Poster Session # 21: Biogeography, Biodiversity, Populations, and Genetics.

Thursday, August 7 Presentation from 5:00 PM to 6:30 PM. SITCC Exhibit Hall B.

Effects of initial conditions and resource supply on species assemblage dyamics: A microcosm study.

Mellard, Jarad*,1, Foster, Bryan1, 1 University of Kansas, Lawrence, KS

ABSTRACT- Community assembly theory predicts that initial conditions, invasion sequences, and priority effects are important in regulating the development of communities. An important goal in ecology is to isolate the ways in which historical processes and deterministic mechanisms (competitive dominance, species traits etc.) may influence communities of interacting species. We present results from the first year of a plant microcosm experiment designed to isolate the role of initial conditions (initial species abundances) on multispecies interactions and development of community structure. Initial relative abundances of eight grassland species were manipulated at two levels of nutrient supply to assess: (1) the degree to which assemblage dynamics are affected by initial conditions versus deterministic effects of particular species; and (2) how nutrient availability may alter the effects of initial conditions on assemblage dynamics. Abundance distributions at the end of the first growing season strongly reflected initial conditions, but also exhibited the dominant effects of two highly competitive species. Seedling growth rate was a good predictor of a species relative abundance in some treatments at the end of the first growing season. Resource levels interacted with initial conditions and species-specific effects to influence community states by altering the abundance hierarchy. Preliminary results indicate that: (1) both initial conditions and species-specific traits can interact in complex ways to regulate community development; and (2) the nature of these complex interactions may be modified substantially by resource availability.

Key words: initial conditions, competition, community assembly, resource supply