Unique arthropod communities on different host-plant genotypes results in greater arthropod diversity

Studies on the effect of plant-species diversity on various ecological processes has led to the study of the effects of plant- genetic diversityin the context of community genetics. Arthropoddiversity can increase with plant-species or plant- genetic diversity( Wimpet al. in Ecol Lett 7:776–780, 2004). Plant diversity effects can be difficult to separate from other ecological processes, for example, complementarity. We asked three basic questions: (1) Are arthropodcommunities unique on different host-plant genotypes? (2) Is arthropoddiversity greater when associated with greater plant- genetic diversity? (3) Are arthropodcommunities more closely associated with host- plant geneticsthan the plant neighborhood? We studied canopy arthropodson Populus fremontiitrees randomly planted in a common garden. All trees were planted in a homogeneous matrix, which helped to reduce P. fremontii neighborhood effects. One sample was comprised of few P. fremontii genotypes with many clones. A second sample was comprised of many P. fremontii genotypes with few clones. A second data set was used to examine the relationships between the arthropodcommunity with P. fremontii genetic composition and the neighborhood composition of the focal host plant. Unique arthropodcommunities were associated with different P. fremontii genotypes, and arthropodcommunity diversity was greater in the sample with greater P. fremontii genotypic diversity. Arthropodcommunity similarity was negatively correlated with P. fremontii genetic distance, but arthropodcommunity similarity was not related to the neighborhood of the P. fremontii host plant.