Regulate Pea Aphid Populations in Alfalfa?
A Model-based Approach to Analyzing Ecological Time Series.
University of Wisconsin-Madison
E202 Engineering Building
In southern Wisconsin, pea aphid (Acyrthosiphon pisum) populations
are regularly held in check below economic threshold. Cage
experiments and ecological theory suggest that this regulation
is most likely biological control by the parasitoid wasp Aphidius
ervi. However, it is difficult to draw inferences about
dynamics at the scale of a field on the basis of small-scale experiments,
and additional mechanisms may be more important at larger scales
(e.g., predation, host-plant interactions). Here, I present
a model-based method for analyzing monitoring data from four alfalfa
fields that attempts to separate the effect of parasitoids from
the other determinants of aphid dynamics at the scale of the field.
The model is constructed in a way that allows the data to determine
the functional relationship between parasitism rate and aphid
density, a relationship is key to understanding host-parasitoid
dynamics. Although the model is developed explicitly in
the context of aphids and parasitoids, the general framework could
be applied to a number of ecological systems where investigators
seek to analyze time series data from monitoring studies.
Refreshments will be served at 3:45 p.m. in Room 008 of the Statistics