XVI International Botanical Congess

It has long been recognised that a connection should exist between the closeness of phylogenetic relationships between species and the strength of competitive interactions in a community. Most theories of coexistence depend upon trait differences and predict competitive exclusion of identical species. Community composition should depend upon where in the phylogeny of plants ecologically crucial trait differences have evolved. We demonstrate non-random niche overlaps among meadow plants measured along hydrologically-defined axes, and then determine where in their phylogeny the niche structure in our communities originates. We test the hypothesis that niche overlap should be less than random expectation between congeneric species (indicating a basis for their coexistence), but greater than random expectation between higher taxa (indicating the existence of functional groups).