Sigma Xi Grant Proposal

The Roles of Natural and Semi-Natural Habitats in the Biodiversity of Beneficial Insects in Agricultural Landscapes.

Increased demands for food, livestock and biofuels have led to agricultural intensification and reductions in natural and semi-natural habitats that provide plant pollinators and natural enemies of insect pests with nectar, prey, and nesting resources. Connectivity between natural habitats in agricultural landscapes is thought to enhance the diversity of beneficial insects. Land-use practices that retain natural and semi-natural habitats may therefore support a high species diversity and abundance of beneficial insects, and the ecosystem services they provide.

Species diversity is important to community recovery following a disturbance (i.e., planting, spraying, or harvesting), especially for beneficial insects with limited dispersal abilities. Natural and semi-natural habitats provide structural complexity that supports larger populations and higher between-patch (beta) diversity of beneficial insects. Beta diversity provides “insurance” that the loss of function with a decline of one species will be replaced by a functionally similar species, therefore buffering against agricultural disturbance. In the Midwest US, marginal lands planted with perennial vegetation under the USDA Conservation Reserve Program (CRP) may provide important ecosystem services beyond erosion control and wildlife habitat. My proposed research will examine whether these ecosystem services also include a diversity of beneficial insects.

I will test three hypotheses: (1) the size and connectivity of semi-natural CRP habitats determines the within-patch (alpha) diversity and between-patch (beta) diversity of pollinators and natural enemies, with larger, more connected areas; (2) the relative amount of intensive (row crops) and extensive (pastures/meadows) land uses will influence the diversity, abundance, and species composition of beneficial insects; and (3) CRP plantings with warm season vs. cool season grasses affects the diversity of beneficial insects. I predict landscapes with larger, more connected natural and semi-natural habitats will have higher alpha and beta diversity of beneficial insects, and that native warm-season plantings will support a higher diversity of beneficial than cool-season grasslands.

My research will focus CRP habitats at 20 locations in 30 km2 of southwest OH. Sites are 2-20 ha in size and planted in either cool- or warm-season grasses and forbs. At each site, 3 x 5 grids of combined flight intercept/pan traps will be used to sample beneficial insects. Pollard walks will be used to estimate butterfly diversity, and transects will be used to sample plant species composition and flower availability. Trap samples will be sorted into bees (Apidae), flower visiting flies (Syrphidae and Calliphoridae), generalist predators (spiders, beetles, and true bugs), and parasitic Hymenoptera. Digital orthophotos, Landsat imagery, and GIS will be used to quantify the size and arrangement of surrounding land-use types at several radial distances around each site. I will use general linear mixed models and multivariate ordinations to determine how the species richness and abundance of pollinators and natural enemies vary with plant species composition, habitat area and connectivity of CRP land, and surrounding land uses.

My study will increase our understanding of the ecosystem services provided by semi-natural areas in agricultural landscapes, and inform landowners and agencies (USDA – NRCS) on CRP of land-use practices that promote the abundance and diversity of beneficial insects.

References:
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