SYMP 17-4 - Patterns of coexistence and species diversity in spatiotemporally varying environments: Comparisons of short-, long-lived, and seedbanking plants

Ecosystems are highly dynamic, with large spatiotemporal variability in the abiotic environment (e.g. temperature, precipitation) as well as in biotic interactions and competitive neighborhoods. Seed banks and other life history strategies that allow species to “store” individuals during poor conditions are considered key mechanisms for the maintenance of biodiversity. Despite the importance of storage in poor environmental conditions, how seed banks alter patterns of alpha, beta, and gamma diversity in metacommunities nor a comparison of coexistence mechanisms that maintain biodiversity have been quantified across different storage life history strategies. Here, we first use a stochastic simulation based metacommunity model to examine how diversity in spatiotemporally varying environments depends jointly on seed bank dynamics (i.e. germination and seed survival rates) and dispersal rates. We find that seed banks promote local diversity when seed survival is high and increase gamma diversity when moderate or high dispersal rates are coupled with low germination rates. Next, we examine the mechanisms that promote storage in variable environments across different life history strategies from seed banking annuals to perennials with an adult storage stage. We compare both strategies to non-seed banking annuals as a baseline. To do so, we create demographic models of each life history strategy and partition the role of fluctuation dependent mechanisms of coexistence (temporal nonlinearity in growth, nonlinearity in competition, and the temporal storage effect), quantifying their contributions across a gradient of environmental conditions. We show that fluctuation dependent mechanisms in general and the storage effect in particular can be equally important in coexistence patterns for perennial species as for seed banking annual species. The storage effect is a particularly strong mechanism of coexistence when the perennial species is the resident competitor, as adults can exert competitive effects even during a non-favorable year. Overall, our results highlight that storage alters classically considered metacommunity diversity patterns and that storage, whether through seed banks or long lived perennials, buffers diversity and stability under variable environmental conditions.