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- Member of: ASU Electronic Theses and Dissertations
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Description
A notable feature of advanced eusocial insect groups is a division of labor within the sterile worker caste. However, the physiological aspects underlying the differentiation of behavioral phenotypes are poorly understood in one of the most successful social taxa, the ants. By starting to understand the foundations on which social behaviors are built, it also becomes possible to better evaluate hypothetical explanations regarding the mechanisms behind the evolution of insect eusociality, such as the argument that the reproductive regulatory infrastructure of solitary ancestors was co-opted and modified to produce distinct castes. This dissertation provides new information regarding the internal factors that could underlie the division of labor observed in both founding queens and workers of Pogonomyrmex californicus ants, and shows that changes in task performance are correlated with differences in reproductive physiology in both castes. In queens and workers, foraging behavior is linked to elevated levels of the reproductively-associated juvenile hormone (JH), and, in workers, this behavioral change is accompanied by depressed levels of ecdysteroid hormones. In both castes, the transition to foraging is also associated with reduced ovarian activity. Further investigation shows that queens remain behaviorally plastic, even after worker emergence, but the association between JH and behavioral bias remains the same, suggesting that this hormone is an important component of behavioral development in these ants. In addition to these reproductive factors, treatment with an inhibitor of the nutrient-sensing pathway Target of Rapamycin (TOR) also causes queens to become biased towards foraging, suggesting an additional sensory component that could play an important role in division of labor. Overall, this work provides novel identification of the possible regulators behind ant division of labor, and suggests how reproductive physiology could play an important role in the evolution and regulation of non-reproductive social behaviors.
ContributorsDolezal, Adam G (Author) / Amdam, Gro V (Thesis advisor) / Brent, Colin S. (Committee member) / Gadau, Juergen (Committee member) / Hoelldobler, Bert (Committee member) / Liebig, Juergen (Committee member) / Arizona State University (Publisher)
Created2012
Description
The gender gap of women in science is an important and unresolved issue in higher education and occupational opportunities. The present study was motivated by the fact that there are typically fewer females than males advancing in science, and therefore fewer female science instructor role models. This observation inspired the questions: Are female college students influenced in a positive way by female science teaching assistants (TAs), and if so how can their influence be measured? The study tested the hypothesis that female TAs act as role models for female students and thereby encourage interest and increase overall performance. To test this "role model" hypothesis, the reasoning ability and self-efficacy of a sample of 724 introductory college biology students were assessed at the beginning and end of the Spring 2010 semester. Achievement was measured by exams and course work. Performance of four randomly formed groups was compared: 1) female students with female TAs, 2) male students with female TAs, 3) female students with male TAs, and 4) male students with male TAs. Based on the role model hypothesis, female students with female TAs were predicted to perform better than female students with male TAs. However, group comparisons revealed similar performances across all four groups in achievement, reasoning ability and self-efficacy. The slight differences found between the four groups in student exam and coursework scores were not statistically significant. Therefore, the results did not support the role model hypothesis. Given that both lecture professors in the present study were males, and given that professors typically have more teaching experience, finer skills and knowledge of subject matter than do TAs, a future study that includes both female science professors and female TAs, may be more likely to find support for the hypothesis.
ContributorsEbert, Darilyn (Author) / Lawson, Anton (Thesis advisor) / Maienschein, Jane (Committee member) / Mustard, Julie (Committee member) / Arizona State University (Publisher)
Created2010