Research

I have broad interests in community ecology, predator/prey interactions, agricultural biodiversity and ecosystem services. I examine many seemingly disparate systems, but constantly evaluate context-dependent, environmental drivers of biological control of crop pests. And of course, there is plenty of room in applied study systems for basic discoveries. Here are the major themes of my research:


Omnivory, structural complexity,  and top-down control

seed-food-web.pngMost of the predators in agroecosystems are omnivores. Broad diets enable them to persist in highly disturbed environments where prey availability is not particularly stable.  That means the food webs in crop environments are thrillingly complex (to a trophic ecologist) or frustratingly unpredictable (to a farmer). Furthermore, structurally complex refuge habitat, like cover crops, changes the foraging behavior of many predatory insects! To top it all off, predator foraging patterns and refuge use are both shaped by fluctuating cycles of predation risk (after all, predatory insects are often prey themselves). I use seed-based food webs to examine how omnivores shift their diets in response to predation pressure (“the stress diet”), and how this in turn affects biological control services.


Mixed signals: environmental drivers of tri-trophic interactions

Recent work from a rapidly-growing field suggests that pest control may be improved by indirect plant defenses, particularly herbivore-induced plant volatiles (HIPVs), which predators and parasitoids use to locate prey. Growers need clear information about how these induced plant defenses may enhance biocontrol and protect yield, but we currently have limited knowledge of the agriculturally-relevant impacts of HIPVs on biocontrol in working farm systems. A main reason for this poor understanding is that volatile production is a complex process mediated by many interacting ecological and abiotic factors that impede our ability to predict HIPV function in dynamic agroecosystems. For example, the composition of induced volatile profiles can be altered by the herbivore community, soil nutrition, microbes, drought stress, temperature, and humidity. Because so many exogenous variables ‘muddy up’ indirect plant defenses, relatively few plant volatile experiments are performed in field environments. However, without evidence from the field in naturally-diverse systems, community-level consequences and applied implications of tri-trophic interactions remain unclear. We combine observational and experimental approaches to examine volatile-mediated predator-prey interactions across diverse field environments.

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Photos Megan Asche

 


Ecological predictors of predator community structure

 Predator communities that are both diverse and even (that is, not dominated by a single aggressive predator) lead to strong pest control in agroecosystems. However, environmental predictors that lead to evenly-structured predator communities must be identified so that growers can most efficiently harness their ecosystem services.  We are examining local site characteristics like cover crops and non-pest prey, along with landscape-level factors to learn how diverse and even predator communities assemble, and how to manage a farm environment to promote them.