PARENT SESSION
Oral Session #77: Aquatic Ecology: Food webs, invertebrates. Presiding: R.A. Washington-Allen.
Friday, August 10, 2001. 8:00 AM to 12:00 PM. Hall of Ideas H.

Habitat overlap of intraguild predators: temporal patterns and the role of spatial complexity.

Hampton, Stephanie¹, ¹

ABSTRACT- Spatial segregation is one mechanism by which functionally similar species may reduce conflict with each other and coexist. Notonectids are aggressive aquatic insect predators with overlapping diets and typically similar habitat preferences. I examined interactions of the notonectids Buenoa and Notonecta, to determine whether spatial segregation is the primary mechanism for coexistence. I hypothesized that Buenoa lives in lower quality habitat in the open water to avoid conflicts with Notonecta, found primarily among vegetation. Using field and laboratory experiments, I found that diets of Buenoa and Notonecta do not overlap as much as previously thought and that habitat preferences are not affected by the presence of the other genus. However, temporal variation was important; spatial overlap in experiments was greater at night, a phenomenon that may greatly increase conflict. Laboratory experiments confirmed that Notonecta feeds on Buenoa equally well in light and dark in both vegetated and open water. Field data could not corroborate the experimental result that notonectids overlap more at night, due to substantial behavioral variation from day to day. I concluded that notonectids have the potential for increased conflict at night, but that this potential is not always realized because of daily variation in factors such as activity of other predators or prey. Coexistence may thus be facilitated by natural daily variation, variety of prey, and individual behaviors that help Buenoa reduce predator encounters or avoid capture.

KEY WORDS: heterogeneity, predation, macroinvertebrates, fishless