Sponsored Projects for Undergraduate Research

Argentine ants (Linepithema humile) are globally widespread invasive ants that form tremendous colonies that can span hundreds of miles, or even across continents, and contain billions of individuals. These “supercolonies” have very low aggression between colony members, which keeps intracolonial mortality low. Moreover, while many ant colonies only have a single queen with tens of thousands of workers, Argentine ants typically have 10+ queens per 1000 workers, allowing them to produce many more workers than an average ant colony. However, each year after the cold winter months (overwintering) the workers will execute ~90% of their queens and then begin to rear new replacement queens from the existing larvae. Executed queens make up ~8% of the colony biomass, but despite this being a large drain on colony resources we have very little understanding of what triggers the executions, how queens are selected for execution, and what factors are involved in producing new queens. With this research, I seek to answer the question: “What are the factors leading to queen executions and new queen production in Argentine ants?”

The Tsutsui lab has a long history of researching the dynamics of the Argentine ant society and this project aims to expand that expertise into the realm of queen turnover. Given that a colony may have hundreds or thousands of queens, most workers are not closely related to most queens. Since workers are sterile, their only option to gain fitness is to help their queen sisters survive and reproduce. The queen execution and new queen production provide a potential route for workers to selectively kill or rear queens to maximize their relatives’ fitness. The main method for this research will involve artificially overwintering Argentine ants and observing queen executions and new queen production. By altering the composition of these colonies (e.g. combinations of overwintered and non-overwintered queens, workers, and larvae) we can assess the importance of various factors on queen executions and new queen development. We can also manipulate the colonies to alter relatedness (combine queens, workers, and larvae from distant collection sites) to determine how workers select who lives and dies.