Annette Ostling fra University of Michigan besøger CMEC – University of Copenhagen

23. september 2010

Annette Ostling fra University of Michigan besøger CMEC

Annette vil holde møder med medlemmer af centeret og afholde et sektionsseminar:  

Demographic complexity and the neutral theory of ecology

Foredragholders adresse: University of Michigan
Tid: Fredag 24. september kl. 14.00
Sted: Auditorium A, Universitetsparken 15
Vært: Carsten Rahbek

Do competing species coexist in communities because of niche differences, or because of similarities? Classical ecological theory has focused on niche differences and the stabilizing mechanisms they provide. More recently, the neutral theory of community ecology posits that competing species may in many cases coexist through similar fitness in a given environment. In that case community structure is shaped primarily by demographic stochasticity and dispersal limitation. But to make quantitative testable predictions from this theory, ecologists have been using models that, in order to be tractable, take more simplifying assumptions than just equal fitness of species. In particular, most predictions are based on models that assume identical demographic rates (i.e. birth and death rates) for all individuals in the community. Real communities have much more demographic complexity, even if species are equal in fitness in a given environment. Some of neutral theory's predictions are likely sensitive to these additional simplifying assumptions. Hence it is unclear if agreement with these predictions is an indication of neutral community dynamics, nor if departures from them are evidence for niche differences. In this talk I will demonstrate the influence of two types of demographic complexity on the structure of communities produced by neutral models: a fitness-equalizing tradeoff in birth and death rates across species, and size structured demographic rates. In particular, I will show preliminary results of fitting a size-structured neutral model to a tropical forest data set. I will end by discussing how neutral theory might be useful to ecologists as a testable null model of community assembly, despite the sensitivity of its predictions to demographic complexity and parameter uncertainty.