PARENT SESSION
Poster Session 39: Late Breaking and Newsworthy Posters
Friday, August 12, 8:30 AM - 10:30 AM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal

The guild character model in exploitatively competing communities: Its application to biodiversity-ecosystem function relationships.

Tanaka, Yoshinari^*,1, ¹ Chuo University, Hachioji, Tokyo, Japan

ABSTRACT- As one of the first step to aggregately describe community dynamics in a complex food web, a simplified exploitative competition model is presented. The model summarizes composite species into two variates, i.e., phenotypic distribution within a guild (functional group) and its total biomass. The phenotype, which characterizes performance, e.g., resource utilization, of individuals of a species , composite species, and the whole guild, is called as guild character. Changes in the distribution (or moments) of the guild character correspond to changes in the species composition (or relative abundances) and partly to evolutionary changes in composite species, both of which follow changes in distribution of resources. The rate of changes in mean and variance of a guild character is the covariance between intrinsic rates of natural increase and means or squared deviations of phenotypes among the composite species. Based on the guild character model applied to an exploitatively competing community, community responses to temporal environmental changes in the resource distribution are formulated. The community response in terms of the rate of change in mean guild character is determined by the range of the guild character, but is independent of the relative abundance of composite species, competition coefficients between species, and the number of species in a guild. Since the mean guild character (or higher moments of the guild character) always responds in a direction to maximize the resource utilization by the community, the community response may represent the ability of a community to maintain the ecosystem function to temporal changes in environments. The present result that the community response depends largely on the range of the guild character highlights the importance of rare and unusual (phenotypically deviant) species in the maintenance of ecosystem functions under changing environments, and present an alternative interpretation of the insurance hypothesis by discarding the concept of narrow-sense biodiversity, which is defined as the number of species regardless of phenotypes.

Key words: resource competition, quantitative character, ecosystem function, environmental change