Synchronous dynamics (events operating in unison) are universal phenomena with widespread implications for ecological stability of populations, communities, and ecosystem functions. In ecological communities, synchronous fluctuations in abundances among species can amplify the destabilizing effect of environmental variability on ecosystem functions such as net productivity. The inverse dynamic—compensation—can stabilize function, as species’ respond in opposite manners to underlying drivers. Yet, describing and explaining these phenomena remains an ongoing challenge, in part because community synchrony is an emergent property of diverse species interacting with one another and responding to multiple, simultaneous environmental drivers. Critically, species fluctuations may be synchronous on one timescale but compensatory on another. Likewise, they may be highly synchronous in certain life history stages or in species’ responses to certain environmental conditions but less synchronous in others. Here, we combine a novel model of community dynamics, that incorporates multiple underlying environmental drivers, competitive dynamics, and dispersal between locations, with a newly developed timescale-specific variance-ratio approach to examine the interplay of environmental and biotic variables on synchrony across timescales.
Results/Conclusions
Using our model to examine synchrony of communities in which species exhibit a variety of growth strategies, we show that—even when species respond synchronously to environmental drivers—underlying differences in growth strategies can alter community patterns. When some species exhibit lagged growth, the community will exhibit compensation at short timescales and reduced synchrony at long timescales. In comparison, when some species exhibit rapid growth causing them to overshoot their carrying capacity, the community maintains synchrony in short, but not long, timescales. We additionally explore how changing climatic conditions—rather than assuming stable underlying environmental drivers—can alter timescale patterns of synchrony, masking the timescales of environmental fluctuations. Finally, we show that spatial processes such as dispersal between locations with different underlying drivers, can be detected using a timescale-specific variance-ratio. Overall, we find that the classic variance ratio is biased towards long-term drivers and may miss the importance of short-term drivers of synchrony or compensation. These short-term drivers may be crucial for patterns of stability and resilience, highlighting the importance of considering drivers operating on multiple timescales when examining patterns in community synchrony.