SOURCE SINK METACOMMUNITIES

Mouquet N., Miller T.E., Daufresne T., and Kneitel J.M., (2006).

Oikos, 113, 481-488, doi:10.1111/j.2006.0030-1299.14582.x

Key message : Although 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.

Graphical analysis of competition model with four species. The coordinates represent the quantities of two limiting resources available to the species. We have represented each species’ zero-net-growth isocline and identify species by number. Any equilibrium point on the plane lies on an isocline. The large gray circles are two-species equilibria. The dashed lines define the area of supply points (S1 ,S2 ) which lead to the different equilibria. A supply point represents the level of inorganic nutrients in a system without plant. The bold line shows how we generated the gradient of regional heterogeneity when we connected two communities (A and B) characterized by different resource supply points.

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OTHER TOPICS: Aesthetics of Biodiversity, Biogeography, Macroecology & Ecophylogenetics, Experimental Evolution, Functional Biogeography, Functional Rarity, Nature for Future, Metacommunities, Metaecosystems, Reviews and Synthesis, Trophic Biogeography & Metaweb