Grantee Research Project Results
Distribution and Impacts of the Argentine Ant in the Western Cape Province, South AfricaEPA Grant Number: U915338
Title: Distribution and Impacts of the Argentine Ant in the Western Cape Province, South Africa
Investigators: Lach, Lori J.
Institution: Cornell University
EPA Project Officer: Broadway, Virginia
Project Period: January 1, 1998 through January 1, 2001
Project Amount: $101,540
RFA: STAR Graduate Fellowships (1998)
Research Category: Academic Fellowships , Ecological Indicators/Assessment/Restoration , Fellowship - Ecology and Ecosystems
The objective of this research project is to investigate the factors related to the distribution of the Argentine ant, Linepithema humile, in the southwestern Cape Province of South Africa, and to experimentally test the effect of the invasion on pollinators of the fynbos plant Protea nitida.Approach:
Using bait card surveys and pitfall traps, I will map the Argentine ant and native ant distributions in three reserves in the Western Cape Province that encompass a range of conditions with respect to native ant fauna, altitude, rainfall, and human disturbance. I also will measure or collect environmental data to characterize the habitat, including percent ground cover, nearest water source, altitude, aspect, soil type and moisture content, and parameters related to disturbance (e.g., presence of garbage, distance to the nearest road, and extent of invasion by nonnative vegetation). I will analyze the relative influence of these variables on the distribution of the Argentine ant through multivariate statistical analyses. By manipulating native and Argentine ant densities in matched plots with controls, I will assess the invasion rate of L. humile in the presence and absence of native ants. If biotic resistance is not a factor, L. humile will invade plots with or without native ants at a similar rate. A preliminary study suggested that Argentine ants are affecting the abundance of 10 potential pollinators of P. nitida, an obligate crosser. To determine if the ants are ultimately affecting seed set, I will exclude Argentine ants from one-half of the branches of infested trees, and compare seed set to the infested inflorescences. To determine the mechanism by which L. humile is having an effect (i.e., intereference, exploitation, or both), I will manipulate nectar loads for a subset of uninfested inflorescences, and compare pollinator behavior on infested flowers, uninfested flowers with reduced nectar, and uninfested, unmanipulated flowers.Supplemental Keywords:
fellowship, South Africa, Linepithema humile, Protea nitida, Argentine ant.