The Relation of Foraging Activity and Reproductive Success in Red Harvester Ant Colonies

Stanford University, Stanford CA

Investigators

Abstract

Deborah M. Gordon Proposal 0718631 The relation of foraging activity and reproductive success in red harvester ant colonies A fundamental question in behavioral ecology is how natural selection is shaping behavior. To answer this we need to know whether individuals that behave in a certain way are more likely to reproduce. The project continues a 25-year study of a population of about 350 red harvester ant colonies in southeastern Arizona. This is the longest-term behavioral and demographic study of any social insect population. Previous work shows that colonies compete for food, so foraging behavior should be important for colony survival and reproduction. The study will examine whether colonies that regulate foraging more effectively are more successful in reproducing. In social insects, colonies are the reproductive individuals, and it is notoriously difficult to measure the reproductive success of colonies. Genetic tools are needed to identify parent-offspring pairs. This is feasible only in a population in which a large sample of individual colonies can be followed throughout their life cycles. The proposed work will draw on unique long-term data and genetic markers. This will be an innovative application of genetic methods to develop a new measure of the reproductive success of social insect colonies. Social insect behavior raises intriguing questions because colonies operate without central control. Individual workers make decisions, using local information, that in the aggregate produce the coordinated behavior of the colony. Previous work shows that the regulation of foraging behavior depends on a network of interactions between workers. Combining behavioral measures of foraging activity with data on the reproductive success of known, individual colonies, this project will ask whether better foraging leads to higher reproductive success. This will make it possible to discover how natural selection is currently shaping the organization of ant colonies. The work will provide extensive laboratory and field research opportunities for undergraduate and graduate students, including women and minorities. The results will be incorporated into the PI''s outreach activities, including writing and speaking for the general public, and volunteer work in local schools. This long-term project now provides the most substantial demographic data on any social insect population, which will be available to people interested in using it.