COS 101-3 - Disentangling the impacts of changing competitive interactions during climate-driven range shifts

Wednesday, August 9, 2017: 2:10 PM
D129-130, Oregon Convention Center
Jacob Usinowicz, Evironmental Systems Science, ETH Zurich, Zurich, Switzerland and Jonathan M. Levine, Institute for Integrative Biology, ETH Zurich, Zurich, Switzerland

Global climate change drives range shifts that fundamentally alter the nature of biotic interactions, with potentially major impacts on the ability of species to persist. While the impacts of climate change on individual species have been well-studied, we currently lack a predictive framework that makes it possible to anticipate changes in the nature of current biotic interactions and predict novel ones, and account for their impacts. This requires more mechanistic approaches that link changes in species interactions to underlying population processes, but such studies have largely been absent. Here, we introduce a framework based on classic coexistence theory to investigate the impacts of general scenarios of range shifts driven by climate change.


We find that climate-driven range shifts can be grouped into three fundamentally different scenarios according to a shared set of three spatially explicit components of competitive interactions. When ranges track environmental change in space without changing overall area, species persistence is impacted by the spatial offset in peak fitness between competitors, as well as segregation in competition due to limited dispersal. If range area also changes then species may benefit by spatial aggregation of competitive effects when a competitor's range decreases, but suffer when it increases. When a population's spread rate is slower than the rate of environmental change, then a transient negative feedback loop develops; the ongoing decrease in fitness decreases spread rates, which in turn further handicaps fitness, ultimately increasing the likelihood of extinction through time. Although it is difficult to generalize across these three scenarios, we find that the ability of species to segregate in space tends to have the biggest impact overall, as it influences two of the three mechanisms simultaneously. Our results highlight the complicated, non-linear impacts mediated by biotic interactions during range shifts and suggest that common correlative approaches are inadequate for accurate forecasts. However, we also find that impacts can be parsed into a manageable number of distinct mechanisms, which suggest complimentary empirical approaches to disentangle the effects of changing competitive interactions on persistence.