Habitat matrix effects on the structure and dynamic of the metacommunity in two different regions

The metacommunity concept supposes that species occurrence depends on species dynamics and interactions at the local and the regional level via the movements of individuals among localities. For species with complex life cycles, such as several amphibian species, not all required resources are contained in the breeding habitat, and some species depend on terrestrial habitat to complete their life cycles. As animal movement can also be influenced by the physical quality of the matrix to be crossed to reach the breeding habitat and on the affinity of a species for specific terrestrial habitats, it is reasonable to expect that different matrix characteristics act either to enhance or to hinder dispersal success. These effects on dispersal success would logically be expected to impact on the species’ composition of larvae assemblage at local level and, in consequence, to determine metacommunity structure and dynamic. We tested to determine whether two metacommunities with the same species pool along similar freshwater gradients exhibited different structures and dynamics in two regions that were well differentiated in terms of their respective terrestrial matrix. Our observation was that in the heterogeneous region all species showed lower co-occurrence than in the homogeneous region. Local extinction and colonisation rates were also higher in the homogeneous region. Abundances of tadpoles at local level in the homogeneous region were determined principally by the local process (pond permanence, predation risk and competition) whereas, in the heterogeneous region, abundances were explained in part by landscape factors. Differences observed in the structure and the dynamic of metacommunities between the two regions demonstrated the importance of inter-patch matrix heterogeneity for organisms with complex life cycles.