COS 5-6
Does intraspecific trait variation mediate the relative importance of selection, drift, and dispersal as drivers of beta-diversity?
A key goal of ecology is to disentangle multiple drivers of community assembly across spatial scales. Spatial variation in community composition, known as beta-diversity, can provide insights into how assembly processes such niche selection across environmental gradients, dispersal limitation across spatial gradients, and stochastic changes in community composition owing to ecological drift vary within and across communities. Niche selection is hypothesized to increase beta-diversity when functional traits are strongly filtered from the regional species pool. However, the degree to which niche selection drives beta-diversity may depend not only on how interspecific trait variation influences environmental filtering from the species pool, but how intraspecific trait variation (ITV) influences niche selection across environmental gradients. In this study, we tested the hypothesis that ITV influences the relative importance of dispersal, drift, and selection on patterns of beta-diversity. We compared taxonomic beta-diversity and functional beta-diversity of understory woody plants across environmental and spatial gradients in a 20-ha temperate forest dynamics plot in the Missouri Ozarks, USA. Using five key traits (leaf size, SLA, leaf water content, leaf toughness and chlorophyll content), we tested the prediction that environmental gradients would explain more variation in functional beta-diversity that incorporates ITV relative to taxonomic beta-diversity.
Results/Conclusions
Taxonomic beta-diversity was higher than functional beta-diversity, suggesting functional redundancy among species in local communities. We found that a greater proportion of functional beta-diversity was explained by environmental variation than for taxonomic beta-diversity, suggesting an important role for trait filtering from the regional species pool. However, although ITV increased the total proportion of variation explained by environmental and spatial variables, the proportion explained by environmental variables was similar between taxonomic beta-diversity and functional beta-diversity that incorporates ITV. This result suggests that beta-diversity is influenced by spatial aggregation of traits within species, a pattern that could reflect an important influence of dispersal limitation during the assembly of understory plant communities. We highlight the utility of integrating ITV into studies of beta-diversity to help disentangle multiple drivers of community assembly.