Tuesday, August 4, 2009: 2:10 PM
Grand Pavillion I, Hyatt
Background/Question/Methods Urban habitat fragmentation can contribute to a decrease in biodiversity in affected communities. Previous studies have demonstrated negative effects of such fragmentation on birds, insect pollinators and plants. Herbivorous insects, however have been less studied and we here report the results of a study of how grasshoppers respond to urban fragmentation in native grassland remnants in the Colorado Front Range. Grasshoppers are important members of these habitats, where they are the major group of insect herbivores, aid in nutrient cycling and serve as food resources for a variety of taxa. Our study asked whether species-area relationships (SAR) associated with habitat fragmentation apply to grasshoppers in urban settings. We also examined whether grasshopper life history characteristics correlated with any of the observed patterns and the degree of nested subset relationship exists within these communities.
Our study included 13 fragmentation sites in the Colorado Front Range, ranging in size from 0.8ha to 36ha, and spanning a range of three hundred and twenty kilometers. Each site was surrounded by an average of 75% urbanization, including housing, roads, and industrial buildings. During the summer of 2008, each site was sampled twice, once in June and once in July. Each fragment was sampled with a combination of sweep-netting and observational species counts. These methods allowed for the inclusion of both juvenile and adult grasshoppers. Proportional sampling techniques were utilized, with 3 150m transects at sites up to 10ha and 1 additional transect added for each additional 10ha.
Our study included 13 fragmentation sites in the Colorado Front Range, ranging in size from 0.8ha to 36ha, and spanning a range of three hundred and twenty kilometers. Each site was surrounded by an average of 75% urbanization, including housing, roads, and industrial buildings. During the summer of 2008, each site was sampled twice, once in June and once in July. Each fragment was sampled with a combination of sweep-netting and observational species counts. These methods allowed for the inclusion of both juvenile and adult grasshoppers. Proportional sampling techniques were utilized, with 3 150m transects at sites up to 10ha and 1 additional transect added for each additional 10ha.
Results/Conclusions Results indicate a strong positive SAR for grasshoppers in urban habitat fragments with larger areas containing larger numbers of species (n = 13, p = 0.0023). We also demonstrate differential responses based on food preference, a significant interaction between area and feeding type, differential response based on body size, and high values of nestedness indices.
