Tuesday, November 22, 2011
101 Stanley Thomas Hall
Tulane University (Uptown)
Refreshments will be served
Rosalyn Rael, Pacific Ecoinformatics and Computational Ecology (PEaCE) Lab, Berkeley, CA
Species abundance patterns and competition in a stochastic niche model
Species abundance distributions may reflect the dynamic processes that influence population growth rates, but how they do so is not yet well understood. Recent studies focus on the relative importance of two types of mechanisms: niche and neutral dynamics. Neutral dynamics are based on demographic stochasticity and immigration and niche dynamics are generated by trait differences that affect the fitnesses, or population growth rates, of competing species. One recent study showed that abundance patterns produced under niche and neutral dynamics are very similar, especially when diversity is high relative to the number of niches. In that recent study, species in separate niches (groups of similar species) were essentially non-interacting. To further investigate patterns of species abundance, we compare the different distributions arising from a stochastic Lotka-Volterra competition model in which all species interact with one another. This model generates neutral communities when competition does not depend on traits, and communities with niches when competition declines with trait distance. We find more substantial differences between species abundance distributions of these two types of communities than have been previously shown, suggesting that mechanisms that produce niches may also influence abundance patterns. In particular we show that including interactions between niches results in increased mean species abundance, and that fitness differences within a niche have a large affect on the abundance distributions as well.
Center for Computational Science, Stanley Thomas Hall 402, New Orleans, LA 70118 email@example.com