In this dissertation, the evolutionary and ecological determinants of host range of nematode parasites (Tylenchida: Allantonematidae: Howardula, Parasitylenchus) of mushroom-breeding Drosophila (Diptera: Drosophilidae) are examined. These nematodes are horizontally transmitted, obligate parasites, often with severe effects on host fitness. Phylogenetic analysis of Drosophila and Howardula DNA sequences shows little congruence between host and parasite phylogenies, with frequent host colonizations and losses. Drosophila -parasitic Howardula are not monophyletic, with host switches occurring between Drosophila and distantly related mycophagous sphaerocerid flies. Molecular analysis reveals eight new Howardula species. The ability of five nematode species to infect and develop in 24 taxonomically diverse Drosophila species is assessed. All nematode potential host ranges but one are large, even for host specialists. Novel hosts that are distantly related from the native host are less likely to be infected, but among closely related hosts there is variation in susceptibility. Potential host ranges differ greatly between related parasite species. Most novel infections do not cause reductions in host fecundity, with the exception of P. nearcticus. Thus, Drosophila-nematode associations are dynamic, and appear to be driven by a combination of repeated opportunities for host colonization due to shared mushroom breeding sites, and large nematode potential host ranges. Recent colonization of novel host species may explain the striking differences in virulence observed in natural Drosophila-nematode associations. For example, Nearctic species of the Drosophila testacea group are more severely affected by infection than Palearctic species, including complete female sterility. Cross-infection experiments reveal that virulence is evolutionarily labile in testacea-Howardula associations, and that high levels of virulence manifested in some host-parasite combinations are due to a lack of host resistance. Finally, ecological determinants of host range are considered. First, competition between a generalist and a specialist parasite of D. recens is assessed by comparing nematode infection success and reproduction in single and double infections. Second, differences between the actual and potential host ranges of Howardula neocosmis are documented. This parasite appears restricted to D. acutilabella in nature, yet successfully parasitizes the closely related, microsympatric D. cardini. Neither differential virulence nor competitive interactions between hosts explain the host range differences.

Sequestration of the blue biliprotein, insecticyanin, into developing oocytes of the hawkmoth, Manduca sexta was investigated using diverse techniques. Oudin's immunodiffusion assays revealed that insecticyanin concentration in mature eggs (29.6 μM) is slightly higher than that in hemolymph (25.8 μM). The endocytotic uptake of insecticyanin was visualized at the light microscopic level using autoradiography. Uptake of ¹²⁵I-insecticyanin by isolated oocytes was ligand specific, saturable with increasing insecticyanin concentration, and sensitive to parameters such as size of oocyte, constituents of media and temperature. Analysis of in vitro uptake data yielded values of K(uptake) (insecticyanin concentration at half-maximal uptake rate) of 4.2 μM and V(max) (maximum rate of uptake) of 1 pmol follicle⁻¹ h⁻¹. Oocyte membrane proteins were efficiently solubilized using 40 mM detergent CHAPS. Labeled insecticyanin was shown to bind to crude follicle membranes and solubilized membrane proteins with high specificity and affinity. The K(d) (equilibrium dissociation constant) was estimated as 40 nM and 17 nM for crude membranes and solubilized membrane proteins, respectively. The B(m) (maximum binding) estimated from crude membrane and solubilized membrane protein was 1.6 and 11.4 pmol/mg proteins respectively. Competition studies showed that binding of labeled insecticyanin to its receptor was blocked by an excess of unlabeled insecticyanin but not by other major hemolymph proteins, lipophorin and vitellogenin of M. sexta. Additional binding experiments demonstrated that receptors for insecticyanin are only present in oocyte membranes, not in fat body, gut tissue or ovariole. The results from co-immunoprecipitation showed that the apparent molecular mass for insecticyanin receptor is approximately 185 kDa on reducing SDS-PAGE gel while chemical crosslinking of the insecticyanin-receptor complex revealed a product with a molecular mass near 1000 kDa. This result suggests that the insecticyanin receptor has a multimeric structure, or that four receptor molecules can bind to one insecticyanin tetramer.

The evolution of wing morphology in three clades of Drosophila was investigated using a method of mapping a complex of continuous characters developed for landmark configurations. In the melanogaster subgroup, a rate test for morphological characters was applied using the mutation-drift equilibrium (MDE) model under a range of evolutionary scenarios. The results indicate that wing morphology has evolved at a slower rate than genital morphology. The rate test under the MDE model suggested that genital morphology has evolved at a neutral rate while wing morghology has been under stabilizing selection. In the cactophilic species of the repleta group endemic to the Sonoran desert, wings have evolved in response to two factors: adaptation to the density of rots in the host cacti and adaptation to Sonoran desert conditions. Aerodynamic parameters of the wing were calculated based on a steady-state aerodynamic model. Flies using larger host cacti tend to have wings of greater aspect ratio which are better suited for long range dispersal. Flies adapted to Sonoran desert conditions tend to have wings with broader bases and narrower tips, suggesting greater efficiency at fast forward flight. The evolution of wing pigmentation patterns in the Hawaiian picture-winged Drosophila was examined in a phylogenetic context. Four specific hypotheses were tested: (1) has the overall degree of pigmentation evolved from more lightly to more heavily pigmented wings; (2) has the evolution of pigmentation patterns proceeded through a process of elaboration resulting in patterns of greater complexity; (3) are the fundamental symmetries in pigmentation pattern the same for all species in this group; and (4) are the patterns of symmetry related to what is known about wing development in Drosophila melanogaster? The pattern of evolutionary changes in the level of pigmentation was not consistent with a hypothesis of gradual increase. Based on a measure of complexity derived from Shannon's information content, there is no compelling evidence to support the hypothesis of evolutionary elaboration of pattern. There is evidence for one major evolutionary shift in the pattern of symmetry. A model linking fundamental symmetries in pigmentation pattern to wing development is presented.

Plant-feeding insects are the most species-rich group on the planet today. Models have been proposed to explain this diversity, but few use the fossil record to evaluate hypotheses. I conduct studies in modern systems to examine (1) taphonomic biases in insect preservation and how this may affect our understanding of insect diversity trends through time and (2) patterns of herbivory in modern ecosystems to improve the comparability of fossil and modern datasets. I then use the Cenozoic fossil record to examine the history of ecological associations between insects and plants and how these interactions respond to environmental change. I conducted an actualistic study on the preservation of beetles in Willcox Playa, an ephemeral lake in SE Arizona. I compared the insect death assemblage in shoreline sediments to the living beetle assemblage. The sediments captured 56% of the live-collected beetle families, and 28% of the live-collected beetle genera. The relative abundances of living beetles were not reflected in the death assemblage. Beetle diet, feeding habitat, and size influenced the composition of the death assemblage. Necrophagous, ground-dwelling and smaller beetles were over-represented in the death assemblage. Such biases should be considered in insect paleoepology and in studies of diversity change. Annual variation in herbivory was compared within and between two lowland neotropical forests Costa Rica. Herbivory did not vary significantly within sites between years, but was significantly different: between sites. Modern herbivory data collected with discrete sampling techniques is compartable to herbivory data from fossil forests. Herbivory data from one-time collections of leaf litter are most suitable for comparison with fossil herbivory. I compared herbivory between two Eocene floras and between the Eocene floras and six modern floras. A decline in levels of herbivory corresponds with a decline in temperature from the middle to the late Eocene. Fossil herbivore damage was significantly lower than modern herbivore damage. This pattern may result from taphonomic bias, environmental differences between the fossil and modern sites or evolutionary change.

This work focused on how visual and olfactory cue use by insects affect tritrophic interactions among the Arizona walnut, Juglans major (Juglandaceae), the fly Rhagoletis juglandis (Diptera: Tephritidae), whose larvae feed on the husk surrounding walnut fruits, and the parasitic wasp Biosteres juglandis (Hymenoptera: Braconidae: Opiinae) which oviposits in the fly larvae. The foraging behavior of female Biosteres juglandis was studied in the field and greenhouse, with specific attention paid to their use of visual and olfactory cues produced by walnut fruits harboring R. juglandis larvae. Field work demonstrated that wasps are successful in locating fruits infested with host larvae interspersed among uninfested fruits, and that they use fruit phenological traits (i.e. stage of rot) to do so. The method by which females appear to choose fruits in the field is functional, provided there are high host infestation levels. In greenhouse assays, fruit damage (apart from larval presence) was specifically identified as an important cue affecting wasp fruit choice. Wasps are also able to orient to infested fruits using only one type of cue, either olfactory or visual. Preliminary data from a pilot analysis of volatile compounds associated with infested, uninfested, and artificially damaged walnuts indicated that visual cues were more important than olfactory cues to free-foraging wasps. Rhagoletis juglandis adult females visit walnut fruits for oviposition, while adult males visit them to obtain matings. The effect of fruit color pattern on the behavior of male and female flies both inexperienced and experienced with real ripe walnuts was studied in the greenhouse. Overall, both sexes of flies exhibited a landing preference for plastic fruit models that appear ripe and uninfested, over models that appear infested. The behavior of both sexes may be driven by females who are attempting to provide offspring with the most possible food resources. Finally, the growth and germination of Arizona walnut seeds was followed to determine whether either was affected by infestation of the husk by R. juglandis. Although infested fruits were more likely to fall off a tree sooner, this did not affect the size of a walnut or its ability to germinate.

The diversity of many groups of organisms is related to the evolution of features that contribute to rapid radiations. This project reconstructed the phylogeny of carabid beetles in the subfamily Harpalinae, a speciose group of terrestrial predators. The phylogenetic inference focused on the sister group relationships, the monophyly of the subfamily and the tribal relationships within harpalines. Molecular sequence data, primarily from 28S ribosomal DNA and the wingless gene, were collected from more than 200 carabid beetles. Parsimony, minimum evolution distance, maximum likelihood, and Bayesian phylogenetic analysis methods were used to reconstruct the phylogeny of harpalines. Brachinine bombardier beetles and austral psydrines were found to be closely related to the harpaline clade. Within harpalines, zuphiites formed a clear clade as did pseudomorphines + graphipterines + orthogoniines. However the lebiomorph assemblage and the tribe Lebiini were not monophyletic. With the use of harpaline phylogenetic hypotheses, the evolution of the arboreal lifestyle was elucidated within the subfamily, including the rate and number of origins and losses of arboreality. Correlated evolution of several morphological characters and habitat was explored. Significant correlation of adhesive subtarsal setae and bilobed fourth tarsomeres on carabid legs were found with arboreality and may be arboreal adaptations, while long legs and long elytra are probably not associated with arboreality. The relationship of other morphological characters with arboreality is not clear. Harpalines may have been part of a rapid radiation of species diversity, where many lineages invaded new ecological niches and evolved novel morphological features to become adapted to their environment.

In this dissertation I employ a comparative gene expression approach to address the evolution of butterfly wing pattern formation at several levels, with emphasis on early pattern determination and pigment gene regulation during late development. Expression analysis of the receptor molecule Notch suggested previously unknown roles for Notch signaling in butterfly wing patterning. Notch upregulation was found to precede the activation of the transcription factor Distal-less during early eyespot color pattern determination. A phylogenetic comparison of expression time series from multiple moth and butterfly species suggested that changes in a Notch/Distal-less temporal pattern formation process were associated with the gain and loss of both eyespot and midline color patterns during wing pattern evolution. Additionally, Notch expression was found to occur in a grid-like pattern in the butterfly wing epithelium shortly after pupation. This observation, together with previous expression and simulation studies, support a Notch-mediated lateral inhibition model of wing scale organization. Tryptophan-derived ommochrome pigments are a derived feature of nymphalid butterfly wings. I found that multiple genes in the ommochrome biosynthetic pathway were expressed in the wings of selected nymphalid butterflies. Additionally, transcriptional regulation of genes encoding the ommochrome synthesis enzymes vermilion and cinnabar was found to be temporally and spatially associated with the polymorphism and development of forewing band patterns in the mimetic butterfly Heliconius erato. These findings provide evidence that changes in ommochrome gene regulation underlie the evolution and development of major nymphalid wing pattern elements.

I examined resistance to cold temperature in seven Drosophila species from different habitats to determine the lower limits of cold tolerance. Three separate tests were administered to measure the: (1) response to a cold-shock exposure; (2) extent to which a short-term survival strategy, rapid cold hardening, was utilized by each species; and (3) degree to which each species would respond to a prolonged exposure at 0°C. As expected, the temperate-montane species, D. pseudoobscura, was the most cold-tolerant, whereas the least cold-tolerant was the tropical species, D. paulistorum. The two cosmopolitan species, D. hydei and D. melanogaster, and the three Sonoran Desert endemic species, D. mojavensis, D. nigrospiracula, and D. mettleri, demonstrated intermediate levels of cold-tolerance. Of the five species tested for rapid cold hardening, all exhibited the response, including the tropical representative. The results for the 0°C test paralleled the results of the cold shock test. The desert species tested proved surprisingly cold-tolerant, especially D. mojavensis.

Two factors affecting the mutualism between Myrmecocystus mendax and Publilia modesta are investigated. These factors are the seasonal time frame during which the mutualism is maintained and the behavior of individual workers tending membracid aggregations. Results of this study show that Publilia modesta makes seasonal migrations via flight, makes use of a conifer as a long term host, mates on a substate distant from a suitable oviposition host, and changes color with the onset of ovarian development many months after metamorphosis. Membracid-tending Myrmecocystus mendax comprise a behaviorally distinct subcaste and behave in a manner consistent with optimal foraging theory by maintaining both site and resource fidelity.

Blood fed Culex quinquefasciatus were collected from residential and wetland sites in Tucson, Arizona for three years using CDC gravid traps. An ELISA distinguishing human, bird, dog, cat, and rabbit blood meals was used. In residential areas, approximately 47% of all identified blood meals were from humans, with fewer blood meals from bird, dog, cat, and rabbit. At Sweetwater Wetland, humans were also the most common host, with 11 (41%) identified blood meals. Birds were the hosts of 19% blood meals. Ten (seven residential, three wetland) mosquitoes were identified to have blood from both bird and human hosts. Since the transmission of West Nile Virus to humans is dependent on mosquitoes feeding both on birds and humans, this finding is particularly relevant. These data only describe the feeding choices of the mosquitoes collected from a limited number of sites in Tucson, and therefore, may not reflect feeding preferences more generally.