An experimental test of the effect of plant functional group diversity on arthropod diversity

Characteristics used to categorize plant species into functional groups for their effects on ecosystem functioning may also be relevant to higher trop hic levels. In addition, plant and consumer diversity should be positively related because more diverse plant communities offer a greater variety of r esources for the consumers. Thus, the Functional group composition and rich ness of a plant community may affect the composition and diversity of the h erbivores and even higher trophic levels associated with that community. We tested this hypothesis by sampling arthropods with a Vacuum sampler (34531 individuals of 494 species) from an experiment in which we manipulated pla nt Functional group richness and composition. Plant manipulations included all combinations of three functional groups (forbs, C-3 graminoids, and C-4 graminoids) removed zero, one, or two at a time from grassland plots at Ce dar Creek Natural History Area. MN. Although total arthropod species richne ss was unrelated to plant Functional group richness or composition, the spe cies richness of some arthropod orders was affected by plant Functional gro up composition. Two plant characteristics explained most of the effects of plant functional groups on arthropod species richness. Nutritional quality, a characteristi c related to ecosystem Functioning, and taxonomic diversity, a characterist ic not used to designate plant Functional groups, seemed to affect arthropo d species richness both directly and indirectly. Thus, plant functional gro ups designated For their effects on ecosystem processes will only be partia lly relevant to consumer diversity and abundance.