This research utilizes aphids to address some of the emerging themes in social evolution. To begin to address these themes, I identified traits to measure sociality in aphids. I found that for the ecological and behavioural traits tested, housekeeping and defense, there were quantifiable differences between social and nonsocial species. However, there was no clear threshold that differentiated social from nonsocial species, meaning that definitions of sociality in aphids depend in part on the traits that are measured. Next, I explored a major theme of social evolution, the ability of groups to protect the nest from predators, by characterizing adaptations for defense. I found that aphid soldier elicit an overexpression of the melanization immune response in victims causing toxicity which leads to death, and successful defense of the nest. Finally, cooperation is inherently vulnerable to exploitation by cheaters. Aphids present a rare opportunity to study the effect of cheaters on groups due to multiple unique life history traits. I characterized the consequences of cheaters for weakly and nonsocial species and, contrary to our expectations, the presence of cheaters has the strongest negative effect on the nonsocial species, compared to the social or weakly social species. The results suggest that there is a more complex relationship between competition and relatedness than previously realized. Taken together, these results offers a new perspective on the role of defense, social immunity and kin selection in the evolution of sociality in this disparate group.
| Identifer | oai:union.ndltd.org:VANDERBILT/oai:VANDERBILTETD:etd-09222014-113956 |
| Date | 22 September 2014 |
| Creators | Lawson, Sarah Page |
| Contributors | Antonis Rokas, Julian Hillyer, Patrick Abbot, Jay Evans, Kenneth Catania |
| Publisher | VANDERBILT |
| Source Sets | Vanderbilt University Theses |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.vanderbilt.edu/available/etd-09222014-113956/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to Vanderbilt University or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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