Synchrony and tail-dependent synchrony have different effects on the
stability of terrestrial and freshwater communities
Abstract
Global change alters the stability of biological communities by
affecting species richness and how species covary through time (i.e.,
synchrony). There are few large-scale empirical tests of
stability-diversity-synchrony relationships and those mostly focus on
the terrestrial realm. Moreover, the effect of synchrony is largely
unknown when species only covary at either high or low extremes of
abundance (i.e., tail-dependent synchrony), a common phenomenon in
ecological communities. Here, we synthesized long-term community
time-series data (20+ years of species’ abundances/biomass for 2,668
communities across 7 taxonomic groups) from both terrestrial and
freshwater realms and explored how the relationships among richness,
synchrony, and stability vary across realms. We also investigated the
effect of tail-dependent synchrony on stability across 714 freshwater
and 1,954 terrestrial communities. For terrestrial communities, we found
a positive diversity-stability relationship and that the tail-dependent
synchrony was a more important determinant of stability than the
traditional measure of overall synchrony (i.e., based on the covariation
of all species). For freshwater communities, only overall synchrony
explained some variation in stability. Assessing tail-dependent
synchrony can improve our ability to understand why stability varies
across different ecosystems and thereby our inferences about the causes
of human-mediated biodiversity loss.