Thesis (Ph.D.)--University of California, San Francisco, 2009. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3308. Advisers: Michael T. McManus; Michael German.

Thesis (Ph.D.)--University of California, San Francisco, 2009. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3310. Adviser: Christian Vaisse.

Thesis (Ph.D.)--University of California, San Francisco, 2009. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3337. Advisers: Graeme W. Davis; Robert H. Edwards.

Thesis (M.S.)--University of California, San Francisco, 2009. / Source: Masters Abstracts International, Volume: 47-06, page: 3492. Advisers: John D.B. Featherstone; Ling Zhan.

Thesis (Ph. D.)--University OF MICHIGAN.

Thesis (Ph.D.)--Brown University, 2008. / Advisor : Mark F. Bear. Includes bibliographical references.

Thesis (Ph.D.)--Brown University, 2008. / Vita. Advisor : Albert E. Dahlberg. Includes bibliographical references.

Thesis (Ph.D.)--University of California, San Francisco, 2009. / Source: Dissertation Abstracts International, Volume: 70-04, Section: B, page: 2072. Adviser: Hiten D. Madhani.

<p> Life exists in complex environments, requiring organisms to have adaptive developmental strategies in order to survive. The nematode <i>Caenorhabditis elegans</i> has evolved a developmental polyphenism whereby it may arrest development in the dauer diapause state when environmental conditions are not suitable for reproductive growth. The relative simplicity of the <i>C. elegans</i> nervous system, together with its robust molecular and genetic tool set, make it an ideal system in which to study how environmental stimuli are sensed and integrated to drive developmental plasticity. Food availability, temperature and the presence of dauer pheromone each inform the dauer fate decision. I have taken molecular and genetic approaches to study the mechanism by which pheromone signals are transduced by <i> C. elegans</i> sensory neurons and also to understand how food and pheromone signals are integrated to drive an adaptive developmental choice. I have identified roles in dauer formation for the protein scaffold QUI-1, the rough endoplasmic reticulum protein MACO-1 and a putative Tau tubulin kinase, which we have named PHD-1. I have also identified a critical role for the calcium/calmodulin-dependent protein kinase 1 CMK-1 in encoding the food signal and integrating this information in the dauer fate decision. Furthermore, these studies have led to the previously unrecognized roles for the ASH and AWC neurons in the regulation of dauer formation.</p>

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.