Incorporating interspecific interactions into phylogeographic models: A case study with Californian oaks

It has been long assumed that abiotic factors (i.e., geography and climate) dominate the ecological and evolutionary processes underlying the distribution of species, lineages and genes at broad spatial scales and, as a result, the study of interspecific interactions has largely been overlooked in biogeography research and ignored entirely in phylogeographic inference. Here, we focus on plant-plant interactions and test whether their demographic consequences translate into broad-scale patterns of genomic variation in two Californian oak species. With our process-based analyses and statistical comparison of the likelihoods of alternative models, we show that spatial patterns of genomic variation are better explained by demographic scenarios incorporating interspecific interactions (including both competition and facilitation) than by null models that only consider heterogeneity of environmental suitability across the landscape. Collectively, our integrative approach supports the notion that the consequences of biotic interactions transcend much larger geographical and evolutionary scales than the traditional local focus.