Orientador: Wesley Augusto Conde Godoy / Resumo: As interações interespecíficas em dípteros califorídeos de importância forense resultam de processos biológicos complexos, envolvendo comportamentos específicos capazes de influenciar tanto a abundância como a diversidade de insetos presentes nos substratos orgânicos em decomposição. Nesse sentido, a presença de determinadas espécies com forte ação interativa, como por exemplo, predadores, competidores ou parasitóides, pode interferir substancialmente na composição da fauna decompositora de cadáveres, com sérias implicações para a estimativa de intervalo pós-morte em investigações criminais. Em estudo prévio foi investigado em laboratório o comportamento de oviposição em L. eximia, C. megacephala e C. albiceps na tentativa de esclarecer se a postura de ovos em moscas-varejeiras ocorre meramente ao acaso, ou se a presença prévia de diferentes espécies pode influenciar a desova por parte das espécies que chegaram ao local subsequentemente. Os resultados encontrados indicam que as espécies L. eximia e C. megacephala escolhem sítios de oviposição em que não há a presença prévia de larvas de C. albiceps, uma espécie predadora intraguilda. Esses resultados sugerem estudos mais aprofundados, preferencialmente em populações naturais, focalizando sobre a interação entre larvas e adultos de moscas-varejeiras, já que há evidências de que fêmeas adultas são capazes de detectar a presença de larvas predadoras, o que influi na decisão oviposicional. Este estudo teve o objetivo geral de investigar a abundância, diversidade e dinâmica comportamental em populações de moscas-varejeiras no contexto de recursos alimentares efêmeros e limitados, considerando a ação da predação intraguilda. A proposta do estudo é criar duas frentes de investigação no contexto de ecologia comportamental, experimentação em campo e modelagem matemática populacional / Abstract: The interspecific interactions in calliphorid flies of forensic impoltance result of complex biological processes, involving specific behaviors capable of influencing both the abundance and the diversity of insects in organic substrates in decomposition. The presence of certain species with a strong interactive action, such as predators, competitors or parasitoids, can interfere substantially in the composition of the decomposer fauna of corpses, with serious implications for the postmortem interval estimate in criminal inquiries. In a previous study the oviposition behavior in L. eximia, C. megacephala and C. albiceps was investigated in laboratory in the attempt to clarify if the egg laying in blowflies occurs at random, or if the previous presence of different species may influence the oviposition of the species that had arrived subsequently at the substrate. The results suggest that the species L. eximia and C megacephala prefer oviposition substrates, without the previous presence of C. albiceps larvae, an intraguild predator species. These results suggest further studies, preferably in natural populations, focusing on the interaction between larvae and adult of blowflies, since there is evidence that females are able to detect the presence of predator. This study had the general objective of investigating the abundance, diversity and behavioral dynamic in populations of blowflies in the context of limited and ephemeral food resources, considering the effect of intraguild predation. The proposal of the study is to create two fronts of investigation in the context of behavioral ecology, experimentation in field and population mathematical modeling / Mestre

Dans ce travail de thèse, nous étudions des modèles mathématiques de la dynamique des populations en environnements déterministe et stochastique. Pour les environnements déterministes, nous considérons trois modèles. Le premier est un modèle intra-guilde prenant en compte des effets d'un environnement spatial hétérogène avec une migration rapide des individus entre les différents sites. Le deuxième est un modèle de pêche dans une zone constituée d’une aire marine protégée où la pêche est interdite et d’une zone où la population de poissons est pêchée. Enfin le troisième est un modèle prédateur-proie considérant une proie et deux prédateurs avec des réponses fonctionnelles de Beddington-DeAngelis. Pour les environnements stochastiques, nous étudions un modèle épidémique SIRS et un modèle prédateur-proie en prenant en compte un bruit télégraphique. Nous étudions le comportement dynamique de ces modèles et nous recherchons les conditions de maintien ou de disparition des espèces modélisées. / In this thesis, we consider mathematical population dynamics models in deterministic and stochastic environments. For deterministic environments, we study three models: an intraguild model with the effects of spatial heterogeneous environment and fast migration of individuals; a fishery model with Marine Protected Area where fishing is prohibited and an area where the fish population is harvested; a predator-prey model which has one prey and two predators with Beddington-DeAngelis functional responses. For stochastic environments, we study SIRS epidemic model and predator-prey models under telegraph noise. We try to present the dynamical behavior of these models and show out the existence or vanishing of species in the models.

Understanding how temperature affects biological systems is a central question in ecology and evolutionary biology. Anthropogenic climate change adds urgency to this topic, as the demise or success of species under climate change is expected to depend on how temperature affects important aspects of organismal performance, such as growth, development, survival and reproduction. Rates of biological processes generally increase with increasing temperature up to some maximal temperature. Variation in the slope of the initial, rising phase has attracted considerable interest and forms the focus of this thesis. I explore variation in growth rate-temperature relationships over several levels of biological organization, both between and within species, over individuals’ lifetime, depending on the ecological context and in relation to important life history characteristics such as generation length and winter dormancy.       Specifically, I examine how a clade of temperate damselflies have adapted to their thermal environment along a 3,600 km long latitudinal transect spanning from Southern Spain to Northern Sweden. For each of six species, I sampled populations from close to the northern and southern range margin, as well from the center of the latitudinal range. I reared larvae in the laboratory at several temperatures in order to measure indiviudal growth rates. Very few studies of thermal adaptation have employed such an extensive sampling approach, and my finding reveal variation in temperature responses at several levels of organization.       My main finding was that temperature responses became steeper with increasing latitude, both between species but also between latitudinal populations of the same species. Additional genetic studies revealed that this trend was maintained despite strong gene flow. I highlight the need to use more refined characterizations of latitudinal temperature clines in order to explain these findings. I also show that species differ in their ability to acclimate to novel conditions during ontogeny, and propose that this may reflect a cost-benefit trade-off driven by whether seasonal transitions occur rapidly or gradually during ontogeny.       I also carried out a microcosm experiment, where two of the six species were reared either separately or together, to determine the interacting effects of temperature and competition on larval growth rates and population size structure. The results revealed that the effects of competition can be strong enough to completely overcome the rate-depressing effects of low temperatures. I also found that competition had stronger effects on the amount of variation in growth rates than on the average value.       In summary, my thesis offers several novel insights into how temperature affects biological systems, from individuals to populations and across species’ ranges. I also show how it is possible to refine our hypotheses about thermal adaptation by considering the interacting effects of ecology, life history and environmental variation.

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.

<p>The abundance of predators and their impact on ecosystem dynamics is a vividly discussed topic in current ecology. In my studies, incorporating field observations, field experiments and theoretical modeling, I explored the importance of predators and predation in a low arctic tundra ecosystem in northern Norway. This involved observing the abundance and spatial activity of predators (raptors and small mustelids); manipulating the abundance of predators (spiders and birds) in an arthropod community; and exploring the theoretical consequences of intraguild predation on the coexistence among predators.</p><p>The results show that predation is important both in the arthropod assemblage and, depending on the productivity of the community, in the vertebrate assemblage. In arthropod communities predators are at least as abundant as their prey, whereas in the vertebrate part of ecosystem, predators are substantially less abundant than their prey. Still, in both cases predators had strong impact on their prey, influencing the abundance of prey and the species composition of prey assemblages. The impact of predation cascaded to the plant community both in the reticulate and complex arthropod food web and in the linear food chain-like vertebrate community. In the vertebrate-based community we could even observe the long time scale effect on plant community composition.</p><p>Within the predator community, exploitation competition and intraguild predation were the structuring forces. As the arthropod communities consist of predators with different sizes, intraguild predation is an energetically important interaction for top predators. As a consequence, they reduce the abundance of intermediate predators and the impact of intermediate predators on other prey groups. Moreover, being supported by intermediate predators, top predators can have stronger impact themselves on other prey groups.</p><p>In vertebrate communities, intraguild predation seems to be unimportant as energetic link, instead it manifests as an extreme version of interference competition. Therefore intraguild predation reduces the likelihood of coexistence, as it is due limited prey diversity and intense exploitative competition already precarious in the low arctic tundra.</p><p>In conclusion, predators have strong impact on their prey, especially in the more productive parts of the low arctic tundra. This applies even to the food webs with complex and reticulate structure, and these effects carry through the community both in the short time scale of population growth and on the long time scale of population generations.</p>

The abundance of predators and their impact on ecosystem dynamics is a vividly discussed topic in current ecology. In my studies, incorporating field observations, field experiments and theoretical modeling, I explored the importance of predators and predation in a low arctic tundra ecosystem in northern Norway. This involved observing the abundance and spatial activity of predators (raptors and small mustelids); manipulating the abundance of predators (spiders and birds) in an arthropod community; and exploring the theoretical consequences of intraguild predation on the coexistence among predators. The results show that predation is important both in the arthropod assemblage and, depending on the productivity of the community, in the vertebrate assemblage. In arthropod communities predators are at least as abundant as their prey, whereas in the vertebrate part of ecosystem, predators are substantially less abundant than their prey. Still, in both cases predators had strong impact on their prey, influencing the abundance of prey and the species composition of prey assemblages. The impact of predation cascaded to the plant community both in the reticulate and complex arthropod food web and in the linear food chain-like vertebrate community. In the vertebrate-based community we could even observe the long time scale effect on plant community composition. Within the predator community, exploitation competition and intraguild predation were the structuring forces. As the arthropod communities consist of predators with different sizes, intraguild predation is an energetically important interaction for top predators. As a consequence, they reduce the abundance of intermediate predators and the impact of intermediate predators on other prey groups. Moreover, being supported by intermediate predators, top predators can have stronger impact themselves on other prey groups. In vertebrate communities, intraguild predation seems to be unimportant as energetic link, instead it manifests as an extreme version of interference competition. Therefore intraguild predation reduces the likelihood of coexistence, as it is due limited prey diversity and intense exploitative competition already precarious in the low arctic tundra. In conclusion, predators have strong impact on their prey, especially in the more productive parts of the low arctic tundra. This applies even to the food webs with complex and reticulate structure, and these effects carry through the community both in the short time scale of population growth and on the long time scale of population generations.

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. / Doctorat réalisé en cotutelle entre l'Université de Montréal et l'Université Paul Sabatier-Toulouse III

Made available in DSpace on 2015-03-26T13:30:33Z (GMT). No. of bitstreams: 1 texto completo.pdf: 1105883 bytes, checksum: a8693b1ab79fc07546f743be5cf8c49a (MD5) Previous issue date: 2011-07-29 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Prey may be more or less consumed by control biologic agents and presents three kinds of interspecific interactions, (1) synergism, increase of mortality of prey comparing to each natural enemy independently, when the foraging of one species facilitates the capture of pest by another natural enemies. (2) Total mortality of the pest to natural enemies equals to the sum of individual mortality by each natural enemy. This occurs on independent natural enemies, when they prey different phases of pest&#8217;s life or in different temporal moments. (3) The total mortality of the pest by predator is lower than the individual sum for each predator. The decrease of predation tax may occur by different mechanisms, including the intraguild predation and the interespecific competition. Podisus nigrispinus (Dallas) and Supputius cincticeps (Stål) (Heteroptera: Pentatomidae), generalists predators of Neotropical region of South America, consume and share high variety of prey, not being restricted to inferior trophic level, because many may prey each other, on intraguild predation and on cannibalism. The aim of this work was determinate if there is competition and intraguild predation between P. nigrispinus and S. cincticeps. Besides that, study the effect of these phenomena on biology of the natural enemies and contribute to the understanding of interaction between predators on biologic control. On chapter I, the experiment was realized with adult females of this bugs and pupae of Tenebrio molitor Linnaeus (Coleoptera: Tenebrionidae) during nine days, when we analyzed the effect of intra and interespecific interactions on alimentary consume and on predation tax and the occurrence on cannibalism and intraguild predation among adults. On chapter II, we used second instar nymphs of the predators and pupae of T. molitor ad libitum were given once each four days. When they reach adult stage, couple were formed and we kept same treatment. The survival, cycle of life (second instar until hatch of adults), weigh, sexual ratio, longevity and reproductive aspects of bugs adults and intraguild predation and cannibalism between its nymphs were evaluated. Nymphs and adults of P. nigrispinusand S. cincticeps presented intraguild predation and cannibalism, which favors the survival of some nymphs until localization of the prey. On adult phase, bidirectional intraguild predation and the cannibalism were more frequently to S. cincticeps and increased the longevity of this species. The interespecific competition did not affect the alimentary consume, the predation tax, the development nor the reproduction of P.nigrispinus. The development and reproduction of S. cincticeps were affected, with the nymphal development shorter, production of bigger females and less viability of eggs, showing that this species is less competitive than P. nigrispinus. On higher prey density, these predators presented synergism on predation tax, which is good when it comes to biologic control. It is better to use only P. nigrispinus on inundative and inoculative biologic control, since this species presents higher predation and reproduction taxes. Besides that, the use of this predator with S. cincticeps may be unfavorable, because this is an intraguild predator and may lower P. nigrispinus population on lower prey availability or causes its migration. The low egg viability of S. cincticeps, bred with P. nigrispinus, is an indicative that is better to invest financial resources on P. nigrispinus production. However, in conservative biologic control, the use of both species is interesting because they can coexist at the same environment. Besides that, the egg viability of S. cincticeps presents constant decrease with interspecific interaction with P. nigrispinus, which may lead to a decrease of intraguild predation by this predator. / Presas podem ser mais ou menos consumidas por agentes de controle biológico e predadores apresentam três tipos de interações interespecíficas, (1) sinergismo, aumento da mortalidade da presa em relação a cada inimigo natural de forma independente, quando o comportamento de forrageamento de uma espécie facilita a captura da praga por outros inimigos naturais, (2) mortalidade total da praga por inimigos naturais em conjunto equivale à soma da mortalidade individual por cada um, ocorrem para inimigos naturais independentes, quando predam fases distintas da vida da praga ou em diferentes momentos temporais e (3) mortalidade total da praga por predadores em conjunto é menor que a soma da individual por predador. A diminuição na taxa de predação pode ocorrer devido à predação intraguilda e a competição interespecífica. Podisus nigrispinus (Dallas) e Supputius cincticeps (Stål) (Heteroptera: Pentatomidae), predadores generalistas da região Neotropical da América do Sul, consomem e compartilham alta variedade de presas, não sendo restritos ao nível trófico inferior, pois muitos podem se alimentar uns dos outros, na &#8220;predação intraguilda&#8221; e no canibalismo. O objetivo deste trabalho foi determinar se existe competição e predação intraguilda entre P. nigrispinus e S. cincticeps. Além disso, estudar o efeito desses fenômenos na biologia desses inimigos naturais e contribuir para a compreensão de interações entre predadores no controle biológico. No capítulo I, fêmeas adultas desses percevejos e pupas de Tenebrio molitor Linnaeus (Coleoptera: Tenebrionidae) foram mantidas durante nove dias para a análise das interações intra e interespecíficas no consumo alimentar e na taxa de predação e a ocorrência de canibalismo e predação intraguilda entre adultos. No capítulo II, ninfas de segundo estádio desses predadores foram alimentadas com pupas de T. molitor ad libitum e a cada quatro dias. No estágio adulto, casais foram formados e mantidos nos mesmos tratamentos. A sobrevivência, o ciclo de vida (segundo estádio à emergência dos adultos), peso, razão sexual, longevidade e aspectos reprodutivos dos adultos e a predação intraguilda e canibalismo entre suas ninfas foram avaliados. Ninfas e adultos de P. nigrispinus e S. cincticeps apresentaram predação intraguilda e canibalismo, que favorece a sobrevivência de algumas ninfas, até a localização da presa. Na fase adulta, a predação intraguilda e o canibalismo foram mais frequentes para S. cincticeps e aumentaram a longevidade dessa espécie. A competição interespecífica não afetou o consumo alimentar, a taxa de predação, o desenvolvimento e a reprodução de P. nigrispinus. O desenvolvimento e a reprodução de S. cincticeps foram afetados, com desenvolvimento ninfal mais curto, produção de fêmeas maiores e menor viabilidade de ovos, mostrando ser essa espécie menos competitiva que P. nigrispinus. Em alta densidade de presa, esses predadores apresentaram sinergismo na taxa de predação, o que é benéfico ao controle biológico. É melhor utilizar, apenas, P. nigrispinus nos programas de controle biológico inundativo e inocultaivo, pois essa espécie possui maior taxa de predação e reprodução. Além disso, o uso desse predador, com S. cincticeps, pode ser desfavorável, pois este é o predador intraguilda e pode diminuir a população de P. nigrispinus em baixadisponibilidade de presas, ou causar sua migração. A menor viabilidade de ovos de S. cincticeps, criado com P. nigrispinus, indica ser melhor investir os recursos financeiros na produção de P. nigrispinus. Porém, em programas de controle biológico conservativo, o uso de ambas as espécies é interessante por poderem coexistir no mesmo ambiente. Além disso, a viabilidade dos ovos de S. cincticeps apresenta queda constante com interação interespecífica com P. nigrispinus, o que dimuiria a predação intraguilda por esse predador.

Afin de limiter l’impact négatif des ravageurs sur les plantes cultivées, des agents de lutte biologique sont souvent introduits sous abris. Or, des interactions peuvent apparaître entre eux, comme la prédation intraguilde, et modifier l’efficacité de la lutte biologique. De plus, les défenses directes des plantes hôtes peuvent perturber l’efficacité des ennemis naturels. La question se pose donc de savoir s’il est possible de limiter les interactions négatives entre ennemis naturels et l’impact de la plante hôte sur leur développement. Pour répondre à cet objectif, afin d’optimiser la lutte biologique contre l’acarien Tetranychus urticae, ravageur très problématique, nous avons considéré deux cultivars de tomates caractérisés par des densités en trichomes et des concentrations en composés secondaires contrastéesl’acarien prédateur Phytoseiulus macropilis et Macrolophus pygmaeus, punaise prédatrice souvent employée pour lutter contre les aleurodes. Au cours d’essais conduits en serre, P. macropilis a permis de réguler T. urticae sans différence entre les deux cultivars, alors qu’en microcosmes le taux d’oviposition de P. macropilis a été supérieur sur le cultivar ayant la densité en trichomes non glandulaires la plus élevée. La consommation d’œufs de P. macropilis par M. pygmaeus en microcosmes n’a pas été observée en serre. Les interactions entre arthropodes se sont également traduites par une agrégation supérieure des T. urticae en présence des deux prédateurs et de P. macropilis en présence de M. pygmaeus. Avant de proposer P. macropilis comme nouvel agent de lutte bio / To suppress pest populations to such levels that damage to thecrop is minimized, multiple biological control agents are oftenintroduced in greenhouses. However, negative interactionsamong them, such as intraguild predation, might appear thatcan decrease the effi ciency of the plant protection strategy.Furthermore, plant direct (physical or chemical) defenseshave a negative impact on the pests but might also have animpact on the natural enemies. Therefore, the question iswhether it is possible to limit the negative interactions amongbiological control agents and the infl uence of the crop on thebehavior and development of the natural enemies. To optimizebiological control of Tetranychus urticae, a very problematicpest in tomato greenhouses, the effi ciency of the predatorymite Phytoseiulus macropilis was tested on two cultivars withdifferent trichome densities and concentrations of secondarycompounds, in presence or absence of Macrolophus pygmaeus,a mirid often used to regulate whitefl y populations.During two years, under greenhouse conditions, P. macropiliswell-controlled the population of T. urticae. There was no evidenceof intraguild predation between the two predators, butin the presence of M. pygmaeus, P. macropilis tended to havea more clumped spatial distribution. However, in microcosms,M. pygmaeus fed on P. macropilis eggs. Moreover, P. macropilislaid signifi cantly more eggs on the tomato cultivar with thehighest density of non-glandular trichomes, but this resultwas only observed in microcosms. The different dynami

Anthropogenic provisioning of water (water developments) to enhance abundance and distribution of wildlife is a common management practice in arid regions where water is limiting. Despite the long-term and widespread use of water developments, little is known about how they influence distribution, competition dynamics, and behavior of native species. To elucidate the potential influences of water developments on native species, we tested hypotheses concerning the occurrence and behavior of native kit foxes (Vulpes macrotis). First, we tested the indirect effect of water hypothesis (IEWH) which proposes that water developments negatively affect the arid-adapted kit fox by enabling a water-dependent competitor (i.e., coyote; Canis latrans) to expand distribution in arid landscapes. We tested the two predictions of the IEWH (i.e., coyotes will visit areas with water more frequently and kit foxes will avoid coyotes) and evaluated relative use of water by canids in the Great Basin and Mojave Deserts from 2010 to 2012. We established scent stations in areas with (wet) and without (dry) water and monitored visitation by canids to scent stations and water sources using infrared-triggered cameras. There was no difference in the proportions of visits to scent stations in wet or dry areas by coyotes or kit foxes at either study area. There was no correlation between visits to scent stations by coyotes and kit foxes. Visitation to water sources was not different for coyotes between study areas, but kit foxes visited water sources more in Mojave than Great Basin. The intense visitation to water by kit foxes in Mojave challenges our understanding that this species does not readily drink water. Our results did not support the IEWH in the Great Basin or Mojave Deserts for these two canids. Second, we tested three hypotheses that have been proposed to explain spatial variation in vigilance behavior. The predator-vigilance hypothesis (PVH) proposes that prey increase vigilance where there is evidence of predators. The visibility-vigilance hypothesis (VVH) suggests that prey increase vigilance where detection of predators is impeded or visibility is obstructed. The refuge-vigilance hypothesis (RVH) proposes that prey may perceive areas with low visibility (greater cover) as refuges and decrease vigilance. We evaluated support for these hypotheses using the kit fox, a solitary carnivore subject to intraguild predation, as a model. From 2010 to 2012, we used infrared-triggered cameras to record video of kit fox behavior at water developments in the Mojave Desert. The RVH explained more variation in vigilance behavior of kit foxes than the other two hypotheses (AICc model weight = 0.37). Kit foxes were less vigilant at water developments with low overhead cover (refuge) obstructing visibility. Based on our results, the PVH and VVH may not be applicable to all species of prey. Solitary prey, unlike gregarious prey, may use areas with concealing cover to maximize resource acquisition and minimize vigilance.