Biodiversity and invasion of species: the Patagonian steppe as a model ecosystem

P. FLOMBAUM; O. E. SALA

Memphis, Tennessee, USA

Congreso; 91st Annual Meeting of the Ecological Society of America; 2006

Human activities drive increased rates of species invasions in natural ecosystems, with some invasions resulting in dramatic economic losses. We tested the hypothesis that increasing levels of biodiversity in an ecosystem results in decreasing rates of species invasion. We used the Patagonian steppe as a model ecosystem to test this hypothesis because its low natural diversity allows for simple experimental manipulation. We generated a biodiversity gradient with a removal experiment using 6 species, which account for 95% of total plant biomass. We generated 1, 2, 4, and 6 species gradient by removing species and portions of individuals while maintaining total biomass per plot. We studied the effect of species richness on the process of recolonization by subdominant and dominant plant species. We found that increased species richness decreased cover of invasive species. The cover of dominant and subdominant species decreased 3.6 and 1.8 times respectively between the high and low diversity treatments. However, richness of invasive species was not affected by biodiversity. Our results suggest that the invasion of species was controlled by species richness. Biodiversity may have reduced the biomass of invasive species because less unused resources were available in the richest than in the poorest end of the biodiversity gradient. However, biodiversity did not control the richness of invasive species because seedling establishment may not have been constrained by soil-resource availability.