Plant diversity and ecosystem process rates in native vs. exotic
communities
The homogenization of the earth's biota is affecting nearly every region of the
earth. This homogenization is expected to increase due to increased movement
of people and goods between regions. Grasslands, which cover roughly 25% of
the planet, contain perhaps the most homogenized communities. Many exotic
grassland species have spread to become common or even the dominant species in
many grasslands. We are currently testing whether 1) species diversity is
lower in exotic communities compared to comparable native communities, and 2)
whether any reduction in diversity is caused by changes in species interactions
in mixture. Specifically, we are testing whether exotic communities have
reduced stabilizing or equalizing effects (Chesson 2000) compared to native
communities. Exotic
communities are predicted to have a higher amount of the selection effect and a
lower amount of complementary resource use than native communities. These
hypotheses are being tested with 9-species mixtures of paired exotic and native
communities. Native and exotic species are paired based on similar ecological
growth forms and phylogeny, and all species have are being compared between
mixtures and their corresponding monocultures.