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Thesis (M.S.)--Eastern Illinois University, 2010. / Includes bibliographical references (leaves 24-29).

Despite a number of recent studies focused on the issue, patterns of stream insect dispersal in temperate streams of North America remain poorly understood. Movement of benthic invertebrates is notoriously difficult to measure directly using traditional means; however, genetic markers provide an ideal method for estimating stream insect dispersal. In this study, the control region of mitochondrial DNA was used to study gene flow and dispersal among populations of the stonefly <i>Peltoperla tarteri</i> in the Southern Appalachians. The control region of <i>P. tarteri</i> is approximately 1270 base pairs (bp) in length, 81% AT-rich, and contains variable numbers of a 74 bp tandem repeat containing the sequence motif "5'-GGGGGC-3". Many stream insects have long life cycles that result in the simultaneous existence of multiple cohorts throughout the larval development period. If larval development is fixed, genetic isolation among cohorts may confound genetic estimates of dispersal. Although larval head width data indicated that <i>P. tarteri</i> is semivoltine in southwestern Virginia, low levels of genetic differentiation among cohorts suggested that larval development of <i>P. tarteri</i> is not fixed and that some individuals complete development in one or three years rather than two. This 'cohort splitting' would result in individuals from distinct cohorts maturing at the same time and mating with one another. Such developmental plasticity may allow some individuals to avoid adverse environmental conditions. The extent and likely mechanism of dispersal was determined by comparing levels of population genetic differentiation within drainages to that among drainages. While there was no consistent relationship between genetic and geographic distance, genetic differentiation was generally high within and among drainages. Nested clade analysis indicates that historical fragmentation and range expansion coupled with contemporary gene flow explain the present day pattern of genetic variation in <i>P. tarteri.</i> In order for these historical patterns to have such a strong influence on present day genetic structure, both larval and adult dispersal must be restricted. However, the genetic data suggest that larval dispersal is more frequent than adult dispersal. / Ph. D.

The purpose of the present study was to investigate how plant spatial patterns and insect behavior interact to influence the population dynamics of insects using the plants. The study included three phases: l) field experiments using collards (Brassica oleracea) and the crucifer insect fauna; 2) simulation models representing the population dynamics of an insect herbivore as functions of insect dispersal behavior and host plant patch size; and 3) model-field syntheses integrating model predictions and field variability estimates to choose an appropriate spatial scale for future field experiments or applications. In field experiments on surrounding plant type, collards were planted with 1) other collards; 2) collards treated with a systemic insecticide; 3) broccoli, a related host; and 4) tomatoes, an unrelated host whose odor may repel crucifer pests. In three such experiments, eggs and larvae of the imported cabbageworm (Pieris rapae (L.)) were most abundant an collards surrounded by tomatoes. These results were contrary to those from previous experiments with other crucifer pests, but can perhaps be explained by P. rapae's preference for ovipositing on isolated host plants. In three patch size experiments, P. rapae eggs and larvae were more abundant on collards in small patches; in one of these experiments, the diamondback moth (Plutella xylostella (Linn.)) was more abundant in large patches. The results for P. rapae were consistent with previous studies showing more oviposition on plants in smaller patches and on plants at the edge of a patch. The simulation models predicted mean level and variability of an insect herbivore population based on interactions between insect behavior and host plant patch size. Features of insect behavior modeled were: 1) an inverse relationship between distance and dispersal; 2) preferences for host vs. nonhost plants, which differ for generalist and for specialist herbivores; and 3) preference of specialists for larger areas of host plants. Aspects of plant pattern studied were size and number of host plant patches in a background of nonhost vegetation. Constant, exponential and logistic growth of insect populations in the nonhost background and in the host patches were used. The models were designed to provide a theoretical framework for studying interactions between insect behavior and plant pattern, not to duplicate the dynamics of the field system. However, for the model-field syntheses, parameters of one model were fit to field data to establish a correspondence between expected differences in population levels predicted by the model and variability estimates obtained in the field experiments. The fitted model was used to construct a graph of differences in population levels versus patch size. Field variability estimates were used to calculate the least difference in population levels, for a given number of replicates and subsamples, that could be detected in field experiments. The least difference was compared with the differences predicted b y the fitted model to determine what patch sizes will produce significant effects of patch size on insect populations. This method was used to assess feasibility of future field experiments and to select appropriate patch sizes. The method can also be used to evaluate crop field size in agroecosystems as a component of pest management.

Orientadores: Ana Maria Lima de Azeredo-Espin, Louis Bernard Larczko / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-12T11:37:35Z (GMT). No. of bitstreams: 1 Lyra_MarianaLucio_D.pdf: 5356406 bytes, checksum: f0e53a7a9c5d9317cf06c336aa13d1f4 (MD5) Previous issue date: 2008 / Resumo: A mosca da bicheira, Cochliomyia hominivorax, é um ectoparasita de animais de sangue quente endêmico da região Neotropical, responsável por causar graves prejuízos à pecuária. Nesta tese, diferentes aspectos da variação molecular e morfológica da espécie foram abordados com o objetivo de se obter um cenário mais amplo sobre a extensão e distribuição da diversidade genética em C. hominivorax. As principais contribuições da tese estão compiladas em duas partes. Uma delas trata da diversidade do DNA mitocondrial (DNAmt) da espécie e está dividida em 4 trabalhos. O primeiro (Artigo 1) trata da diversidade genética e estrutura de populações no Uruguai; os resultados sugerem que as populações nessa localidade são panmíticas e polimórficas com relação ao DNAmt. O segundo trabalho (Artigo 2) apresenta um estudo da distribuição da diversidade mitocondrial em 34 populações de 10 diferentes países, desde o Caribe até o Uruguai. Na região do Caribe foi identificada alta estruturação populacional e baixos índices de diversidade, enquanto que na América do Sul foi identificada alta diversidade e baixa estruturação populacional. Os resultados revelaram um padrão complexo para a distribuição da diversidade genética, sugerindo que diferentes processos estão atuando na formação e manutenção do padrão observado. O terceiro trabalho desta parte trata da caracterização da variação de tamanho da região controle do DNAmt, identificada em alguns indivíduos da espécie; essa variação se deu por repetições em série dos blocos de seqüência conservada e parece ter surgido de forma independente em cada localidade. A análise do domínio B da região controle sugere que este pode ser um potencial marcador para análise de populações, uma vez que revelou grande polimorfismo intra-específico. O quarto trabalho investiga a relação entre as amostras de diferentes regiões do Caribe e América continental por seqüenciamento do gene COII; os resultados sugerem que as populações de Cuba são bem diferenciadas e que as populações do Caribe podem ser originadas de diferentes eventos de colonização. A outra parte das contribuições desta tese é formada por dois trabalhos e trata da caracterização da variação morfológica da asa. O primeiro deles (Artigo 3) caracteriza a variação morfológica de asas de C.hominivorax entre sexos e localidades. Foi identificado um grande dimorfísmo sexual na espécie para tamanho e forma da asa, sugerindo a existência de diferentes pressões seletivas em cada sexo. Também foram identificadas variações entre as populações analisadas, que não estão correlacionadas com as diferenças de latitude e temperatura, sugerindo que diferentes características das localidades, dos hospedeiros ou eventos históricos podem influenciar na variação das asas. O segundo trabalho dessa parte apresenta uma comparação de morfologia da asa entre as espécies C. hominivorax e C. macellaria. Os resultados indicam que análises de morfometria geométrica podem ser utilizadas para identificação das espécies, sendo essa abordagem uma estratégia para a rápida identificação de C. hominivorax e monitoramento de eventos de invasão desta espécie em áreas onde foi erradicada. Os resultados obtidos nos dois trabalhos dessa parte demonstram que a variação da asa é um potencial marcador para estudo de variação morfológica entre populações da mosca da bicheira e entre espécies do gênero Cochliomyia / Abstract: The New World screwworm fly, Cochliomyia hominivorax, is an important parasitic insect pest in Neotropical region, and represents a serious threat to the livestock sector. In this thesis we analyzed different aspects of molecular and morphological variation in the species, aiming to obtain a clear scenario about the extent and distribution of genetic diversity in C. hominivorax. The main contributions of this thesis are organized in two parts. The first one, composed of four different works, contains the results about mitochondrial DNA (mtDNA) diversity in the species. In the first work (Article 1), mtDNA was used to study the diversity and population structure of C. hominivorax in Uruguay; results indicated high mtDNA variability and suggested that in Uruguay species form a single panmitic population. In the second work (Article 2) we analyzed 34 populations of C. hominivorax in ten different countries of Caribbean and South America, encompassing almost all the current distribution of the species. Significant population structure and low variability were found in Caribbean populations; in contrast, high variability and low differentiation was found among mainland populations. Our results showed a complex pattern of population genetic structure for the species, suggesting that different processes are acting to the shaping and maintenance of the observed patterns. The third work in this part is about the characterization of length variation in the mtDNA control region; the variation was due to the existence of tandem repetitions of conserved sequence blocks in the control region and the observations suggested that repetitions may be independent events in each locality. The analysis of variable domain revealed high intra-specific polymorphism and suggested that this region may be a potential marker for the study of species populations. The fourth work analyses the relationship between Caribbean and mainland population; Cuban populations differs significantly from all others results suggested different colonization events for Caribbean region. The other part of this thesis consists of two works about characterization of wing variation. The first one (Article 3) provides a morphological analysis of wing variation of C. hominivorax and evaluate the potential use of this morphological character for population variation studies. We found a striking sexual dimorphism in the species for both wing size and shape and suggested that it reflects a history of different selection pressures operating on males and females. We also found morphological variation between populations, which were not associated with latitude or temperature; these preliminary results suggested that C. hominivorax morphology might be affected by locality and/or host characteristics. The second work is about wing variation between C. hominivorax and C. macellaria, results indicated that geometric morphometric methods are useful for species identification and that this strategy could be useful in monitoring invasions events in regions where species have been previous eradicated. Results of this part indicated that wing shape and size may be a reliable marker for population analyses of New World Screwworm, and for inter-specific analyses in genus Cochliomyia. / Doutorado / Genetica Animal e Evolução / Doutor em Genetica e Biologia Molecular

<p dir="ltr">Specialty crop growers in the Great Lakes region of the United States and Canada have been struggling for decades to manage the carrot weevil (<i>Listronotus oregonensis</i>). In carrot, parsley, and celery production, growers may experience 40-100% yield loss, despite the intensive use of insecticides (Boivin, 1999; Jasinski, 2008; Telfer et al., 2019). To improve sustainable management of this native pest in commercial vegetable production, we must address existing knowledge gaps in carrot weevil mate-finding behavior, population genetic diversity and gene flow, and grower adoption and efficacy of integrated pest management (IPM) strategies, like cultivar selection, to combat this pest. To date, these factors have not been evaluated in the carrot weevil system, yet together they have significant implications for developing novel monitoring tools, grower decision making, and the potential evolution of insecticide resistance in this damaging pest.</p><p dir="ltr">To address knowledge gaps in grower adoption and the efficacy of IPM strategies, such as cultivar selection, I investigated the influence of carrot cultivar on the oviposition preference of carrot weevil in the laboratory and quantified the diversity of insect assemblages on carrots in Ohio and Indiana. In tandem, I delivered an online survey to specialty crop growers in Indiana and Ohio to measure their knowledge and use of insect-resistant cultivars as a part of an IPM strategy. I found that carrot cultivar did not impact carrot weevil oviposition preference, but rather the number of petiole trichomes was positively correlated with the cumulative number of egg scars found on a given carrot cultivar. Similarly, cultivar did not influence the diversity of insect assemblages associated with carrot foliage, but hemipterans were the dominant group found across cultivars. Moreover, insect diversity across all carrot cultivars was high, with Shannon-Weiner diversity indices ranging from 2.14 to 2.45.</p><p dir="ltr">I analyzed survey responses from vegetable growers regarding their knowledge, current use, and future use of insect-resistant cultivars and found no significant differences between conventional or organic growers, in either Indiana or Ohio, or across experience levels regarding their knowledge and current or future use of insect-resistant cultivars. Although a greater number of organic growers were aware of insect-resistant cultivars, they were not incorporated into their IPM plans. In contrast, half of responding conventional growers indicated implementing insect-resistant cultivars in current IPM plans. Growers indicated that more information about the efficacy, costs, and benefits of insect-resistant vegetable cultivars would be most helpful in informing their decision to incorporate this IPM tactic on their farms.</p><p dir="ltr">To address knowledge gaps regarding carrot weevil mate-finding behavior, I investigated behavioral response to conspecific frass using Y-tube bioassays and the volatiles of frass samples were analyzed using gas-chromatography mass-spectrometry (GC-MS) as starting points to assess the presence of volatile chemical cues that might function as sex or aggregation pheromones. I found that male and female weevils oriented strongly towards volatiles from male frass. However, conspecifics were not attracted to mixed or female frass, suggesting male frass contains behaviorally relevant chemical cues that are unique or present in greater abundance than in female frass. When I analyzed the chemical abundance and composition of the male frass volatiles, I found 16 common compounds across all samples and no compounds were unique to the male volatile blend. Specifically, (1S)-6,6-dimethyl-2-methylene-Bicyclo[3.1.1]heptane and (1R)-2,6,6-Trimethylbicyclo[3.1.1]hept-2-ene were present in significantly higher abundance in extracts of males frass compared to those of female frass.</p><p dir="ltr">Finally, to address knowledge gaps in the genetic diversity and gene flow of carrot weevil populations in the Great Lakes Region of the U. S., I used single nucleotide polymorphisms (SNPs) to compare genetic diversity and structure of agricultural populations of carrot weevil in Michigan and Ohio. I found limited genetic differentiation between three carrot weevil populations collected from celery and parsley fields located in Michigan and Ohio. I also found high inbreeding coefficients and heterozygote deficiency in all populations, suggesting that all carrot weevil populations are locally confined. These results suggest significant gene flow between populations, which has implications for management, specifically the mitigation and management of insecticide resistance.</p><p dir="ltr">Together, the results from my dissertation can be applied to the improvement of carrot weevil IPM across the Great Lakes region of the United States and Canada. Further investigations into the impact of physical characteristics, specifically petiole trichomes, on carrot weevil oviposition behavior can inform the breeding and development of resistant carrot cultivars. Results from my behavioral bioassay studies represent a critical first step towards the identification of an aggregation or sex pheromone, which would greatly improve detection of resident carrot weevil populations when used in conjunction with current monitoring traps. My results also suggest that monitoring and mitigation of insecticide resistance in carrot weevil populations should be considered at the regional scale, at minimum, with significant gene flow between carrot weevil populations within the Great Lakes Region.</p>

Chromolaena odorata (L.) King and Robinson (chromolaena, triffid weed) (Asteraceae: Eupatorieae) is one of the most problematic weeds in the subtropical northeastern parts of South Africa. Calycomyza eupatorivora Spencer (Diptera: Agromyzidae) was introduced as a biological control agent for the control of this weed. No study has yet been done to quantify field populations of C. eupatorivora since its establishment in 2003. The aim of this study was therefore to measure aspects of the field population and laboratory behaviour of C. eupatorivora on C. odorata. The first objective was to determine the percentage leaf area mined by larvae of C. eupatorivora on C. odorata plants exposed to three densities of mated flies, and also to determine the number of mines produced by these different densities, and their distribution on the plant. It also attempts to determine the relationship between chromolaena leaf quality and usage by C. eupatorivora. The maximum percentage of leaf area damaged was 37.5% for one of the trials involving five pairs of flies. Mean percentage leaf area damaged was slightly higher with five (28.5%) than ten pairs (22.0%) of adults and was lowest with one pair (6.5%), but these differences were not significant. In relation to the mean number of mines per plant, five and ten pairs of flies caused slightly more mines than one pair. The other significantly different parameter was number of leaves mined per plant, which was higher for five pairs. Within a plant, C. eupatorivora probably selects a subset of leaves with certain chemical and physical characteristics for oviposition since certain leaves were left unmined while others received multiple eggs. Percentage water content did not differ between mined and unmined leaves, but clear patterns were shown by acid detergent lignin which was higher in unmined leaves and nonstructural carbohydrates which were much higher in mined leaves. It is likely that leaf age plays a role in its suitability. The second objective was to quantify C. eupatorivora infestation levels, by counting and examining larval leaf mines, on C. odorata in the field at four times ('seasons' - September, December, March and July) over a 12-month period, and at three study sites that each included two habitats, viz. open and shady. At each of these six sampling sites, line transects were laid out and plants/branches sampled along them. Both plant/branch height and the number of leaves increased between September and March, and plants in the open habitats were taller and had more leaves than those in the shaded habitats. At the third site, the shady habitat supported taller plants with more leaves compared to the same habitat at the other sites. There was a steep increase in the number of C. eupatorivora mines from December to March. The mean number of mines, both total and in relation to leaves available, was highest in March, and was higher in the shaded habitats compared to the open habitats. The mean number of mines per damaged leaf was slightly higher in December compared to the other seasons, and was also higher in the open than the shaded habitats. Mean larval mortality was high (70%) in September but decreased to 32% in December, and increased again in late summer. The overall levels of mining by C. eupatorivora were low, with less than 5% of leaves sampled having mines. Taken together, the laboratory and field trials suggest that C. eupatorivora is restricted to a subset of the leaves of C. odorata for its development; that the field population is unable to make full use of the resource of young, palatable leaves that develop in early- to mid-summer because it only becomes large in late summer; and that the high mortality rate of young larvae negatively affects both the population of the fly and the level of damage to the plant. Given that these results were obtained in an area where the population of C. eupatorivora is relatively high, it is unlikely that the fly is having anything more than a negligible effect on C. odorata in South Africa at present. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.