Persistence and coexistence in variable environments: Leveraging abiotic and biotic variation to maintain ecological diversity
Environmental variability and species interactions are two cornerstones in our longstanding effort to understand species coexistence and the mechanisms that maintain biodiversity. Recently, it has become increasingly evident that these two factors are not independent, but rather that environmental variability mediates species interactions. As such, in this talk I examine: how do direct effects of environmental variability versus indirect effects mediated by species interactions (i.e., competition) alter species persistence and coexistence?
I first present a mathematical framework for decomposing the effects of environmental variability and species interactions on coexistence, using a drought-manipulation experiment from California grasslands to examine grass-forb coexistence. I couple this framework with our recently developed method for modeling species interactions in highly diverse ecosystems, with applications from the York Gum Jam woodland understory community from Western Australia. This approach integrates advances in modern coexistence theory and restoration ecology. I show how variability in the environment and species interactions can alter focal species’ low-density growth rates from positive (predicted persistence) to negative (predicted local extinction), informing when—and under what environmental conditions—restoration efforts could result in successful removal of exotics or improved growth rates of natives. Our results highlight the joint impact of abiotic and biotic variation as drivers of species’ demography, species interactions, and coexistence.