PARENT SESSION
Symposium #7: Paradigms lost: Theory change in ecology.

Organized by: K Cudddington and B Beisner
Monday, August 5. 1:00 PM to 3:45 PM. Leo Rich Theatre.

A new theory of community assembly: From Elton and Hutchinson to now.

TILMAN, DAVID^*,1, ¹ University of Minnesota, St. Paul, MN

ABSTRACT- A new resource-based theory of community assembly explicitly predicts community composition, diversity and abundance patterns. In contrast to neutral theory of diversity and abundance, this theory also predicts the traits of abundant and rare species. This mechanistic extension of the niche-based concepts of Elton, Hutchinson and MacArthur uses classic resource-competition theory, with species or genotypes having tradeoffs in competitive abilities for limiting resources. Theory predicts that community assembly occurs because of differences in abilities of potential invaders to attain positive growth on resources left unconsumed by existing species. The chance of invasion is predicted to decline as diversity increases because of lower levels of unconsumed resources at higher diversity. Surprisingly, this theory predicts a limit to interspecific similarity. This limit structures diversity, composition and abundance patterns. This limit occurs because resource reduction by individual species greatly reduces the chance of invasion by species with similar requirements. Moreover, greater mortality during resource-dependent growth from seed or juvenile to adult broadens the limit to similarity, thus causing diversity to scale inversely with body size.

KEY WORDS: community assembly, limiting similarity, competition, neutral theory