The Tachinidae is a taxonomically and ecologically diverse clade of parasitoids for which evolutionary and ecological relationships with hosts are largely unknown. Here, I employed a multidisciplinary approach to evaluate the determinants of patterns of host use in the Tachinidae. First, I examined spatio-temporal variation in the tachinid-dominated parasitoid assemblage of one lepidopteran species Grammia geneura . The parasitoid assemblage and parasitism rates varied dramatically among and within sampling sites, seasons, and years. I show that this variability may be a function of habitat-specific parasitism and indirect interactions between this host and other Macrolepidoptera through shared tachinid parasitoids. I then experimentally examined the host selection process in the tachinid Exorista mella. Host movement was an important elicitor of attack behavior. Flies also responded to odors associated with food plants of their host. Experienced flies attacked hosts more readily than did inexperienced flies. Based on these results, I proposed a host selection scenario for this tachinid species. E. mella also teamed to associate colors with hosts and avoided deterrent models that they had experienced. However, I failed to find evidence for odor learning. Learning of host-associated cues by E. mella may allow this parasitoid to take advantage of abundant host populations and maintain host-searching efficiency in an unpredictable environment. To examine how host-associated characteristics evolved in the Tachinidae, I reconstructed the evolutionary relationships within the subfamily Exoristinae using molecular data. Phylogenetic analyses generally supported recent classifications. Analyses of host-related characters indicated that tachinids show great evolutionary lability in behavior, morphology, and host range. Finally, I sampled host species to assess the determinants of tachinid community structure and host range. Several host characteristics were found to affect tachinid species richness. These patterns may be due to the opportunistic use of abundant hosts by polyphagous tachinids, enemy-free space provided by well-defended hosts, and the process of host location. Patterns of tachinid host use varied significantly with sample size, host diet breadth, host gregariousness, plant form, and host morphology. Taken together, these studies indicate high levels of plasticity in tachinid-host associations. This may be responsible for their ecological and evolutionary success.

How will the intrusion of other species that remove rewards without providing reciprocal services affect the interaction between mutualists? How do costs and benefits from these "cheaters" compare to costs and benefits from potentially mutualistic visitors? Finally, did nectar-robbing, one kind of cheating, promote the evolution of complex levels of sociality by allowing bees access to a wider range of resources? I investigated these questions in the research described below. I found that pollinators visiting Chilopsis linearis (Bignoniaceae) spent less time visiting robbed flowers than visiting unrobbed flowers, and did not visit them as often as expected. Thus, robbing appeared to have a negative effect on pollinators visiting Chilopsis linearis . I compared costs and benefits of floral visitors to Chilopsis linearis (desert willow). Chilopsis had sensitive stigmas that closed immediately upon touch and may have reopened later. I found that the probability of stigma reopening depended on the source and number of pollen grains deposited. I compared visitors by number of pollen grains deposited, viability of pollen that they deposited, and their effect on stigmas. Nectar-robbers did not benefit plants by pollen deposition, but they also did not cost plants by causing stigmas to close without adequate pollen having been deposited. I investigated the effects of robbing on pollinator behavior and plant reproductive success. Nectar volumes were lower in robbed flowers than in unrobbed flowers. However, the most effective pollinators, bumblebees, did not avoid robbed flowers. In investigating male reproductive success, I found that on some days, dye mimicking pollen traveled farther from robbed flowers, indicating that robbing may sometimes be beneficial to plants. In investigating female reproductive success, I found that there was no difference in pollen tube number between robbed and unrobbed flowers. Thus, a negative effect on one mutualist may not affect the other mutualist. I hypothesized that the evolution of robbing in bees was associated with a broad diet breadth and the evolution of complex sociality. Using phylogenetically independent contrasts for taxa within three geographical regions, I found that in some cases, a broad diet breadth was associated with sociality and robbing.

Frankliniella occidentalis response to color hue and intensity was tested in both field bioassays and electrophysiology of the thrips eye. Results of electroretinograms demonstrated that males and females have a double peak spectral efficiency in the ultraviolet near 365nm and in the green-yellow range at 540nm. Results of field tests suggest, based on density change relative to sex ratio change between behaviors, that there was a greater change in male behavior (i.e. density) than in female behavior. Higher densities of thrips were observed on blue, violet, white and yellow hues. Interactions between the UV and green photopigments and integration of visual stimuli within the central nervous system may allow for discrimination of blue and violet colors, that are at wavelengths between the two peaks. Because the peaks of spectral sensitivity and the relative efficiency are the same between sexes, and the relative rankings of density remains the same between behavior periods, the greater change in male versus female behavior may be the result of complex behavioral responses to many possible cues as yet undetermined.

<p> In the first chapter, we revise the taxonomy of a lineage of plant bugs (Hemiptera: Miridae) that has radiated in the islands of French Polynesia. Six species of endemic <i>Pseudoloxops</i> plant bugs were previously known from two islands in French Polynesia, indicating a small radiation. We collected ecological, morphological, molecular, and geographical data for hundreds of fresh and historical <i>Pseudoloxops</i> specimens, expanding the genus' range to nine islands in two archipelagoes (the Austral and Society Islands). We combined all of the above data sources in an iterative integrative taxonomy framework to test the six existing species hypotheses and to search for new diversity. </p><p> In the second chapter, we explore the relative importance of ecology and geographic isolation in this lineage to provide a first approximation of whether the radiation was adaptive or non-adaptive. We collected <i> Pseudoloxops</i> from a wide range of plants, with 27 species in 25 different plant families and 13 orders. We then inferred a combined Bayesian molecular phylogeny from three genes, including 25 of the 26 known <i>Pseudoloxops </i> species, to examine the roles of plant affiliation and geography (island distribution) in speciation. We reconstructed the ancestral states using parsimony for these two characters, and found 12 speciation events that were well-supported in the phylogeny. Both plant-switching and island-hopping were correlated with speciation. For the 7 speciation events for which we could unequivocally determine plant affiliation before and after speciation, 4 were associated with a plant shift. For the 8 speciation events where island distribution could be reconstructed, two involved shifts to a new island. There were 5 cases for which we could determine both character states before and after speciation. In three of them, speciation occurred within the same locality with a switch in plant taxonomic order, suggesting that the lineage has great dietary versatility. However, much more research into feeding needs to be conducted, as anecdotal evidence from <i>Pseudoloxops</i> outside of French Polynesia suggests they may be facultative predators. In the other two speciation events, there was neither a geographic shift nor a change in plant affiliation, suggesting some other mechanism for speciation. Based on our results, both plant-switching and geography have played a role in the diversification of this radiation. </p><p> In the third chapter, we address the larger societal impact of taxonomic and biodiversity research by examining the effect of a natural history-driven curriculum on elementary schoolchildren's scientific knowledge. While studies have demonstrated the potential for natural history education to improve children's attitudes towards and knowledge of science and nature, few studies have been done in areas where indigenous culture heavily influences children's worldview. The lead author taught a nine-month natural history/biodiversity class focused on insects and plants to fifth-graders at the Pao Pao elementary school on the French Polynesian island of Moorea and tested their scientific knowledge before and after receiving the program. We compared their results to a control that did not receive the program, and while both cohorts improved, the experimental group's improvement was significantly greater (mean of 82.2% vs. 30.5%). We performed a delayed post-test evaluation three years after the conclusion of the program with a subset of the experimental cohort to test their retention and interest in science. Finally, the qualitative coding of the experimental group's test and survey responses revealed both the influence of indigenous culture on their scientific understanding and the appeal of taxonomy and field trips to children. When prompted for an example of a native plant, 24% of the experimental group named a plant introduced by the Polynesians, suggesting the misconception that plants with a prevalent role in indigenous culture have always been there. In the follow-up survey, 36.7% mentioned the field trips among their memories of the course, and 20% gave full scientific names for species they recalled from the class. The latter contrasts with the commonly held belief that taxonomy is too arcane to connect with the general public. (Abstract shortened by UMI.)</p>

During a screen for novel genes involved in the process of neurotransmission, a gene, bemused, was identified as the result of a transposon insertion at 85D on the third chromosome. Mutation of bem produces flies that are extremely uncoordinated and unable to fly. Subsequent electrophysiological recordings performed at the neuromuscular junction revealed neuronal hyperexcitability of bem mutants. Mutation of bemused also results in female sterility and reduced male fertility, both of which were determined to be the result of defects in oogenesis and spermatogenesis, respectively. Oogenesis defects include actin membrane degeneration within the egg chamber, resulting in nurse cell fusions and mispositioned nurse cell nuclei, abnormal dorsal appendage formation and in severe cases, a misplaced or absent oocyte. These phenotypes are often observed in mutants disrupting the cytoskeleton, suggesting bem may have a cytoskeletal function. Analysis of spermatogenesis revealed the lack of production and storage of mature sperm in the seminal vesicles of bem testes. Homozygous bem females deposit a small number of superficially normal eggs that fail to hatch, thus defects in embryogenesis were hypothesized. Indeed, the embryos of bem mothers have a number of defects in early embryogenesis, including the formation of polyploid nuclei presumably as a consequence of aberrant mitotic spindles, incomplete axial migration of the nuclei to the anterior pole, disruption of proper formation of the pole cells and abnormal syncytial blastoderm characteristics, such as nuclear withdrawal from the periphery and nuclear aggregates. These abnormalities resemble defects observed in embryos treated with cytoskeleton-disrupting drugs, further supporting a role for bemused in the structure or regulation of the cytoskeleton. Approximately 15 kb of genomic DNA from the bem region was isolated but identified only questionable partial transcription units when used to screen cDNA libraries. Subsequent sequencing of the 15 kb of genomic DNA surrounding the bem P element insertion failed to identify any transcribed regions; therefore, long term cloning strategies have been initiated to identify the bem transcription unit, including the isolation of additional genomic DNA and the creation of additional bem alleles.

The work described involves the isolation and characterization of the gene encoding the calmodulin protein in the dipteran species, Drosophila melanogaster. The two major protein coding exons, designated 2 and 3, had been previously isolated. Together they encode 139 of a total of 148 amino acids. These exons were used to screen a D. melanogaster embryonic cDNA library in order to isolate clones containing sequences derived from the remaining exons. The clones obtained in this manner eventually led to the identification of two additional exons. Exon 4 contains the remaining protein coding sequences as well as the 3$\sp\prime$ untranslated trailer. Two different cDNA size classes were discovered, which, after sequencing, were found to result from the use of alternative polyadenylation signals. Northern blot analysis of polyadenylated transcripts isolated from 0 to 12 hour-old embryos confirmed the existence of two mRNAs of the approximate sizes 1.7 and 1.9 kilobases. Northern blot analysis of poly-A+ RNA isolated from developmentally staged animals revealed that the relative levels of these two transcripts vary in a stage-specific manner. Exon 1 was originally presumed to be the exon situated furthest 5$\sp\prime$, containing the translation initiation codon as well as all of the 5$\sp\prime$ untranslated leader. Primer extension and S1 nuclease analysis to determine the 5$\sp\prime$ limit of the transcription unit revealed the presence of an additional small 5$\sp\prime$ exon. Several cDNA libraries, both stage- and tissue-specific, were screened using sequences derived from exon 1 in order to isolate a clone complete at its 5$\sp\prime$ end. The sequence of the 50 residue exon 0 was therefore determined and used to locate the exon in genomic DNA. The genomic region containing the 5$\sp\prime$ flank of the transcription start site, exon 0, and the first intron of the gene was sequenced. Sequence comparisons of the 5$\sp\prime$ flanking region with those of other calmodulin genes were performed.

I examined biting, grooming, and inspection behavior in a pre-emergent colony of Parachartergus colobopterus, a neotropical swarm-founding wasp, to determine whether kin discrimination occurs between adult colony members. If within-colony kin discrimination exists, this is a likely place to find it. Low relatedness among colony members at some points in the colony cycle reduces advantages of nestmate discrimination and increases possible advantages of within-colony kin discrimination. I found no evidence of kin discrimination in length or frequency of biting and grooming interactions. Furthermore, interactants in biting, inspection, and grooming interactions were no more or less related than by chance. Results suggest that members of the species P. colobopterus do not identify and preferentially aid closer kin within a colony.

Why do females across a wide range of taxa mate with more than one male? Here, I present the hypothesis that females engage in polyandry as a hedge against genetic incompatibility. I review evidence from the literature showing that the genomes of species are dynamic entities, constantly evolving as a consequence of genetic conflicts within and between the nucleus and the cytoplasm. Cellular endosymbionts, segregation distorter alleles, transposable elements and genomically-imprinted genes can all threaten female fitness by modifying maternal and paternal haplotypes in ways that render them incompatible within the developing embryo. I discuss the potential for polyandrous females to utilize postcopulatory mechanisms such as sperm competition, female choice of sperm, and reallocation of maternal resources from defective to viable embryos in order to minimize the risk and/or cost of fertilization by genetically-incompatible sperm. In a sperm precedence experiment carried out on the pseudoscorpion, Cordylochernes scorpioides, single-locus minisatellite DNA fingerprinting demonstrated strong last-male sperm precedence when females were mated to two males which broke down completely when females were mated to three males. This result indicates that the opportunity for postcopulatory sexual selection may be much greater in nature than is evident from standard, laboratory, two-male mating experiments. Polyandry in this pseudoscorpion is shown to be a deliberate strategy which increases reproductive success. In laboratory experiments, females restricted to mating with a single male experienced a higher rate of embryo failure and produced significantly fewer offspring than either females mated to more than one male in the laboratory or females naturally inseminated in the field. Previously proposed hypotheses such as forced copulation, insufficient sperm from a single mating, male nutrient donations, offspring genetic diversity and inherent male genetic quality cannot explain this higher reproductive success of polyandrous females. Observations of meiotic drive, highly-skewed sex ratios and paternal effects on sex ratio in this pseudoscorpion are consistent with the hypothesis that, by accumulating sperm from several males, C. scorpioides females reduce the number of embryos which fail as a consequence of genetic incompatibility between maternal and paternal genomes.

In social insect colonies workers realize their reproductive potential through rearing the queen's brood. In the primitively eusocial wasp Polistes exclamans (Hymenoptera: Vespidae) castes are not morphologically distinct. This species has an annual colony cycle that begins when mated, hibernated females start colonies in the spring. One foundress becomes the queen while the rest become workers. The worker population grows throughout the year until the appearance of gynes, females that do not work but become foundresses the following spring. Males are also produced by the end of the season, but they die in winter with the workers. While morphological caste differences are absent, caste can be identified using behavioral and physiological parameters. In contrast with other social insects, female caste remains undetermined until adulthood, and even then females switch between castes under the appropriate circumstances. This can be advantageous since high nest predation rates and unpredictable environmental variation, accompanied by frequent queen supersedure are typical. I studied three aspects of the P. exclamans caste system: (i) morphology and physiology in gynes and workers; (ii) seasonal resource allocation into brood and (iii) effects of brood loss on caste determination. Physiological indicators were derived from qualitative and quantitative studies of biochemical components, and from measurements of metabolic rates. I show that differences between castes are mostly quantitative, rather than qualitative. I suggest that lack of physical and qualitative differentiation is what allows caste transitions. Seasonal resource allocation on brood shows that while young, adult females produced throughout the season increase in weight and size, energy reserves lipids peak in May and June. I suggest that this peak in reserves is related to high predation experienced by colonies during that time and that it allows females to reconstruct their nests more efficiently. Finally, I examine effects of loss of brood in late summer and early fall colonies showing that females that do not have the opportunity to care for brood develop gyne-like characters, but that females that have develop worker-like characters. These results show that caste in P. exclamans is plastic, behaviorally and physiologically, allowing individuals to respond to varying environmental and social conditions.

We were interested in identifying genes in the dipteran flies Calliphora erythrocephala and Drosophila melanogaster with a role in oogenesis and early embryogenesis. A biochemical screen was used to complement the extensive genetic screens that have been performed to identify such genes in Drosophila. Radio-labelled cDNA probes were made using poly(A)$\sp+$ RNA preparations from staged Calliphora ovaries and embryos. These probes were used to isolate clones which were strongly expressed during oogenesis but not during embryogenesis. Four Calliphora genes which are absolutely "oogenesis-specific" in their expression pattern, as defined by our screening protocol, were identified. These are called A10B, B8I, C7F and GG7K. Three of these clones are expressed in the somatically derived follicle cells of the ovary and have been identified as being homologous to the Drosophila yolk protein 1 (A10B and B8I) and a vitelline membrane protein (GG7K). Interestingly, the yolk protein homologs are expressed in a specialized subset of follicle cells known as the border cells in Calliphora. The fourth gene, (C7F) is expressed in the nurse cells, the transcripts are translocated to the oocyte proper and maintained throughout the first four hours of embryogenesis. C7F is also expressed in late pupae and adult male flies. A number of Calliphora genes were identified which, although not oogenesis-specific, were more strongly expressed in the oocyte than the embryo. These were classified as "oogenesis-differentials". C7F and the Calliphora oogenesis-differential genes were used to screen Drosophila cDNA and genomic libraries for homologs. Some characterization of these Drosophila homologs is described here. ME31B, a maternally expressed Drosophila gene from the 31B region of the second chromosome was isolated by directly screening Drosophila libraries with Calliphora cDNA probes. ME31B is expressed throughout oogenesis and the transcript is maintained in the mature egg until four hours after fertilization. The ME31B transcript is evenly distributed throughout the oocyte and egg. A 1.5 kb cDNA for ME31B was completely sequenced. Comparison of the coding sequence with a protein data bank allowed us to show that ME31B is a member of a family of NTP-dependent helicases. The possible mutant phenotype of ME31B is discussed.