PARENT SESSION
Poster Session #51: Rare, Threatened, and Endangered Species.
Friday, August 10, 2001. Presentation from 10:30 AM to 12:00 PM. Exhibition Hall

The influence of population size and density on pollinator service in Agalinis skinneriana.

Artiomow, Hannelore¹, Karron, Jeffrey¹, ¹

ABSTRACT- This is the first year of a two-year study on the pollination ecology of Agalinis skinneriana (Scrophulariaceae), a rare, hemiparasitic annual that is a habitat specialist found in the early successional habitats of hill and sand prairies. Agalinis skinneriana attracts generalist pollinators, including syrphid flies, small solitary bees, bumble bees and honey bees. The goal of this research is to determine whether population size and / or population density influence levels of pollinator service and seed set. Three paired large and small populations in southwest Wisconsin were selected for study. Two dense region and two sparse region pollinator observation plots were placed in each population. One pair of populations was observed each sampling day, with 20 minute observations at each plot. Pollinator visits were found to be significantly different between large and small populations (ss=0.457, df=1, P= 0.020), with small populations receiving more pollinator visitation per flower per hour than large populations. Dense regions within large populations received the fewest visits per flower, with less than one visit per hour. This contrasts with several other pollinator service studies. Local pollinator abundance is likely to be the limiting factor in pollinator visitation rates in A. skinneriana with the primary pollinators being small native bees and syrphid flies. There were more flowers per pollinator in large populations than in small populations.

KEY WORDS: Agalinis skinneriana, pollination ecology, population size, population density