Plant genotypic diversity and environmental stress interact to negatively affect arthropod community diversity
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Many studies have found positive relationships between plant diversity and arthropod communities, but the interactive effects of plant genetic diversity and environmental stress on arthropods are not well documented. In this study, we investigated the consequences of plant genotypic diversity, watering treatment, and its interaction for the ground-dwelling arthropod community in an experimental common garden of quaking aspen (Populus tremuloides Michx.). We found that varying plant genotypic diversity and watering treatment altered multivariate arthropod community composition and structure. Arthropod biodiversity and richness showed a distinct response to the plant diversity × watering treatment interaction, declining sharply in water-limited genotypic mixtures. Abundance of arthropod functional groups did not show any response to diversity or the plant diversity × watering treatment interaction, but varied in their response to watering treatment, with predator and detritivore abundance increasing and parasitoid abundance decreasing in well-watered blocks. Our results conflict with most previous studies, and suggest that environmental stress can substantially change the nature of the plant-arthropod diversity relationship. Additionally, we suggest that the plant-arthropod diversity relationship is dependent on the type of plant and arthropod species sampled, and that the association between tree diversity and ground-dwelling arthropods may be much different than more commonly studied grassland species and herbivorous arthropods.
KeywordsArthropod community Ground-dwelling arthropods Tree diversity Genotypic diversity Drought Water stress Pitfall trapping Aspen Populus tremuloides
Thanks to Mary Pendergast for assistance in the design and implementation of this study, Ryan Shaw for aspen root collection, the USFS Rocky Mountain Research Station for greenhouse space, and the Utah State University (USU) College of Natural Resources for common garden space. Thanks to Kennedy Rubert III for conducting chemical analyses, and M. Ernest, T. Evans, and the USU evolution reading group for comments on the manuscript. This work was funded by a graduate research grant and graduate fellowship from the USU Ecology Center to M. Kanaga; the Utah Agricultural Research Station, USFS Rocky Mountain Research Station, USDA UV Monitoring Program, USDA National Resources Conservation Service and USU VP for Research to R. Ryel; the USU Community University Research Initiative and ADVANCE Program to K. Mock; and NSF grant DEB-0344019 to R. Lindroth.
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