Fish community trait dissimilarity dampens synchronizing effect of environmental fluctuations

Spatial synchrony, defined as the synchronized temporal fluctuations in
species or community abundances across different locations, has
implications for ecological persistence and stability and has received
renewed attention in the context of rapid environmental changes. It is
shaped by both biotic and abiotic drivers, with shared environmental
fluctuations expected to promote synchrony in population dynamics, and
dissimilarity in species composition expected to enhance asynchrony.
Exploring spatial synchrony using trait-based approaches may provide new
insights into the underlying drivers of community dynamics. Here, we
investigated the drivers of spatial synchrony in the thermal affinity of
fish communities (i.e., thermal community synchrony) within river basins
in Europe, Australia, and the United States using multi-membership mixed
models accounting for spatial, environmental and community dissimilarity.
Our results show that synchrony in fish community thermal affinity
decreases with watercourse distance, similar to spatial decays documented
for spatial synchrony in population abundance. Thermal community synchrony
also increases with synchrony in air temperature, emphasising the role of
environmental forcing. However, community composition moderated this
forcing, such as greater trait dissimilarity dampened the synchronizing
effect of temperature. These findings highlight the interconnected
influence of environmental synchrony and community trait composition and
the importance of integrating both environmental and community-level
factors to better understand metacommunity responses to spatially
synchronized environments.