Date of Award

8-2010

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Ecology and Evolutionary Biology

Major Professor

Susan E. Riechert

Committee Members

Christine R. Boake, Todd M. Freeberg, Gordon M. Burghardt

Abstract

A basic tenet of social structure is the assumption that the benefits of cooperative behavior must outweigh its costs if sociality is to evolve. The temperate spider, Anelosimus studiosus, exhibits a social behavioral polymorphism: individuals may defend asocial nests against intrusion by conspecifics or cooperate with them in multi-female nests. I initiated my investigation into this system by examining the extent to which social behavior phenotype is correlated with other behavioral traits and whether these correlations had adaptive consequences (Chapter 1). Using field surveys and laboratory experiments, I compared the success of asocial and social individuals in encounters over contested prey and prospective mates (Chapters 2, 3, 4). I then considered whether these trait correlations possess explanatory power for population-level divergence in behavior (Chapter 5). My results indicate social tendency is phenotypically correlated with several other types of behavior (e.g., activity-level, aggressiveness towards prey, exploratory behavior). The observed linkage between social tendency and other behavioral traits imposes a number of non-intuitive costs and benefits to possessing the social phenotype (e.g., social females are disadvantaged in agonistic interactions, but are more attractive to prospective mates). Finally, I examined the phenotypic correlations among behavioral traits for 18 different populations of An. Studiosus. I find that within- and between-population trait correlations resemble one another. Thus social tendency may not be “free” to evolve independently from other behavioral traits.

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