<p> Hybrid poplars are a short rotation woody crop grown for a variety of target markets including paper pulp, saw timber, and biofuels in the Pacific Northwest. Development of pest control strategies within hybrid poplar plantations over the last several decades has focused on controlling foliar feeding herbivores and wood boring pests, and has overlooked the epigeal arthropod community. Understanding this unstudied suite of organisms would allow pest managers to better evaluate the impact their management strategies have on the poplar agroecosystem. Qualitative surveys of the arthropod communities in hybrid poplar plantations and nearby native habitats demonstrated that a greater arthropod diversity persists in the surrounding native areas. Additionally, the poplar plantation's epigeal arthropod community was composed of species found within sampled native areas. </p><p> Historically poplar research focused on protecting trees in the years following establishment through harvest from emerging pests while discounting cutting mortality by replanting areas of failure. Describing unrooted cutting transplant morality and distribution within newly established planting block could provide a risk assessment tool that growers could utilize to evaluate their potential crop loss. It was determined through the examination of damaged cuttings that several pests were responsible for diminishing establishment success. Identification of these risks led to the development of a management strategy to reduce mortality in newly planted areas. Soaking cuttings in imidacloprid for 48 hrs provided superior herbivore protection for unrooted cuttings until root formation allowed for uptake from chemigation treatments. </p><p> An additional study was motivated by the increased concern in growing `clear wood' as poplar has migrated from pulp to saw timber. The accompanying renewed interest in reducing insect galleries in mature trees led to the exploration of deploying a mass trapping, or trap out, effort to reduce populations of <i> Prionoxystus robiniae</i> (Lepidoptera Cossidae) in specific areas of a hybrid poplar plantation. We show that a trap out effort of roughly 5 pheromone-baited traps/ha decimated <i>P. robiniae</i> populations in treated areas throughout the trap out effort and three years post application.</p>

<p> I found that in inbred females <i>D. melanogaster,</i> physical condition plays a major role in the amount of polyandry. In some systems there is evidence that the ability to self assess allows inbred females to vary their reproductive behavior to increase promiscuity. I predicted that this may be true in <i>Drosophila melanogaster</i> females, but we found that inbred females behaved less promiscuously in three proxies than outbred females. Inbred females mated with fewer total males, fewer different males, and had longer copulation latency than their outbred conspecifics. However, male mate choice is not predicted in <i>Drosophila melanogaster </i> because males invest less than females, but recently the importance of male preference has been gaining support. How these males are making decisions is an important component to understanding the evolutionary impacts of the male's behaviors. I found that male mate choices are heavily influenced by previous experiences, and the lack of experience causes significant changes in courtship latency and overall preferences.</p>

<p> Male katydids produce mating calls through stridulation to attract potential mates. Calls were recorded in the field and analyzed to compare between two related species that occur in overlapping ranges in the northwestern United States. Distinct differences were found between the two species' calls in both dominant frequency and chirp rate. Also, one species interspersed trills amongst the chirps of the call, while the other species' call did not include trills. These distinct call differences can be used for species identification and can be easier to differentiate than physical characteristics. </p><p> The upper limits of sexual selection can be estimated using upper limits on Bateman gradients, which represent how fecundity increases with additional mates. Upper limits on Bateman gradients are expected to be constrained by various factors such as nutrition. These upper limits were estimated using controlled mating experiments with katydids on high and low protein diets (as adults) by measuring how maximum fecundity (fecundity with ideal mates) increased with each mating. Decreases in both maximum fecundity and the potential for sexual selection were expected in males and females due to protein limitation. This would result from decreased potential fecundity in low protein females and decreased value of nuptial gifts given by low protein males. The results did not support our predictions as strongly as hoped, but a decrease in the upper limits of sexual selection was nearly significant in low protein males, evidenced by reduced fecundity gains from remating. Also, spermatophores (the katydid nuptial gift) had a more complicated effect on fecundity than expected. Spermatophore size differed between males' first and second matings, however, larger spermatophores did not always confer more value to females, particularly in second matings. </p><p> Stable isotope analysis was used to examine the lack of significant effects from differences in dietary protein on the upper limits of sexual selection in the previous experiment. Stable isotope ratios were analyzed for three body tissues to infer diet at different life stages by comparison with isotopic values from the foods. Results showed that animals on the low protein diet may have eaten more food to make up for their protein deficit, which would have confounded nutritional effects in the previous study. Sex differences in nutrient processing were present as would be expected if males and females experience different nutritional requirements for reproduction. Nutrient processing in exoskeleton varied across food treatments in males but not in females. This suggests that males experienced greater protein limitation than females and adjusted their nutrient processing accordingly. Further work is underway to determine how much of each type of food was consumed by individuals in different experimental treatments and during different life stages. </p>

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Lady Bird Lake and Lake Austin are adjacent reservoirs in Austin, Texas, with the primary functions of electrical power generation, flood control, and recreation. In 1999, the invasive submerged aquatic macrophyte (SAV), Hydrilla verticillata, was observed in Lake Austin where it established over the span of the lake, though never establishing in Lady Bird Lake. Management strategies to eradicate hydrilla included the stocking of sterile Asian grass carp, Ctenopharyngodon idella. This practice nearly eliminated hydrilla and resulted in the decline of native aquatic vegetation and increased shoreline erosion. Conservation efforts to reestablish the vegetation are underway. SAV, in addition to facilitating nutrient uptake and retention, enhancing water clarity, stabilizing substrate, and attenuating wave energy, provides food and refugia for aquatic fauna. My research aims to understand the biological implications of the restoration of various SAV assemblages by analyzing the macroinvertebrate communities present within bare, mixed, and monocultured habitat regimes. The data suggests that mixed-cultured SAVs, site disturbance, substrate composition, and macroinvertebrate taxonomic resolution are the primary determinants of macroinvertebrate richness, abundance, and diversity.

Leaf litter is a major nutrient source for aquatic detrital food webs, fueling the microbes and macroinvertebrates that colonize it. Litter is especially important as a nutrient source for macroinvertebrates in headwater streams that tend to have lower primary production than higher-order stream systems. Understanding how litter decomposition and macroinvertebrates interact at large scales facilitates predictions about how stream ecosystems will change over space and time with regards to allochthonous nutrient inputs. We utilized a subset of the National Ecological Observatory Network's wadeable stream sites to deploy a litter pack study across the United States and Puerto Rico to determine the controlling factors for litter decomposition and associated macroinvertebrate assemblages, abundances, and species richness at a national scale. We found that litter species was the most important contributing factor to litter decomposition, and despite litter decomposition differences from stream to stream, the relative differences in decomposition rate between litter types was very similar. Stream identity, temperature, and flow also played roles in affecting decomposition patterns. In contrast to litter decomposition, litter species did not significantly contribute to variation in macroinvertebrate assemblages, abundance, or species richness, though environmental variables did impact abundance and species richness. These results suggest that there is functional redundancy in aquatic detritivore communities at large scales, and that the assemblages colonizing different species of leaf litter–despite being similar–might be functioning differently.

Doctor of Philosophy / Department of Entomology / James F. Campbell / Phillip E. Sloderbeck / Robert "Jeff" J. Whitworth / Knowledge of factors influencing the establishment, persistence and distribution of stored-product pests aids the development of effective Integrated Pest Management (IPM) programs in food storage and processing facilities. This research focused primarily on Tribolium castaneum, which is one of the most important pests of mills. Populations of T. castaneum from different food facilities can potentially be interconnected by either their own dispersal behavior or by human transportation. Population genetic structure analyses based on microsatellites and other insertion-deletion polymorphisms (“indels”) showed that populations from different mills around the US are genetically distinct from each other, but the level of differentiation was not correlated with the geographic distance. A potential source of insect infestation within a food facility is spillage that accumulates outside or movement from bulk storage facilities on site. Results from three facilities showed that most stored-product species were captured both inside and outside buildings, but T. castaneum was rarely captured outside of the facilities. Spatial distribution of all species outside was associated with the proximity of buildings, not necessarily with areas with accumulated spillage. T. castaneum populations inside facilities are potentially exposed to frequent genetic bottlenecks resulting from structural fumigations. Changes in allele frequencies through time, based on the analysis of microsatellites and other indels in individuals collected in a mill, confirmed bottleneck effects. To understand how spatial distribution of T. castaneum within a mill could be influenced by environmental and physical factors, a range of variables were measured at each trap location. There was significant variation among trap locations regarding beetle captures and the variables measured, but increase in beetle captures correlated only with increase in temperature and spillage production. Tribolium castaneum response to visual cues could influence attraction to pheromone and kairomone olfactory cues used in traps. Results of laboratory experiments showed that adults respond to tall narrow black shapes and placing traps in front of these shapes can increase captures. This research provides new insights into factors influencing the spatial distribution of T. castaneum and could help in improving monitoring programs for this important pest of the food industry.

Doctor of Philosophy / Department of Entomology / David C. Margolies / James R. Nechols / Foraging traits such as prey consumption rate and the efficiency with which predators convert their prey into offspring are important determinants of local predator-prey dynamics. However, in environments with patchy prey distribution, predator dispersal and aggregation in response to prey-induced volatile cues becomes more critical. My dissertation addressed predator-prey population dynamics in response to variation in four foraging traits in the predatory mite, Phytoseiulus persimilis (Acari: Phytoseiidae): consumption rate, conversion efficiency, dispersal, and olfactory response related to prey. The dispersal response and olfactory sensitivity in predatory mites is modified by prey-related cues. For example, the dispersal response increased with decreasing prey density in a patch and increasing prey-related volatiles from outside the prey patch. The olfactory response of predatory mites also increased with increasing numbers of prey per plant or with the length of time a plant was infested by prey. These results formed the basis for development of bioassays used to examine genetic variation in dispersal and olfactory response of predatory mites. Through artificial selection I documented additive genetic variation in all four traits. After relaxation of selection, high-level phenotypes were stable compared to their low counterparts. There were significant genetic correlations between some of the foraging traits. However, there were no correlations between foraging traits and life-history traits. The existence of genetic variation and covariation among the foraging traits suggests that predatory mites must be able to adopt different foraging strategies in the evolution of prey-finding in a tritrophic system. High consumption, high conversion efficiency and high dispersal response phenotypes interacted differently with prey in a spatially complex landscape. All foraging traits were comparable in terms of predator-prey densities and plant damage; but they were lower than the unselected control. Spatial association and correlation analysis showed that all foraging traits were positively associated with prey; but the strongest association was observed for the high conversion efficiency and dispersal lines. The variability in foraging behaviors of the predatory mite affects its ability to locate patchily distributed prey, thereby influencing foraging efficiency and population dynamics. This research provides new information about the critical link between predator foraging and population dynamics relevant to biological control.