DOES DIVERSITY BEGET DIVERSITY - A CASE-STUDY OF CROPS AND WEEDS

The ecological literature is ambiguous as to whether the initial diver sity of a plant community facilitates or deters the diversity of colon izing species. We experimentally planted annual crop species in monocu lture and polyculture, and examined the resulting weed communities. Th e species composition of weeds was similar among treatments, but the s pecies richness of weeds was significantly higher in the polycultures than in the monocultures. This supports the 'diversity begets diversit y' hypothesis. Environmental microheterogeneity, diversity promoters, and ecological equivalency do not seem able to explain the observed pa tterns.