Interpreting beta diversity components over time to conserve metacommunities in highly-dynamic ecosystems

The concept of ‘metacommunity', or a set of local communities linked by dispersal, has gained great popularity among community ecologists over the last decade. However, whereas metacommunity research mostly addresses questions on spatial biodiversity patterns at the regional scale, conservation planning requires quantifying temporal variation in those metacommunities, and the contributions that individual (local) habitats make to regional dynamics. Here we propose that recent advances in diversity partitioning methods may allow for a better understanding of metacommunity dynamics and for the identification of keystone habitats. First, we show how time series of the two components of beta diversity (richness and replacement), and of the contributions of local habitats to these components, can provide valuable insights into metacommunity dynamics. Second, we apply this framework to a time-series data set of a highly-dynamic model system (an intermittent river) to identify which habitats control source-sink dynamics. Finally, we show how overlooking the temporal component of variation in metacommunity structure may lead to underestimating beta diversity, and we discuss how conservation and metacommunity ecology research in highly-dynamic ecosystems could benefit from studying beta diversity components over time. Adequately appraising spatio-temporal variability in community composition, and identifying sites that are pivotal for maintaining biodiversity at the landscape scale, are key needs for conservation prioritization and planning. Our framework may thus guide conservation actions in highly-dynamic ecosystems whenever time-series data describing biodiversity across sites connected by dispersal are available.