COS 22-1
Multi-scale coexistence under spatially variable environments
Revealing mechanisms that maintain competitive coexistence explains crucial drivers of biodiversity. However, there have been few rigorous tests of general coexistence mechanisms applicable to a broad spectrum of ecological systems. Moreover, multi-scale studies are much needed to reconcile the debate over whether small scale (e.g. local) or large scale (e.g. regional) coexistence drives diversity patterns.
We empirically test the hypothesis that population fluctuations driven by environmental variation at smaller scales give rise to a general coexistence mechanism, the spatial storage effect at larger scales promoting stable coexistence between competing species. This mechanism links smaller and larger scale processes and include functional ingredients that express the degree of intensification of intra relative to interspecific competition. Direct measurements on those ingredients introduce unprecedented rigor and confidence to testing coexistence.
We focus on a community of desert winter annual plants co-occurring across a hierarchical range of spatial scales (neighborhood → subhabitat → habitat → landscape).We quantify the strength of the spatial storage effect through multi-scale measurements of demographic variables of a few focal species under density and competition manipulation.
Results/Conclusions
Two years results suggest that the presence of the mechanism can be absent at smaller scales but present at larger scales, and therefore is scale dependent. Moreover, this dependency on spatial scale can change over years and is thus subject to spatiotemporal variation. The results support our prediction and emphasize the influence of relatively large scale (i.e. between-habitat) processes. The influence by spatiotemporal variation suggests more theoretical and empirical investigation is needed to understand the interaction between spatial and temporal environmental variation in promoting species coexistence.