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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Foraging-predator avoidance trade-offs made by migrant and resident elk (Cervus elaphus) on their sympatric winter range

Robinson, Barry Glen Unknown Date
No description available.
22

Grain-dependent habitat selection in white-tailed deer (Odocoileus virginianus)

2014 October 1900 (has links)
A fundamental problem in ecology is determining what factors affect the distribution of organisms across a landscape. Landscapes are by their nature heterogeneous and different habitat types confer different fitness benefits and costs to organisms that inhabit them. Ecologists are now aware of the importance of examining multiple spatial scales when designing studies quantifying animal resource selection. Scale of analysis has been shown to be important, since ecological pressures relating to the establishment of a home range differ from those relating to the use of resources within the home range. Most studies that examine multiple spatial scales examine the effect of modifying extent. Here, I examine the role of grain, an underappreciated component of scale, on our interpretation of habitat selection patterns and functional response. The goal of this thesis was to examine how grain size affects the interpretation of animal resource selection and functional response across multiple habitats. The perceptual range of an individual is known to change with habitat, therefore I hypothesized that resource selection and functional response would be both grain- and habitat-dependent, and that resource selection functions computed using different grains for different resources would be more predictive than models computed using only a single grain. I used GPS-collared white-tailed deer (Odocoileus virginianus) to quantify resource selection functions at various grains and used generalized linear mixed effects modelling and multi-model inference techniques to examine how resource selection patterns changed with spatial scale across habitat types. I used selection ratios to examine functional response across grains. Model coefficients changed with grain and the strength of selection varied by habitat type. Multi-grain resource selection functions had lower AIC values and better cross-validation scores than single grain models. Functional response varied with scale and habitat type, displaying a unique relationship for each habitat. My results suggest that spatial memory and habitat-dependent perceptual range play an important role in resource selection. I conclude that the examination of multiple grains in the study of animal habitat selection and functional response represents a step forward in our ability to understand what drives the distribution and abundance of organisms.
23

Foraging-predator avoidance trade-offs made by migrant and resident elk (Cervus elaphus) on their sympatric winter range

Robinson, Barry Glen 11 1900 (has links)
Migratory behaviour of the Ya Ha Tinda (YHT) elk population is diminishing while the number of residents remaining on the YHT winter range year-round is increasing. Previous research addressing the fitness consequences of each migratory strategy assumed there was no advantage to either segment when they shared the YHT winter range. In testing this assumption, I found no spatial segregation of migrant and resident home-ranges during winter. Both groups were exposed to similar forage resources and residents were exposed to higher night-time, but not day-time predation risk. Residents were better than migrants at reducing the foraging costs of vigilance and increased vigilance in areas of high wolf predation risk, but not near human activity because of habituation. Migrants were not habituated to humans and exhibited more constant vigilance regardless of spatial variations in risk. My results do not support the previous assumption. Instead, I found residents may be at an advantage on the winter range while forage is abundant and no snow is present. / Ecology
24

Desempenho de leucochrysa sp. (Neuroptera Chrysopidae) em diferentes presas e sua seletividade a produtos fitossanitários / Performance of Leucochrysa sp. (Neuroptera: Chrysopidae) on different prey and theselectivity of phytosanitary products

Costa, Simone Silva da 19 December 2016 (has links)
Green lacewings (Neuroptera: Chysopidae) are predatory insects with potential to be used in biological control programs of agricultural pests. This work aimed to evaluate the biological aspects of Leucochrysa sp. on different prey species and to verify the selectivity of phytosanitary products.The bioassays were conducted in climatized rooms regulated to a temperature of 25 ± 2 °C, 70 ± 10% R.H. and 12h photophase. The insects were individualized in rectangular boxes of 220 mL until the adult emergence. The duration and viability of larval instars and pupal period were evaluated. The formed couples (n = 20) were kept in PVC cages internally coated with sulphite paper. A period of 120 days was established to evaluate the fecundity and fertility of females.The predator had its best performance when fed with eggs, nymphs and pupae of Aleurocanthuswoglumi Ashby, 1915 (Hemiptera: Aleyrodidae); nymhs and adults of Toxopteracitricida (Kirkaldy, 1907) (Hemiptera: Aphididae) and Brevicorynebrassicae (Linnaeus, 1758) (Hemiptera: Aphididae), respectively, whose larval-adult duration ranged from 34.00 to 37.77 days. When submitted to eggs, nymphs and pupae of Aleurodicusmagnificus Costa Lima, 1928 (Hemiptera: Aleyrodidae) as food source, the green lacewing did not complete its cycle.Regarding the polynomial regression analyzes performed to investigate the functional response patterns on the aphids B. brassicae and T. citricida, a type II response was revealed for the second and third instar of the predator, which is represented by an asymptotic curve, in which the predator is increasing the prey consumption until saturation occurs. The functional response pattern was not altered by the influence of different prey stages used in this study.In the IPM the use of agrochemicals should be performed when they present some type of selectivity, thus, Neem based products were evaluated upon eggs and larvae of second and third instars of Leucochrysa sp. The insects were kept in Petri dishes, sprayed and individually transferred to plastic boxes until adult emergence. The larvae were fed with eggs of Anagastakuehniella(Zeller, 1879) (Lepidoptera: Pyralidae). The formed couples (n = 15) from treated eggs, were fed with beer yeast and honey (1: 1).Azamax®; Nim-I-Go® and Emulzinim® were classified as harmless; Ethanolic extract of neem and NeenMax® as slightly harmful, when sprayed on eggs of the predator. Azamax®; Nim-I-Go®, Emulzinim® and Ethanolic extract of neem were classified as harmless when applied to second and third instar larvae. Deltamethrin was considered harmful to eggs and second instar larvae and moderately harmful to third instar larvae. / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Os crisopídeos (Neuroptera: Chysopidae) são insetos predadores com o potencial de serem utilizadas em programas de controle biológico de pragas agrícolas. Este trabalho teve como objetivo avaliar os aspectos biológicos de Leucochrysa sp. sobre diferentes presas e verificar sua seletividade a produtos fitossanitários. Os bioensaios foram conduzidos em salas climatizadas regulada a uma temperatura de 25±2°C, U.R. de 70±10% e 12 horas de fotofase. Os insetos foram individualizados em caixas retangulares de 220 mL, onde permaneceram até adultos. Foi avaliada duração e viabilidade dos ínstares larval e período pupal. Os casais formados (n=20) foram acondicionados em gaiolas de PVC revestidas internamente com papel sulfite. Para avaliar a fecundidade e fertilidade das fêmeas, foi estabelecido um período de 120 dias. O predador teve seu melhor desempenho quando alimentado com ovos, ninfas e pupas de Aleurocanthus woglumi Ashby, 1915 (Hemiptera: Aleyrodidae); ninfas e adultos de Toxoptera citricida (Kirkaldy, 1907) (Hemiptera: Aphididae) e Brevicoryne brassicae (Linnaeus, 1758) (Hemiptera: Aphididae), respectivamente, cuja duração larva-adulto variou de 34,00 a 37,77 dias. Quando submetidos a ovos, ninfas e pupas de Aleurodicus magnificus Costa Lima, 1928 (Hemiptera: Aleyrodidae) como fonte de alimento o crisopídeo não completou seu ciclo. Em relação às análises de regressão polinomial realizadas para investigar os padrões de resposta funcional sobre os pulgões B. brassicae e T.citricida, foi revelado para o segundo e terceiro ínstares do predador uma resposta tipo II, que é representada por uma curva assintótica, na qual o predador vai aumentando o consumo de presas até o momento em que ocorre a saturação. O padrão de resposta funcional não foi alterado sob a influência das diferentes presas nas fases utilizadas neste estudo. Sabendo-se que no MIP o uso de agrotóxicos deve ser feito quando apresentarem algum tipo de seletividade, foram avaliados produtos a base de nim sobre ovo e larvas de segundo e terceiro ínstares de Leucochrysa sp. Os insetos foram acondicionados em placa de Petri, pulverizados e transferidos individualmente para caixas plásticas até a emergência dos adultos. As larvas foram alimentadas com ovos de Anagasta kuehniella (Zeller, 1879) (Lepidoptera: Pyralidae). Os casais formados (n=15) apartir de ovos tratados foram alimentados com levedo de cerveja e mel (1:1). Azamax®; Nim-I-Go® e Emulzinim® foram classificados como inócuos; Extrato etanólico de nim e NeenMax® como levemente nocivos, quando estes foram pulverizados sobre ovos do predador. Enquanto que Azamax®; Nim-I-Go®, Emulzinim® e Extrato etanólico de folhas nim foram classificados como inócuos quando aplicados em larvas de segundo e terceiro instares. Deltametrina foi considerado nocivo a ovos e larvas de segundo ínstar e moderadamente nocivo às larvas de terceiro instar.
25

Características biológicas de Orius insidiosus alimentado com Aphis gossypii em algodão transgênico e convencional

Veiga, Ana Carolina Pires [UNESP] 21 February 2011 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:25:19Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-02-21Bitstream added on 2014-06-13T18:26:16Z : No. of bitstreams: 1 veiga_acp_me_jabo.pdf: 533606 bytes, checksum: dcd2d426b9ebf8716c033191213bd5ea (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O objetivo deste trabalho foi avaliar as características biológicas e taxa de predação de Orius insidiosus tendo como presa ninfas de terceiro/quarto estádio de Aphis gossypii sobre as variedades de algodoeiro transgênica NuOPAL (Bollgard I Evento 531) e convencional Buriti. Para avaliar a duração e a sobrevivência de cada estádio ninfal e as características reprodutivas de fêmeas e longevidade dos adultos foram individualizadas 60 ninfas recém-eclodidas em placas de Petri contendo um pedaço de algodão (aproximadamente 1 cm2) umedecido com água destilada, um pedaço de papel sulfite branco (0,5 cm2) para servir como refúgio e pulgões A. gossypii de terceiro/quarto instar como presas. Para estudar o comportamento de predação, fêmeas de O. insidiosus com idade entre 12-24h foram individualizadas em placas de Petri. Os testes foram conduzidos empregando-se as densidades de 2, 4, 8, 16 e 32 ninfas de A. gossypii para cada variedade de algodão. O período e a viabilidade ninfal de O. insidiosus foram semelhantes nas duas variedades. O número de ovos por fêmeas, viabilidade de ovos, longevidade de macho e fêmeas foram semelhantes nas duas variedades. O tempo de manipulação (h) e a taxa de ataque (h-1) foram respectivamente de 0,0697 (h) e 1, 1862 ( h-1) para a variedade Buriti e 0,0713 (h) e 0,3030 h-1 para NuOPAL. As variedades Buriti e NuOPAL não afetaram as características biológicas do período ninfal de O. insidiosus alimentado com A. gossypii porém prejudica significativamente o potencial reprodutivo do predador. Na variedade Buriti O. insidiosus apresenta maior taxa de ataque. O número médio de presas consumidas por O.insidisous é semelhante nas variedades Buriti e NuOPAL em 24 horas e nas maiores densidades. A. gossypii não é substrato ideal para O. insidiosus / The aim of this study was to evaluate the biological characteristics and predation rate of Orius insidiosus using third and fourth instar Aphis gossypii as prey on transgenic cotton variety NuOPAL (Bollgard I Event 531) and conventional variety Buriti. To evaluate the duration and survival of each nymphal stage and the reproductive characteristics of females and longevity of adults were individually newly hatched nymphs 60 in Petri dishes containing a piece of cotton (approximately 1 cm 2) moistened with distilled water, a piece of paper white bond (0.5 cm2) to serve as a refuge and aphids A. gossypii third / fourth instar as prey. To study the behavior of predatory, females of O. insidiosus aged between 12-24h were isolated in Petri dishes. The tests were conducted using the densities of 2, 4, 8, 16 and 32 nymphs of A. gossypii for each variety of cotton. The period and nymphal O. insidiosus were similar in both variety. The number of eggs per female, egg viability, longevity of males and females were similar in both varieties. The handling time (h) and attack rate (h-1) were respectively 0.0697 (h) and 1, 1862 (h-1) for a variety Buriti and 0.0713 (h) and 0.3030 (h-1) for NUOPAL. Variety Buriti and NuOPAL did not affect the biological characteristics of nymphal O. insidiosus fed A. gossypii but significantly affect the reproductive potential of predador. In the variety Buriti O. insidiosus has a higher attack rate. The type of functional response shown by females of the predator was type II in both varieties. The average number of prey consumed by O.insidisous is similar in varieties Buriti and NuOPAL in 24 hours and at higher densities. A. gossypii is not ideal substrate for O. insidiosus
26

Optimal Design of Experiments for Functional Responses

January 2015 (has links)
abstract: Functional or dynamic responses are prevalent in experiments in the fields of engineering, medicine, and the sciences, but proposals for optimal designs are still sparse for this type of response. Experiments with dynamic responses result in multiple responses taken over a spectrum variable, so the design matrix for a dynamic response have more complicated structures. In the literature, the optimal design problem for some functional responses has been solved using genetic algorithm (GA) and approximate design methods. The goal of this dissertation is to develop fast computer algorithms for calculating exact D-optimal designs. First, we demonstrated how the traditional exchange methods could be improved to generate a computationally efficient algorithm for finding G-optimal designs. The proposed two-stage algorithm, which is called the cCEA, uses a clustering-based approach to restrict the set of possible candidates for PEA, and then improves the G-efficiency using CEA. The second major contribution of this dissertation is the development of fast algorithms for constructing D-optimal designs that determine the optimal sequence of stimuli in fMRI studies. The update formula for the determinant of the information matrix was improved by exploiting the sparseness of the information matrix, leading to faster computation times. The proposed algorithm outperforms genetic algorithm with respect to computational efficiency and D-efficiency. The third contribution is a study of optimal experimental designs for more general functional response models. First, the B-spline system is proposed to be used as the non-parametric smoother of response function and an algorithm is developed to determine D-optimal sampling points of a spectrum variable. Second, we proposed a two-step algorithm for finding the optimal design for both sampling points and experimental settings. In the first step, the matrix of experimental settings is held fixed while the algorithm optimizes the determinant of the information matrix for a mixed effects model to find the optimal sampling times. In the second step, the optimal sampling times obtained from the first step is held fixed while the algorithm iterates on the information matrix to find the optimal experimental settings. The designs constructed by this approach yield superior performance over other designs found in literature. / Dissertation/Thesis / Doctoral Dissertation Industrial Engineering 2015
27

Características biológicas de Orius insidiosus alimentado com Aphis gossypii em algodão transgênico e convencional /

Veiga, Ana Carolina Pires. January 2011 (has links)
Resumo: O objetivo deste trabalho foi avaliar as características biológicas e taxa de predação de Orius insidiosus tendo como presa ninfas de terceiro/quarto estádio de Aphis gossypii sobre as variedades de algodoeiro transgênica NuOPAL (Bollgard I Evento 531) e convencional Buriti. Para avaliar a duração e a sobrevivência de cada estádio ninfal e as características reprodutivas de fêmeas e longevidade dos adultos foram individualizadas 60 ninfas recém-eclodidas em placas de Petri contendo um pedaço de algodão (aproximadamente 1 cm2) umedecido com água destilada, um pedaço de papel sulfite branco (0,5 cm2) para servir como refúgio e pulgões A. gossypii de terceiro/quarto instar como presas. Para estudar o comportamento de predação, fêmeas de O. insidiosus com idade entre 12-24h foram individualizadas em placas de Petri. Os testes foram conduzidos empregando-se as densidades de 2, 4, 8, 16 e 32 ninfas de A. gossypii para cada variedade de algodão. O período e a viabilidade ninfal de O. insidiosus foram semelhantes nas duas variedades. O número de ovos por fêmeas, viabilidade de ovos, longevidade de macho e fêmeas foram semelhantes nas duas variedades. O tempo de manipulação (h) e a taxa de ataque (h-1) foram respectivamente de 0,0697 (h) e 1, 1862 ( h-1) para a variedade Buriti e 0,0713 (h) e 0,3030 h-1 para NuOPAL. As variedades Buriti e NuOPAL não afetaram as características biológicas do período ninfal de O. insidiosus alimentado com A. gossypii porém prejudica significativamente o potencial reprodutivo do predador. Na variedade Buriti O. insidiosus apresenta maior taxa de ataque. O número médio de presas consumidas por O.insidisous é semelhante nas variedades Buriti e NuOPAL em 24 horas e nas maiores densidades. A. gossypii não é substrato ideal para O. insidiosus / Abstract: The aim of this study was to evaluate the biological characteristics and predation rate of Orius insidiosus using third and fourth instar Aphis gossypii as prey on transgenic cotton variety NuOPAL (Bollgard I Event 531) and conventional variety Buriti. To evaluate the duration and survival of each nymphal stage and the reproductive characteristics of females and longevity of adults were individually newly hatched nymphs 60 in Petri dishes containing a piece of cotton (approximately 1 cm 2) moistened with distilled water, a piece of paper white bond (0.5 cm2) to serve as a refuge and aphids A. gossypii third / fourth instar as prey. To study the behavior of predatory, females of O. insidiosus aged between 12-24h were isolated in Petri dishes. The tests were conducted using the densities of 2, 4, 8, 16 and 32 nymphs of A. gossypii for each variety of cotton. The period and nymphal O. insidiosus were similar in both variety. The number of eggs per female, egg viability, longevity of males and females were similar in both varieties. The handling time (h) and attack rate (h-1) were respectively 0.0697 (h) and 1, 1862 (h-1) for a variety Buriti and 0.0713 (h) and 0.3030 (h-1) for NUOPAL. Variety Buriti and NuOPAL did not affect the biological characteristics of nymphal O. insidiosus fed A. gossypii but significantly affect the reproductive potential of predador. In the variety Buriti O. insidiosus has a higher attack rate. The type of functional response shown by females of the predator was type II in both varieties. The average number of prey consumed by O.insidisous is similar in varieties Buriti and NuOPAL in 24 hours and at higher densities. A. gossypii is not ideal substrate for O. insidiosus / Orientador: Sergio Antonio De Bortoli / Coorientador: Antonio Carlos Busoli / Banca: Ricardo Antonio Polanczyk / Banca: José Ednilson Miranda / Mestre
28

Factors Affecting Elicitation of Vocal Response from Coyotes and Population-Level Response to a Pulsed Resource Event

Petroelje, Tyler Robert 17 August 2013 (has links)
Long-distance vocalizations by canids play an important role in communication among individuals. I evaluated efficacy of broadcasted coyote (Canis latrans) group-yip calls and gray wolf (C. lupus) lone howls to elicit vocal responses from 18 GPS-collared coyotes on 144 occasions. I concluded that eliciting coyote vocalizations where wolves are present will not bias responses, and recommend eliciting coyote vocalizations using recorded coyote group-yip howls during July–September to estimate species’ presence or density. From foraging theory, generalist predators should increase consumption of prey if prey availability increases. I estimated densities for coyotes, adult deer, and fawns, and collected coyote scat to estimate occurrence and biomass of adult and fawn deer consumed by coyotes during 2 periods. I suggest that consumption rates of coyotes was associated positively with increases in fawn density, and fawn consumption by coyotes follows predictions of foraging theory during this pulsed resource event.
29

Effet de la température sur les interactions trophiques et intraguildes au sein d’un système plante-herbivore-ennemis naturels : modélisation et approches expérimentales

Sentis, Arnaud 03 1900 (has links)
Doctorat réalisé en cotutelle entre l'Université de Montréal et l'Université Paul Sabatier-Toulouse III / Il est maintenant reconnu que les changements climatiques ont des impacts importants sur l’ensemble des organismes vivants. Parmi les facteurs de ces changements, la température occupe une place prépondérante pour les organismes ectothermes car elle régule leur métabolisme. Toutefois, bien que les effets de la température sur les individus d’une espèce soient largement connus, les connaissances demeurent limitées quant aux conséquences sur les interactions trophiques. Dans ce contexte, notre étude s’intéresse aux effets de la température sur un système biologique composé d’une plante, le poivron Capsicum annuum L., d’un herbivore, le puceron Myzus persicae Sulzer (proie extraguilde), ainsi que de deux de ses ennemis naturels : la coccinelle maculée Coleomegilla maculata lengi Timberlake (prédateur intraguilde) et la cécidomyie prédatrice Aphidoletes aphidimyza Rondani (proie intraguilde). Dans ce but, nous avons opté pour une approche multiple comprenant : (1) la modélisation des interactions prédateur-proie et intraguilde (prédation entre deux compétiteurs d’espèces différentes qui exploitent une même ressource), (2) la réalisation d’expériences empiriques en laboratoire permettant de tester les prédictions des modèles et de caractériser l’effet de la température et de ses variations sur les composantes du système biologique étudié. Conformément aux prédictions d’un premier modèle, nous mettons en évidence que, lorsque la température augmente, C. maculata est plus efficace pour trouver et manipuler ses proies, ce qui augmente le taux de prédation. En revanche, à haute température son efficacité de recherche décroît, ce qui entraîne une diminution du taux de prédation. L’activité de prédation se limite donc à une fenêtre thermique en dehors de laquelle elle est réduite ou nulle. Par la suite, nous comparons un modèle linéaire et un modèle non-linéaire (saturant à haute densité de proies) afin de déterminer lequel de ces deux modèles décrit le mieux la réponse fonctionnelle d’un prédateur intraguilde, c’est-à-dire la relation entre le nombre de proies consommées et la densité de proies. Nos résultats expérimentaux démontrent que les prédictions du modèle non-linéaire correspondent bien aux observations empiriques, tandis que le modèle linéaire surestime largement le nombre de proies consommées et la fréquence des interactions intraguildes. Par la suite, nous dérivons le modèle non-linéaire afin d’y inclure l’effet de la température. Comme prédit par ce dernier modèle, la prédation intraguilde devient plus fréquente lorsque la température augmente mais diminue lorsqu’il y a davantage de proies extraguildes. Dans une dernière étude, nous soumettons le système biologique à des pics de température. Nos résultats démontrent que ces pics diminuent la fécondité des pucerons, l’accroissement de leurs populations, le poids des larves de coccinelles et le contrôle des pucerons par les coccinelles mais n’ont pas d’effets sur la plante et les relations plante-insecte. Le système biologique s’avère également plus résistant aux pics de température en présence de coccinelles qu’en leur absence. En conclusion, notre étude souligne l’importance de considérer la température dans les interactions trophiques puisqu’elle influence le comportement des organismes et la fréquence de leur interaction, ce qui se répercute au niveau des populations et des communautés. / There are several pieces of evidence that climate change significantly impact plants, herbivores, and predators. For ectotherms, temperature is the most important factor associated with these changes as it regulates their metabolism. Although the effects of temperature on individual organisms or populations have been well documented, our understanding about their consequences on trophic and guild interactions remains limited. In this context, we investigated the effects of temperature on complex interactions between a plant, the pepper Capsicum annuum L.; an herbivore, the aphid Myzus persicae Sulzer (extraguild prey); and two of its natural enemies, the ladybeetle Coleomegilla maculata lengi Timberlake (intraguild predator) and the predatory midge Aphidoletes aphidimyza Rondani (intraguild prey). We combined two approaches: (1) modeling predator–prey and intraguild (predation between two species that compete for the same resource) interactions, and (2) testing model predictions and characterizing the effects of temperature on components of our biological system through laboratory experiments. As predicted by the first model, we found that when temperature rises, C. maculata is more efficient at finding and handling prey, which increases predation rate. However, search rate decreases at high temperatures, leading to a reduction in predation. The predatory activity is therefore limited to a temperature window outside of which predation is reduced or absent. The next objective was to compare two models, one linear and one nonlinear, to determine which one best describes the functional response (the relationship between the number of prey consumed and prey density) of an intraguild predator. Results indicated that predictions of the nonlinear model (i.e., saturating at high prey densities) fit empirical observations well while the linear model greatly overestimates the number of prey consumed and the incidence of intraguild predation. Subsequently, we derived the nonlinear model to include the effect of temperature. As predicted by this model, we found that the incidence of intraguild predation increases with temperature but decreases when extraguild prey are more abundant. In a last experiment, we investigated the effects of temperature peaks on each component of our biological system. Results showed that temperature peaks reduce aphid fecundity and thereby population growth, decrease the weight of ladybeetle larvae, and decrease aphid control by ladybeetles, but have no effect on plants or plant–insect relationships. We also observed that the food chain is more resistant to temperature peaks when ladybeetles are included in the system than when they are absent. This suggests that ecosystems with predators exerting strong biotic control on prey population should be more resistant to climate change than ecosystem lacking them. In conclusion, our study highlights the importance of considering temperature in trophic and guild interactions since it influences the behavior of organisms as well as the frequency of interactions that affect population and community dynamics.
30

Bionomía, diversidad y morfología preimaginal de sírfidos depredadores (Diptera: Syrphidae) en el Estado Lara, Venezuela. Importancia en el control biológico de plagas

Arcaya, Evelin 23 October 2012 (has links)
Este estudio constituye una importante fuente de información sobre el potencial de los sírfidos depredadores (Diptera: Syrphidae, Syrphinae) como agentes biológicos para el control de plagas en cultivos agrícolas en Venezuela. Las larvas de los Syrphidae presentan una morfología muy variada y poseen una gran diversidad de modos de vida. La mayor parte de los representantes de la subfamilia Syrphinae, son depredadores de una amplia gama de hemípteros de cuerpo blando aunque también pueden alimentarse de otros artrópodos. Las principales presas de los sírfidos depredadores son los áfidos o pulgones (Aphididae), escamas (Coccoidea), aleuródidos (Aleyrodidae) y trips (Thripidae). Para la realización de la presente Tesis doctoral se realizó un muestreo en los principales cultivos del estado Lara y se revisó la colección del Museo de Entomología José M. Osorio (MJMO = UCOB, según el Biodiversity Collections Index) de la Universidad Centroccidental "Lisandro Alvarado". También se revisaron ejemplares de la colección del Museo del Instituto de Zoología Agrícola (MIZA) de la Universidad Central de Venezuela. Entre los resultados de la tesis, se presenta una base de datos con los sírfidos depredadores estudiados con un total de 2571 ejemplares agrupados en 11 géneros y 59 especies. Del total de especies estudiadas, al menos se identificaron 15 nuevos taxa para la ciencia. Adicionalmente, se realizó un inventario de las presas y plantas asociadas a cada especie de Syrphidae depredador. Se reportaron nuevas especies de presas y plantas asociadas que aumentan de manera significativa el conocimiento de estas relaciones conocidas hasta la fecha en Venezuela. Como ejemplo, para A. exotica, se indican 6 nuevas presas y 23 plantas hospedantes; para P. clavatus se registran 7 nuevas plantas hospedantes. Por último, destacar 26 nuevos registros de presas relacionadas con el género Ocyptamus sobre 33 especies de plantas asociadas, presentando la mayor diversidad de presas de todos los sírfidos estudiados. En función de los resultados obtenidos en el muestreo se procedió al estudio del potencial biológico de Allograpta exotica, Pseudodoros clavatus y Ocyptamus dimidiatus, utilizando como presa al áfido de las leguminosas, Aphis craccivora en condiciones de laboratorio. Los parámetros biológicos de la especie (A. exotica) fueron estudiados en detalle. Las curvas de respuesta funcional de A. exotica se ajustaron mejor y mostraron el valor más alto de R2 para el modelo Polinomial indicando una fuerte correlación entre el aumento de áfidos depredados por A. exotica y las diferentes densidades ofrecidas de A. craccivora. El coeficiente de determinación para el modelo de Holling sugiere que A. exotica responde al Tipo de curva II. De manera complementaria a los estudios anteriores, se procedió al análisis de la morfología preimaginal de los géneros Allograpta, Pseudodoros y Ocyptamus. Además, se estudió la morfología preimaginal de Eosalpingogaster umbra Mengual y Thompson, Salpingogaster nigra Schiner, Leucopodella sp. nov. y xanthandrus bucephalus (wiedemann) aportando las primeras informaciones conocidas sobre su morfología preimaginal y las implicaciones sistemáticas derivadas. Se describen por vez primera el pupario, la larva madura (L-3) y la quetotaxia de O. dimidiatus y O. gastrostactus. También se describen los puparios de Ocyptamus funebris, O. norina, O. phaeopterus O. stenogaster, Ocyptamus lividus, O. tristani y Ocyptamus sp.nov aff. attenuatus. Por último se incluye una clave de identificación diagnóstica de las especies de Ocyptamus cuya morfología preimaginal ha sido analizada en esta memoria. / Consejo de Desarrollo Científico, Humanístico y Tecnológico de la Universidad Centroccidental Lisandro Alvarado (CDCHT-UCLA), financiamiento al proyecto de Tesis Doctoral 003-DAG-2007.

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