PARENT SESSION
Contributed Oral Session 137: Agroecology: Pest Control, Dispersal, and Pollination
Thursday, August 11, 1:30 PM - 5:00 PM, Meeting Room 519 A, Level 5, Palais des congrès de Montréal

Source-sink dynamics and the subsidized biological control of aphid pests.

Forbes, Andrew^*,1, Ives, Anthony¹, ¹ University of Wisconsin-Madison, Madison, WI

ABSTRACT- Habitat heterogeneity can lead to source-sink dynamics, in which a species has a positive population growth rate in one habitat and a negative population growth rate in another. For ladybird beetles (Coleoptera: Coccinellidae) preying on aphids in agroecosystems, some species reproduce well in some crops while other species reproduce well in other crops. Experiments in field mesocosms illustrate that the ladybird Coccinella septempunctata fares better in alfalfa than soybeans, while the opposite is true for Harmonia axyridis. Previous field and mesocosm level studies on surviorship, population dynamics and movement, ongoing research on prey-specific ladybeetle development and a regional-scale observational study combine to show that both species are important for controlling aphid pests in both soybean and alfalfa crops. Therefore, each crop is subsidizing the biocontrol of aphids in the other crop, increasing the overall effect of biocontrol on pest suppression. Evidence to date points to the multi-scale nature of this subsidy occurring in the ladybeetle-aphid study system.

Key words: biological control, predator-prey dynamics, metapopulations