1. Food webs at the landscape scale
My research in this area focuses on understanding how “space” influences the dynamics of arthropod food webs. In particular, I am interested in how movement of organisms in the landscape affects trophic interactions. This approach involves the explicit recognition that ecosystems are not closed and that matter, energy and organisms flow across their boundaries. My research is aimed at understanding the factors that affect the magnitude and direction of these ecological flows and what are the ultimate consequences for the donor and recipient systems.
Research Projects
Conservation Biological Control
Ben Werling has been working with Wisconsin potato growers in order to understand how within-farm and among-farm (landscape) variables influence the diversity and abundance of natural enemies in agroecosystems. This research tests a basic tenet of conservation biological control that natural enemies within a crop are affected by habitat variables outside of a crop. We have been focusing on “semi-natural” (perennial) areas within agroecosystems as potential reservoirs for beneficial insects and how the abundance of non-agricultural lands within the broader landscape influences beneficial insects. Joe Kaser is examining the temporal spread of potato pests within agricultural landscapes.
Satellite image of Central Wisconsin showing high-intensity agricultural areas (left side) and low-intensity (“extensive”) agricultural areas (right)
Native plant species studied for attractiveness to beneficial insects (Photos Ashley Bennett)
Arthropod movement within agroecosystems
This collaborative project with Katie Forbes was aimed at determining the temporal and spatial dynamics of feeding of the exotic biological control agent, Harmonia axyridis. We developed a stable isotope approach that examined δ13C ratios in different body parts to understand the historical diets of the predator. We determined that soybean habitats were significant sources of ladybeetle late in the season. Moreover, sampling across the landscape found that H. axyridis has a more variable diet than other ladybeetles common in agroecosystems, suggesting that these predators are highly mobile [publication].
Dissection of Harmonia axyridis for δ13C analysis. (Photo Claudio Gratton)
Spatial subsidies at the lake-land interface
This project examines the role that aquatic resource subsidies play in terrestrial ecosystems. Recent empirical and theoretical models indicate that the dynamics within food webs are often influenced by resources coming from outside of the focal food web. Jack Donaldson and Nate Tull are examining how large-scale and temporally pulsed (cyclic) midge emergences from a lake in northern Iceland (Myvatn) affect terrestrial arthropod food webs. The cyclic nature of the spatial subsidy allows us to examine the persistence of a resource within a terrestrial system as it influences both plant resources and consumers.
Lake Myvatn (“Midge Lake”) in northern Iceland. Cage excluders for manipulating predators can be seen along shore. (Photo Jack Donaldson)
Effect of invasive species on native communities
My previous work before coming to Wisconsin included studies of how invasive plants of wetlands influences native arthropod assemblages. Here in Wisconsin, I studied a recent association between a native silk moth and invasive plant. I showed that although previously undocumented, the native “Bog Buckmoth” (deemed of conservation concern in some Great Lakes states), can successfully develop on Purple loosestrife (though at a cost) and significantly reduce seed production [publication link].
Lythrum salicaria (left) and a late-instar caterpillar of the native Bog-buckmoth (Hemileuca sp., right, Saturniidae). (Photos Claudio Gratton)
My active research in this area is now centered on understanding potential non-target effects of planned biological control releases. In a multi-state project, we are developing a classical biological control program to control the soybean aphid (Aphis glycines). Our working group specifically is analyzing the potential risks of natural enemy releases to non-target aphids.