Evolutionary genetics of gall-forming aphids: Population and behavioral processes

Persistent Link:
http://hdl.handle.net/10150/279854
Title:
Evolutionary genetics of gall-forming aphids: Population and behavioral processes
Author:
Abbot, Douglas Kilpatrick
Issue Date:
2001
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
I investigated patterns of genetic variation in the North American gall-forming aphid, Pemphigus obesinymphae. In Chapters 2a and 2b, I developed and then implemented clone-specific molecular markers to investigate clonal mixing in P. obesinymphae . During its gall-forming phase, P. obesinymphae clones produce aggressive larval "soldiers", which altruistically defend their colonies from natural enemies. I showed that movement occurs between galls, indicating that P. obesinymphae colonies are not pure clones. I also showed that intruders behave selfishly, by not defending unrelated clones, and by accelerating development into reproductive adults. These results reveal a greater degree of complexity and conflict in aphid social groups than previously known. In Chapter 2c, I surveyed molecular variation in P. obesinymphae and its bacterial endosymbiont, Buchnera aphidicola. I found levels of variation at two Buchnera loci to be similar to those estimated from a previous study on a distantly-related aphid, Uroleucon ambrosiae. In the western US, P. obesinymphae and B. aphidicola were nearly monomorphic, and in the eastern US, estimates of synonymous divergence ranged from 0.08 to 0.16%. Most polymorphisms in sub-populations at low frequencies, indicating a recent purge of ancestral polymorphism. These results emphasize the importance of aphid population biology in shaping evolutionary patterns in B. aphidicola. In Chapter 2d, I explored the role of life cycle variation in speciation between Pemphigus aphids. P. obesinymphae and P. populi-transversus are closely-related and sympatric on the cottonwood, Populus deltoides (Salicaceae), but they have distinctly different life cycles. P. populi-transversus has a sexual stage that occurs in the fall, while P. obesinymphae produces sexuales in late spring. Field evidence indicates that intermediate phenotypes rarely occur, and mitochondrial and bacterial endosymbiont DNA sequences show no maternal gene flow between the two species. I considered the possibility of an initial allopatric phase in the divergence, and discuss the sequence of evolutionary changes that likely led to the sympatric divergence of P. populi-transversus and P. obesinymphae. The most plausible interpretation of available data is that a shift in timing of the life cycle in an ancestral population spurred divergence between the species pair.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Biology, Ecology.; Biology, Entomology.; Biology, Genetics.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Ecology and Evolutionary Biology
Degree Grantor:
University of Arizona
Advisor:
Moran, Nancy

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleEvolutionary genetics of gall-forming aphids: Population and behavioral processesen_US
dc.creatorAbbot, Douglas Kilpatricken_US
dc.contributor.authorAbbot, Douglas Kilpatricken_US
dc.date.issued2001en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractI investigated patterns of genetic variation in the North American gall-forming aphid, Pemphigus obesinymphae. In Chapters 2a and 2b, I developed and then implemented clone-specific molecular markers to investigate clonal mixing in P. obesinymphae . During its gall-forming phase, P. obesinymphae clones produce aggressive larval "soldiers", which altruistically defend their colonies from natural enemies. I showed that movement occurs between galls, indicating that P. obesinymphae colonies are not pure clones. I also showed that intruders behave selfishly, by not defending unrelated clones, and by accelerating development into reproductive adults. These results reveal a greater degree of complexity and conflict in aphid social groups than previously known. In Chapter 2c, I surveyed molecular variation in P. obesinymphae and its bacterial endosymbiont, Buchnera aphidicola. I found levels of variation at two Buchnera loci to be similar to those estimated from a previous study on a distantly-related aphid, Uroleucon ambrosiae. In the western US, P. obesinymphae and B. aphidicola were nearly monomorphic, and in the eastern US, estimates of synonymous divergence ranged from 0.08 to 0.16%. Most polymorphisms in sub-populations at low frequencies, indicating a recent purge of ancestral polymorphism. These results emphasize the importance of aphid population biology in shaping evolutionary patterns in B. aphidicola. In Chapter 2d, I explored the role of life cycle variation in speciation between Pemphigus aphids. P. obesinymphae and P. populi-transversus are closely-related and sympatric on the cottonwood, Populus deltoides (Salicaceae), but they have distinctly different life cycles. P. populi-transversus has a sexual stage that occurs in the fall, while P. obesinymphae produces sexuales in late spring. Field evidence indicates that intermediate phenotypes rarely occur, and mitochondrial and bacterial endosymbiont DNA sequences show no maternal gene flow between the two species. I considered the possibility of an initial allopatric phase in the divergence, and discuss the sequence of evolutionary changes that likely led to the sympatric divergence of P. populi-transversus and P. obesinymphae. The most plausible interpretation of available data is that a shift in timing of the life cycle in an ancestral population spurred divergence between the species pair.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectBiology, Ecology.en_US
dc.subjectBiology, Entomology.en_US
dc.subjectBiology, Genetics.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineEcology and Evolutionary Biologyen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorMoran, Nancyen_US
dc.identifier.proquest3031359en_US
dc.identifier.bibrecord.b42283358en_US
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