Résumé
Species distribution in a metacommunity varies according to their traits,
the distribution of environmental conditions and connectivity among
localities. These ingredients contribute to coexistence across spatial
scales via species sorting, patch dynamics, mass effects and neutral
dynamics. These mechanisms however seldom act in isolation and the impact
of landscape configuration on their relative importance remains poorly
understood. We present a new model of metacommunity dynamics that
simultaneously considers these four possible mechanisms over spatially
explicit landscapes and propose a statistical approach to partition their
contribution to species distribution. We find that landscape configuration
can induce dispersal limitations that have negative consequences for local
species richness. This result was more pronounced with neutral dynamics
and mass effect than with species sorting or patch dynamics. We also find
that the relative importance of the four mechanisms varies not only among
landscape configurations, but also among species, with some species being
mostly constrained by dispersal and/or drift and others by sorting.
Changes in landscape properties might lead to a shift in coexistence
mechanisms and, by extension, to a change in community composition. This
confirms the importance of considering landscape properties for
conservation and management. Our results illustrate the idea that
ecological communities are the results of multiple mechanisms acting at
the same time and complete our understanding of spatial processes in
competitive metacommunities.