Investigation of a Brood Fostering Hypothesis that Explains Variation in Levels of Sociality

University Of Tennessee Knoxville, Knoxville TN

Investigators

Abstract

Investigation of a Brood Fostering Hypothesis that Explains Variation in Levels of Sociality Susan E. Riechert & Thomas C. Jones The exhibition of altruistic and cooperative behavior in a world, which favors individualism and selfishness is a problem that has been approached through the study of bee, wasp and ant social systems. The social insects, however, possess a unique mechanism of inheritance (haplodiploidy) that makes self-sacrifice easier to achieve than in other systems. Spiders make a better model for investigation of the determinants of social behavior as they have the typical diploid pattern of inheritance. This study involves the analysis of the factors underlying cooperative brood care in a spider that exhibits a higher incidence of multiple female colonies caring for a common brood at higher latitudes. A mathematical model indicates that females will cooperatively care for a brood in those environments in which a single female has a high probability of dying before her offspring are able to care for themselves. A series of field measures and experiments will be completed along a latitudinal gradient to quantify the effect of cooperation on reproductive success under different environmental conditions. Breeding experiments and molecular genetics analyses will also be completed to examine the degree to which cooperative behavior is flexible and to learn whether cooperating individuals are relatives.