Genomic demography predicts community dynamics in a temperate montane forest

Species population sizes fluctuate over time, and these temporal dynamics play a key role in governing the maintenance of biodiversity. Although modeling approaches have been developed to characterize fluctuations in species abundances, the data required to parameterize these models from scratch are substantial. Here we introduce a new approach to modeling population fluctuations on decadal timescales by relating community-level dynamics to population-level patterns encoded in plant genomes. Using genomic samples taken at a single time point to generate contemporary effective population size estimates in a temperate montane forest, we accurately predict fluctuations across three censuses. Our approach facilitates the use of genomic demography to parameterize multispecies community models in ecology and shows that population genomic data can provide accurate predictions for ecological dynamics.