Stochastic density-dependent colony budding as a predictor of Argentine ant spread rate
Graduation Date
2010
Document Type
Project
Program
Other
Program
Thesis (M.S.)--Humboldt State University, Environmental Systems, Mathematical Modeling, 2010
Committee Chair Name
Robert Van Kirk
Committee Chair Affiliation
HSU Faculty or Staff
Keywords
Linepithema humile, Density dependent, Argentine ant, Simulation model, Budding, Spread rate, Invasive, Ants, Mathematical model, Humboldt State University -- Theses -- Mathematical Modeling
Abstract
Invasive species have multi-faceted effects on ecosystems, ranging from direct influences caused by competition or predation, to indirect biodiversity impacts. The Argentine ant (Linepithema humile) is a renowned invasive arthropod appearing in many provinces around the world. This species' short-distance dispersal process, colony budding, is poorly understood. A stochastic computer simulation composed of a linear population demographics model and a random-walk movement model was created. The seasonality of L. humile's reproductive, behavioral, and structural dynamics (such as dry season expansion, wet season contraction) were included within the demographics and movement models. Analysis of simulation output using a statistical general linear model (GLM) showed that yearly spread rate d was predicted by two parameters: Beta, the queen count at which there was a 50% chance of emigration and the average monthly emigration distance, B (R^{2}= 99.86). The GLM showed that spread rate, d, increased significantly with B, the mean monthly emigration distance (p 0.001). After accounting for the effect of B, yearly spread rate depended negatively and significantly on the emigration parameter, Beta (p 0.001). The effect of B on d decreased as Beta got larger (p 0.001). With a lower queen emigration rate (high Beta) the expected monthly distance traveled had a lower effect on colony spread rate than when emigration rate is higher. As Beta ranged from 2 to 10, mean monthly emigration distances between 17 and 26 meters were required to produce the average annual colony expansion rate of about 107 m/yr reported in the literature. These monthly emigration distances were consistent with observed values, suggesting that the model successfully captured the dynamics of an expanding argentine ant colony. Model results suggest that colony spread rate increases as a result of two factors: 1) higher frequency of rare, long-distance dispersal events, and 2) greater persistence of newly established nests through the winter.
Recommended Citation
Batenhorst, Nicole Diane, "Stochastic density-dependent colony budding as a predictor of Argentine ant spread rate" (2010). Cal Poly Humboldt theses and projects. 2119.
https://digitalcommons.humboldt.edu/etd/2119
https://scholarworks.calstate.edu/concern/theses/mp48sg05r