Data from: Community composition as an overlooked driver of spatial population synchrony

Animal populations often display coherent temporal fluctuations in their
abundance, with far-ranging implications for species persistence and
ecosystem stability. The key mechanisms driving spatial population
synchrony include organismal dispersal, spatially correlated environmental
dynamics (Moran effect), and concordant consumer-resource dynamics.
Disentangling these mechanisms, however, is notoriously difficult in
natural systems, and the extent to which the biotic environment (intensity
and types of biotic interactions) mediates metapopulation dynamics remains
a largely unanswered question. Here, we test the hypothesis that
compositional differences among communities (i.e, beta-diversity), used as
a proxy of the differences in biotic interactions experienced by separated
populations, reduces population synchrony. Using an extensive dataset of
fish population abundance time-series across Europe, we provide evidence
that higher beta-diversity is associated with reduced spatial population
synchrony within river networks, and demonstrate that these effects are
independent from geographic separation, environmental dissimilarity, and
Moran effects. Although beta-diversity is commonly shown to promote
metacommunity stability by reducing spatial synchrony in aggregate
community attributes (e.g., total biomass), our study indicates that
compositional heterogeneity provides a previously overlooked spatial
insurance effect that influences metapopulation dynamics by promoting
asynchrony between populations separated in space. These findings
illustrate how community assembly across different locations within river
networks contributes to metapopulation stability and persistence of
individual species, and further highlights the implications of the loss in
beta-diversity over time via biotic homogenisation.