PARENT SESSION
Tuesday, August 8, 1:30-5:00 pm
COS 31 - Invasive species II: invasibility of communities and species invasiveness
Ballroom A, Ballroom Level, Cook Convention Center
Presiders: R Smith and S Jose

The identity of dominant species, not evenness, affects invasion in experimental plant communities.

Emery, Sarah^*,1, Gross, Katherine¹, ¹ W.K. Kellogg Biological Station, Hickory Corners, MI

ABSTRACT- While there has been extensive interest in understanding the relationship between diversity and invasibility of communities, most studies have only focused on one component of diversity: species richness. Although the number of species can affect a community's invasibility, other aspects of diversity- including species identity and evenness- or abiotic factors that can covary with diversity- such as soil heterogeneity or site history- may be equally important. We designed a mesocosm experiment that controlled for soil heterogeneity and species richness while varying dominant species identity and abundance to explicitly test whether communities with high evenness are more resistant to invasion, and whether the identity of dominant species in communities can affect invasibility. The identity of the dominant species significantly affected establishment of invaders, but evenness was not very important in predicting invasion success. Using path analysis, we found light interception and plant community biomass to be key mechanisms that determined invasion success of seedlings. Nitrogen availability became important to the survival of invaders through the second year of the experiment. Further, the identity of the dominant species had direct effects on invasion, separate from the effects of light, biomass, and nitrogen. Specifically, greater abundance of Coreopsis lanceolata in the mesocosms reduced invasion, though the mechanism that underlies this species-level effect remains unclear.

Key words: community invasibility, invasion biology, grasslands