PARENT SESSION
Oral Session # 53: Herbivory IV: Communities, Populations, and Genetics.
Presiding: JA Rudgers
Wednesday, August 6. 1:30 PM to 5:00 PM, SITCC Meeting Room 103.
Community genetics: The importance of genetic and environmental variation in affecting arthropod community composition on Oenothera biennis.
Johnson, Marc*,1, Agrawal, Anurag1, 1 University of Toronto, Toronto, Ontario, Canada
ABSTRACT- Genetic and environmental influences on plant resistance are well known to affect insect populations, but their effects on arthropod community composition are not well understood. We tested how plant genotype interacts with the environment at two spatial scales to affect herbivory, arthropod diversity (Simpson's D), species richness, and species abundance. We grew 14 clonal families of Oenothera biennis in each of five common gardens in sourthern Ontario. Each garden represented a unique habitat of O. biennis , and spatial blocks within gardens were created to examine environmental variation within habitats. All arthropod species on plants were identified and counted every 2-4 weeks during the summer. The amount of plant damage by early season herbivores varied nearly 2-fold between clonal families, but the effects of plant family were dependent on environmental variation within habitats. Plant family also affected arthropod diversity, species richness and abundance on individual plants, but in all cases, the effects of family were dependent on the habitat in which plants grew. Species richness and abundance varied by as much as 140% and 280%, respectively, between clonal families within a garden, but genetic variation affected herbivores more strongly than it did predators. Mean species richness was positively correlated (r = 0.68) with the proportion of plants within a clonal family that flowered. Plant genetic variation was frequently more important than within-habitat environmental variation in affecting arthropod community composition. At larger scales, however, variation between habitats was the most important factor. These results demonstrate that intraspecific genetic variation in plants has large ecological consequences for arthropod communities, but its influence decreases with increasing geographic scale.
Key words: herbivory, resistance, plant-insect, diversity