Insects exhibit considerable variety in their morphology and can be found in many diverse habitats. Despite these variations, early neurogenesis seems to be conserved in insects. In all species investigated to date it begins with the formation of neural stem cells (neuroblasts), which establish a distinct internal layer and produce a fixed number of neurons and glial cells. The neuronal cells then form a characteristic rope ladder-like axonal scaffold. However, it is evident that the composition or identity of the individual neurons must have changed during insect evolution to allow for variations in neuronal networks. This raises questions regarding which developmental steps have been changed and the manner in which they have been modified. In order to address these questions, early neurogenesis was analysed in the flour beetle Tribolium castaneum and the results were compared to the well-studied fruit fly Drosophila melanogaster. Initially a map of trunk neuroblasts in T. castaneum was established, which revealed a high degree of conservation in the arrangement of individual neuroblasts compared to D. melanogaster. However, a comparison of the expression patterns of genes that confer regional identity to neuroblasts showed considerable variations. Significant differences in the expression patterns of the segment polarity gene wingless and the columnar gene ventral nerve cord defective (vnd) were found. Furthermore, the impact these changes in neuroblast identity have on the composition and identity of their respective progeny was analysed. As a result changes in the number of Even-skipped and Tailup expressing neurons in T. castaneum embryos were found, with three-fold more Tailup expressing neurons compared to D. melanogaster. To further analyse the role of the neuroblast identity gene vnd in the formation of Even-skipped positive neurons, RNAi gene silencing studies were performed, resulting in the loss of neurons and changes in neuronal migration pattern. In summary, the results demonstrate that evolutionary changes in neuronal networks result from changes in neuroblast identity, which in turn have an impact on the composition of neuronal lineages.

<p> The grape industry in Oklahoma was valued at $98 million in 2010. In 2015, symptoms resembling Grapevine Leafroll disease were observed, but Grapevine Leafroll-associated Viruses were not detected using enzyme-linked immunosorbent assay (ELISA). A 2-year Cooperative Agricultural Pest Survey was initiated to determine the etiology of the red leaf symptoms in Oklahoma vineyards. In 2016, a total of 121 symptomatic grapevines from 13 counties were sampled and 96 symptomatic grapevines from 14 counties were sampled in 2017. Each sample was tested for Grapevine Red Blotch Virus (GRBV), <i>Xylella fastidiosa </i> (Pierce&rsquo;s Disease), and &lsquo;<i>Candidatus</i> Phytoplasma spp,&rsquo; by polymerase chain reaction (PCR). ELISA was used to test for Grapevine Leafroll associated Virus (GLRaV) strains 1,3 and 4 strains. Rotbrenner, caused by <i>Pseudopezicula traceiphila</i>, (2017 only), can be found in xylem from petioles and the xylem was examined morphologically for signs of fungal structures. In 2016, GRBV was detected in 38% of 121 symptomatic samples, GLRaV-1 and -3 were detected in 16%, GLRaV 4 strains were detected in 2%, and <i>X. fastidiosa</i> was detected in 2%. There were no detections of &lsquo;Ca Phytoplasma spp&rsquo; in 2016 or 2017. In 2017, GRBV was detected in 34% of the 96 samples, GLRaV-1 and -3 were detected in 17%, GLRaV 4 strains were detected in 3%, and <i> X. fastidiosa</i> was detected in 3%. Rotbrenner was not detected in any of the samples in 2017. The findings of this survey provide information to Oklahoma grape growers and extension personnel about the cause of red leaf diseases affecting grapevines so that appropriate management strategies can be implemented in the near future.</p><p>

<p> The utilization of cover crops and no-till practices are important for the conservation of both soil and moisture in South Dakota. However, it is unknown if these practices impact the efficacy of insecticide seed treatments. In soybean, insecticide seed treatments are used prophylactically to prevent potential crop losses from early season insect pests. The prophylactic use of any management strategy increases the likelihood for selection pressure and also represents unnecessary input costs. The purpose of the research conducted for Chapter 2 was to determine the impact that tillage systems, cover crops and planting populations have on the efficacy of insecticide seed treatments. Two years of field data was collected from established long-term tillage and cover crop rotation plots at the South Dakota State University Southeast Research Farm. During each year, four factors were evaluated for their impact on yield (i.e., tillage, cover crop, seeding rate and seed treatment). Stand counts, soil samples and yield data were taken from each plot. In Chapter 3, we evaluated pyrethroid resistance in soybean aphid, <i>Aphis glycines</i> Matsumura (Hemiptera: Aphididae) populations in South Dakota. In 2015, the University of Minnesota discovered populations of the soybean aphid that were partially resistant to pyrethroid insecticides. Due to the soybean aphid&rsquo;s capacity for rapid reproduction and its ability to travel long distances in its alate (i.e., winged) form, it was determined that South Dakota may have resistant populations present. In 2017 and 2018, an efficacy study was deployed at three locations, over two years throughout Eastern South Dakota. A total of eight foliar insecticides were used in 2017 and 10 foliar insecticides in 2018. The results from chapter 2 indicate that seed treatment and cover crops have no significant impact on soybean yield. The results from chapter 3 determined that pyrethroid resistant soybean aphids are present in South Dakota.</p><p>

In the present study, I demonstrated the ability of the xylem-feeding leafhopper, Carneocephala floridana, to discriminate between differentially fertilized Spartina alterniflora, which possessed varying levels of foliar nitrogen content. The hopper was capable of detecting, and preferentially fed upon, minimally fertilized plants, which did not differ in percent of foliar nitrogen from unfertilized control plants. / Chemical analyses of the xylem sap and performance data from another host plant, Borrichia frutescens, confirmed that amino acid levels in highly fertilized plants become very unbalanced and are either unusable, or toxic, to C. floridana. Highly fertilized plants had elevated levels of NH$\sb4\sp+$, and a nitrogen content, that is probably well above those found in naturally occurring B. frutescens. These results suggested that a threshold detection mechanism may be operating. C. floridana's host plants show seasonal trends in their nitrogen content. While, the field patterns of C. floridana did not suggest that the hopper switches host plants based solely on interspecific nitrogen content; intraspecific nitrogen content did show several trends that were consistent host plant usage. My results suggest that the spatial and temporal distribution natural populations of C. floridana may be influenced by host plant nitrogen, but crude nitrogen is not a good predictor of interspecific host plant preference. / In addition, egg mortality and parasitism rates were also higher on the grasses compared to the herbaceous species. It appears that host plant water content may be largely responsible for plant mediated egg mortality. In addition, high parasitism rates on the two grass species may be related to the orientation of eggs, which are laid in parallel packets just below the surface of the epidermis. Conversely, eggs laid on the two herbaceous species appear to be less accessible to searching parasitoids. / My data suggest that Carneocephala floridana should utilize the two grasses only when the two herbaceous species are unavailable. In the salt marshes of Florida's northern Gulf coast, this occurs during the winter when the herbaceous species experience a substantial dieback. / Source: Dissertation Abstracts International, Volume: 52-08, Section: B, page: 4007. / Major Professor: Donald R. Strong. / Thesis (Ph.D.)--The Florida State University, 1991.

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No description available.

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A basic tenet of social structure is the assumption that the benefits of cooperative behavior must outweigh its costs if sociality is to evolve. The temperate spider, Anelosimus studiosus, exhibits a social behavioral polymorphism: individuals may defend asocial nests against intrusion by conspecifics or cooperate with them in multi-female nests. I initiated my investigation into this system by examining the extent to which social behavior phenotype is correlated with other behavioral traits and whether these correlations had adaptive consequences (Chapter 1). Using field surveys and laboratory experiments, I compared the success of asocial and social individuals in encounters over contested prey and prospective mates (Chapters 2, 3, 4). I then considered whether these trait correlations possess explanatory power for population-level divergence in behavior (Chapter 5). My results indicate social tendency is phenotypically correlated with several other types of behavior (e.g., activity-level, aggressiveness towards prey, exploratory behavior). The observed linkage between social tendency and other behavioral traits imposes a number of non-intuitive costs and benefits to possessing the social phenotype (e.g., social females are disadvantaged in agonistic interactions, but are more attractive to prospective mates). Finally, I examined the phenotypic correlations among behavioral traits for 18 different populations of An. Studiosus. I find that within- and between-population trait correlations resemble one another. Thus social tendency may not be “free” to evolve independently from other behavioral traits.

Large, heavily scaled tomocerid springtails (Collembola) are abundant in eastern forests, and are important components of the detrital food web. The genus Pogonognathellus predominates in the southern Appalachians While a number of well-delimited tomocerid species have been described, others have vague morphological boundaries and appear to be species complexes. Before this study began in 2005, four species were known to occur in Great Smoky Mountains National Park (GSMNP) and the surrounding Appalachians (P. bidentatus, dubius, elongatus, flavescens). Also occurring throughout the area is Tomocerus lamellifera, a widespread and distinctive species. The goals of this project were to correlate scale patterns and colors, ground color, morphology, and DNA sequences for separation of species; to describe any new species detected; and to redescribe known species. Scale patterns and molecular sequences have not been previously studied in North American Tomoceridae. We collected 432 specimens from diverse localities and maintained them in culture containers. After a specimen molted, it was photographed to capture the pristine scale pattern and color, then preserved in 100% ethanol (EtOH). The preserved specimen then was re-photographed for ground color (most scales are dislodged in preservative). Selected specimens were dissected and the various appendages (legs, mouthparts, furcula) were slide-mounted for morphological analysis. The torso was used to obtain DNA, from which the 5’-3’ exoribonuclease II gene was amplified, sequenced, and analyzed phylogenetically. Freshly collected specimens of P. flavescens from the type locality (Sweden), preserved in 100% EtOH, were provided by Arne Fjellberg and included in the analysis. Tomocerus minor and Harlomillsia oculata (Oncopoduridae) were used as outgroups for the phylogenetic analysis. A phylogenetic tree based on the molecular sequences was used to indicate relationships that then were tested with morphological characters, chaetotaxy, scale pattern, and color. Putative P. flavescens from North America were not grouped with Swedish specimens, raising the possibility that P. flavescens does not occur in North America. Pogonognathellus nigritus, previously synonymized with P. elongatus, was determined to be a valid species, and P. elongatus itself was found to be mis-described in most accounts. Two new species were identified: one from a cave in GSMNP which is closely related to a California cave species, and a second from several forest localities (i.e. GSMNP and Mount Mitchell, NC). A group of specimens ascribed to the flavescens/dubius complex also appear to represent several undescribed species, but more specimens are needed for further analysis.

We often study the outcomes of species interactions, whether they be predation, competition, or mutualism, at one site in a single year. However, we increasingly recognize that species interaction outcomes are not static, but context dependent by varying along many ecological axes. Here, I asked to what extent and along what axes are ant-plant protection interactions, in which plants provide rewards for ants that in turn defend plants from herbivores, context dependent. First, a meta-analytic summary of published studies on ant-plant protection interactions revealed that interaction outcomes are on average mutualistic, and context dependency occurred due to plant reward type (domatia vs food bodies vs extrafloral nectaries), ant species richness, and latitude. Second, in a case study in the Sonoran Desert, extrafloral nectar production caused context dependent mutualistic and antagonistic ant-plant interactions, despite largely commensalistic interaction outcomes. These results suggest some ecological axes resulting in context dependency in mutualisms.