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Convergence and divergence in pond meta-communities: Implications for local and regional patterns of diversity.
Chase, Jonathan1, 1
ABSTRACT- Do similar communities develop on similar sites? Two views of community assembly place different emphasis on the local environmental conditions or the regional context (e.g. the rate and timing of species colonization) within which local sites are embedded. If local conditions predominate, communities with the same species pool will converge towards a single community configuration, regardless of differences in the regional context. Alternatively, if regional processes predominate, communities can diverge towards alternative stable states. These contrasting views can have important implications for patterns of diversity at local and regional scales within a meta-community. Using theoretical predictions and empirical evidence from surveys and experiments in small freshwater ponds, I show that: (1) Communities that have harsher conditions, such as low productivity or high rates of disturbance, tend to converge towards a single community configuration, while communities with more favorable conditions, such as high productivity and low rates of disturbance, tend to diverge towards alternative stable communities. (2) Communities that are more connected to one another tend to converge in community composition. (3) The convergence and/or divergence of local community structure has important implications for patterns of biodiversity at local and regional scales. For example, increased divergence among local communities at higher levels of productivity can lead to scale-dependent productivity-diversity relationships. Also, higher colonization rates among local ponds can sometimes increase local diversity, but decrease regional diversity.
KEY WORDS: meta-community, local diversity, regional diversity, pond