COMMUNITY STRUCTURE IN SAND DUNE ANNUALS - IS SEED WEIGHT A KEY QUANTITY

1 Patterns of community structure in relation to seed weight are described for 2 There is a highly significant negative relationship between seed weight and proportional abundance within a community, where proportional abundance is the number of individuals of a particular species divided by the total number of individuals of all species recorded at a given study area. 3 Seed weight is also negatively related to average abundance in occupied quadrats and to the proportion of quadrats occupied. 4 Comparing absolute differences in seed weight it was found that common species have more similar seed weights than rare species. 5 The relationship between a species' seed weight and its dispersal and competitive ability are briefly reviewed. Based on published experimental studies it appears that large-seeded species are generally competitively superior to small-seeded ones. The implications of these patterns for the mechanisms structuring annual dune communities are discussed.