<p> As herbivorous insects choose where to lay their eggs, maximizing larval performance (optimal oviposition) may be at odds with adult foraging (optimal foraging). Aspen leaf miners (<i>Phyllocnistis populiella</i>; ALM) may choose between leaves with or without extrafloral nectaries (EFNs) as oviposition sites on quaking aspen (<i>Populus tremuloides</i> Michx.). Reduced ALM mining on leaves with EFNs may be linked to predators that defend leaves and feed at EFNs, and to increased concentrations of secondary leaf compounds. However, direct responses of adult ALM to EFN expression may also explain differences in ALM mining among leaves with and without EFNs. ALM might be less likely to oviposit on leaves with EFNs because these leaves provide poor conditions for larval development. With choice experiments and surveys of ALM oviposition, we examined oviposition site preference in relation to EFN expression. In choice experiments and field surveys adults preferred to oviposit on leaves without EFNs. Increased oviposition was also observed on shoots with high EFN frequencies, suggesting a combination of optimal foraging and optimal oviposition, and a role of EFNs at scales above the leaf level. Higher predation on leaves with EFNs likely exerts selective pressure for the observed ALM oviposition preference for non-EFN leaves.</p>

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2008. / Source: Dissertation Abstracts International, Volume: 69-05, Section: B, page: 2736. Adviser: Andrew Suarez. Includes bibliographical references (leaves 83-99) Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2008. / Source: Dissertation Abstracts International, Volume: 69-11, Section: B, page: 6534. Adviser: Wesley M. Jarrell. Includes supplementary digital materials. Includes bibliographical references (leaves 134-152) Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2009. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3281. Adviser: Lawrence M. Hanks. Includes bibliographical references. Available on microfilm from Pro Quest Information and Learning.

<p> The rice stink bug, <i>Oebalus pugnax</i>(F.), is an important late season pest of rice that is noted for causing grain yield and quality reductions in the United States. This study investigated rice injury using field cages in two rice cultivars ('Cocodrie' and 'Wells') at bloom, milk, and soft dough stages and <i>O. pugnax</i> ecology in the Delta Region of Mississippi. </p><p> Specific objectives were: 1) to determine the impact of adult <i> O. pugnax</i> infestation on rice yield and grain quality at bloom, milk, and soft dough stages of rice development; 2) to determine the impact of adult <i> O. pugnax</i> gender and infestation duration on rice yield and grain quality at the milk stage of panicle development; 3) to identify and examine the seasonal abundance and phenology of <i>O. pugnax</i>on non-cultivated host grasses; and 4) to evaluate feeding preference and development of <i> O. pugnax</i> on host grasses. </p><p> Rice injury increased as <i>O. pugnax</i> density increased. The bloom and milk stages were the most vulnerable to blank and discolored kernels, respectively. <i>O. pugnax</i> feeding injury was significant after 3 d of infestation duration during the milk stage of panicle development. Female <i>O. pugnax</i> caused a greater percentage of blank kernels compared to males. </p><p> A survey of <i>O. pugnax</i> hosts indicated that Italian ryegrass, <i> Lolium perenne</i> L. ssp. <i>multiflorum</i> and winter wheat, <i> Triticum aestivum</i> L., were important hosts during spring and early summer. Junglerice, <i>Echinochloa colona</i> (L.) Link; crabgrass spp., <i>Digitaria</i> spp. Haller; southwestern cupgrass, <i> Eriochloa acuminata</i> (J. Presl) Kunth; and praire cupgrass, <i> Eriochloa contracta</i> (Hitchc.), were important hosts for <i> O. pugnax</i> during early to mid-summer. Browntop millet, <i>Urochloa ramosa</i>, and broadleaf signalgrass, <i>Urochloa platyphylla</i>, supported adult <i>O. pugnax</i> prior to overwintering. In a choice test of wild host grasses, junglerice was the most preferred over 10 other host grasses. In the no-choice test, mean development time was shorter and survival was greater for <i>O. pugnax</i> nymphs reared on rice, <i> Oryza sativa</i> L., compared to dallisgrass, <i>Paspalum dilatatum </i> Poir and junglerice. These results provide biological and ecological information on which new <i>O. pugnax</i> integrated pest management practices can be developed.</p>

<p> Various models of density dependence predicted different evolutionary outcomes for <i>Helicoverpa zea, Diabrotica virgifera,</i> and <i> Ostrinia nubilalis</i> using simple and complex resistance evolution models, different dose assumptions and refuge proportions. Increasing available refuge increased durabilities of pyramided Plant-Incorporated-Protectants (PIPs), especially between 1&ndash;5%. For some models of density dependence and pests, additional refuge resulted in faster adaptation rates. Significant considerations should be given to a pest's intra-specific competition in simple and complex theoretical models when designing insect resistance management plans. </p><p> Life-history, refuge, and dose characteristics of a PIP had different effects on the adaptation rate of a generic pest of Bt, and unexpected outcomes occurred. Intrinsic growth rate 'R₀' was the strongest evolutionary force, and large R₀'s reduced time to resistance for a high dose PIP to similar levels as projected for a low dose PIP. This was caused by differential density dependent effects in refuge and Bt fields that elevated generational resistance increases beyond those from selection alone. Interactions between density dependence and R₀ were always present and further affected the life-time of the PIPs. Varying 'average dispersal distance' did not affect evolutionary outcomes; however, increasing the proportion of the population engaging in dispersal often increased the durability of high dose PIPs. When resistance genes spread from a hypothetical hotspot, local resistance phenomena developed in the immediate surroundings. Higher growth rates lead resistance to spread faster through the landscape than lower rates. Increasing available refuges slowed adaptation rates to single PIPs and low dose pyramids, although non-linear trends were possible. </p><p> Integrated Pest Management (IPM) practices at the onset of PIP commercialization slowed pest adaptation rates. For corn rootworm, interspersing non-selective periods with IPM+IRM delayed resistance evolution, yet crop rotation was the best strategy to delay resistance. For bollworm inclusion of isoline corn as an IPM tool did not increase the life-time of the PIP. A local resistance phenomenon for rootworm was maintained immediately surrounding the hotspot; random selection of mitigatory strategies in the landscape slowed adaptation rates while mitigation in the hotspot alone did not. Mitigation extended the life-time of the pyramid minimally for both corn rootworm and bollworm.</p>

<p> Every interaction between species occurs in a heterogeneous environment that presents countless contexts that shape the interaction over time and space. The consequences of these interactions can regulate populations, as they trickle down to influence the genes that an individual passes on to its offspring, and then, in turn, scale back up to influence the genetic and phenotypic composition of future populations. In this work, I sought to uncover how these principles play out in the interactions between an invertebrate vector of human disease and the disease agent it carries. Disease vectors are often considered in a context that is faithful to the word as it is used in physics, where the vector is viewed as public transportation that moves the pathogen between hosts, experiencing no consequences of parasite infection. However, vectors face the challenge of how to maximize individual fitness in a stochastic environment with limited resources just as all other species do, so why would they be exempt from the effects of being parasitized? As such, I investigated the triatomine bug species <i>Rhodnius prolixus</i> when infected with the parasite <i>Trypanosoma cruzi</i> (etiological agent of Chagas disease), and co-infected with <i>T. cruzi</i> and its sister species, <i>T. rangeli.</i> I asked, does <i>T. cruzi</i> affect <i>R. prolixus</i> fitness, and under what contexts does this effect vary? I found a large range of variation in <i> R. prolixus</i> fitness when infected with <i>T. cruzi,</i> with the outcome being influenced by parasite strain, co-infection with <i> T. rangeli,</i> parasite dose, and the timing and order of infection. These factors did not act alone, but seemed to be dependent on one another: it was better to have a co-infection at lower <i>T. rangeli</i> doses, but at high <i>T. rangeli</i> doses, it was better to be infected with <i>T. cruzi</i> first, suggesting an interaction between dose, order and timing. These results illustrate the interactions across scales of both biological and spatio-temporal complexity that can be revealed when studying infectious disease through an ecological lens. Moreover, this work emphasizes the importance of taking into account the ecology of vector-borne neglected tropical diseases such as Chagas disease.</p>

<p> Recent research has revealed a trend of decreasing pollinator abundance and diversity in regions throughout the world. This highlights the need to understand factors influencing patterns in bee community structure and the drivers of bee diversity and abundance patterns. My dissertation uses several methods to determine factors structuring bee communities with regards to diversity and abundance. I selected 10 sites in different regions of the Central Valley of California that differ with regards to land use and floral diversity. Bee communities at each site were sampled for diversity, abundance, and bee-floral host relationships. </p><p> Sampling bee communities is often done using only bee bowls because netting is time consuming and prone to sampler bias. In chapter one the methods used in this study were detailed and the use of bee bowls and netting in capturing a representative sample of the bee community were compared using the S&oslash;rensen's similarity index and the Bray-Curtis dissimilarity index. It was determined that sampling using one method alone would miss approximately 40% of the species richness of the community. Further, there were biases in using bee bowls and nets; the bee bowls sampled certain species more than nets and vice versa. This chapter provides evidence that to adequately sample a bee community both bee bowls and netting must be used. </p><p> Chapter two focuses on bee biodiversity and the correlation between bee species richness and plant diversity. Patterns of diversity in bee communities of the Central Valley indicate that the family Apidae was more speciose than other families. However, on a species level, those from the family Halictidae far exceeded species from Apidae in abundance. This could have reflected a sampling bias given that pan traps tend to sample individual bees from Halictidae more than Apidae. Chapter two also focused on temporal variability. There was considerable temporal variability in the abundance of one of the more abundant species, <i>Lasioglossum incompletum.</i> This highlighted the need for studies of longer duration in order to account for natural stochasticity in bee populations. Several different diversity indices were used to assess the biodiversity of the different study locations; Putah Creek sites were found to be more diverse than the San Joaquin sites. A correlation analysis was used to determine that a positive relationship between plant diversity and bee species richness did exist for 2005 but not 2006. This indicated that plant diversity may be one of the factors driving bee species richness and community structure. </p><p> Another factor possibly accounting for variation in bee species richness and abundance is land use. Chapter three used non-metric multidimensional scaling and generalized linear mixed effects model to test for associations between differences in land use patterns and bee species richness and abundance. While there was no direct association between these factors, the ordination did show that the Putah Creek sites, San Joaquin sites, and Cosumnes sites clustered together. Therefore, sites that shared similar land-use patterns were related along a gradient. These cluster patterns were used to group the study locations for the other analyses performed in this project. The Putah Creek sites were characterized by agriculture and urban land use whereas, San Joaquin was semi-natural and Cosumnes Preserve was semi-natural and agricultural. </p><p> Chapter four is an analysis of the pollinator networks of Putah Creek, San Joaquin, and the Cosumnes Preserve. Pollination webs, matrices, and gplots were used to visualize the networks, while network and species-level indices were used to assess asymmetry, specialization versus generalization, and connectance. It was determined through these analyses that the connectance of the network decreased with increasing species richness and the complexity and composition of the network varied between the three regions of the Central Valley. Further, the San Joaquin Refuge sites, which were characterized as seminatural land use, contained a higher number of oligolectic species than other sites dominated by agricultural and urban land use. </p><p> The focus of this project was to use different methods to determine drivers of bee species diversity and abundance in different bee communities of the Central Valley of California. Three conclusions can be drawn from the analyses presented; 1) Given temporal variability in bee populations, studies of longer duration must be conducted to determine factors affecting bee community structure from that of natural population variability, 2) Floral diversity is positively correlated with bee species diversity and abundance but it is not the only factor influencing bee community structure. and 3) Land use change may be a factor influencing bee-plant networks but studies that compare networks across space and time are needed to determine the nature of this relationship. </p>

<p> The goldspotted oak borer (GSOB), <i>Agrilus auroguttatus</i> Schaeffer, is an invasive wood-borer associated with tree mortality in San Diego County, California since 2008, and is believed to have been introduced via infested firewood from southeastern Arizona. From 2011-2013, I recorded GSOB emergence holes on <i>Quercus agrifolia</i> trees at eight locations within San Diego County. I evaluated the effectiveness of crown class and purple prism traps as tools to monitor GSOB populations. I also identified possible tree and site characteristics that could explain the variation in GSOB population densities. Crown class was useful in monitoring GSOB populations unlike purple prism traps. Larger trees (>50 cm diameter at breast height), trees located near a stand's edge, and trees previously infested had the greatest emergence hole densities. Sites closer to GSOB's putative original point of infestation and those with an intermediate <i>Q. agrifolia </i> density (30-50 trees per hectare) had greatest infestation levels. </p>

<p> The burying beetle <i>Nicrophorus orbicollis,</i> through biparental care, raise their young on small vertebrate carrion which exposes them to microbial parasites and competitors. These interactions have led to elaborate strategies to combat microorganisms. Through the application of anal and oral secretions adults are able to preserve a carcass from which larvae feed, constituting a social immune response. Evidence suggests that larvae also contribute to this social immunity through their own secretions. Social immunity was tested through exposing larvae to an isolated food source with an experimentally elevated microbial signal, dead <i>Micrococcus luteus.</i> Larvae maintained higher lysozyme-like activity (LLA) in their oral secretions in response to the microbial signal. However, if personal immunity was compromised LLA was not maintained. Larvae and parents were tested for response to increased competition of feeding on fresh or aged carcasses with greater levels of decay. Larvae were not shown to alter LLA of their oral secretions but female parents did have a negative relationship of LLA in their oral secretions and in relation to brood size. Larvae had a negative relationship of phenoloxidase activity in their oral secretions in relation to brood size. This suggests influence of individual larval investment to social immunity affecting both parents and sibling investment. These findings show that oral secretions in <i> N. orbicollis</i> larvae, like adults, has adaptive antimicrobial activity which acts as a social immune response for defending a carrion food source and is sacrificed for personal immunity.</p>