PARENT SESSION
Monday, August 7, 5:00-6:30 pm
Poster Session 2 - Invasive species
Exhibit Hall, Ballroom Level, Cook Convention Center

From 'the rich get richer' to biotic resistance: variable relationships between diversity and invasibility.

Evans, Jeffrey^*,1, Landis, Douglas¹, Schemske, Douglas¹, ¹ Michigan State University, East Lansing, MI

ABSTRACT- The influence of species diversity on community invasibility is variably argued to be positive, neutral, or negative. In eight temperate deciduous forests in Southern Michigan that have been invaded by exotic plant species, we found a positive correlation between site native species richness and site exotic species richness. However, the relationship between exotic plant abundance and species richness within sites changed predictably from positive at species poor sites to negative at species rich sites, implying that different mechanisms are responsible for either promoting or resisting invasions in different communities. We propose that environmental stress tolerance may contribute to limiting invasions in species poor assemblages, whereas competitive interactions are more likely to limit invasions in species rich communities. This suggests that neither biotic resistance nor 'the rich get richer' hypothesis satisfactorily explains patterns of invasibility. Rather, both serve as endpoints along a continuous gradient of resource competition and environmental stress tolerance.

Key words: invasibility, diversity, invasive plant species