Dissertations / Theses on the topic 'Predatory arthropod'

Orientador: Gustavo Quevedo Romero
Texto em português e inglês
Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia
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Resumo: Com a intensificação das transformações dos sistemas naturais pela atividade humana, o entendimento dos processos que afetam as comunidades e o funcionamento dos ecossistemas tornou-se um tema central para a ecologia contemporânea. As interações entre as espécies, bem como as interações entre as espécies e os componentes abióticos do meio ambiente, afetam tanto os padões de diversidade biológica como funções ecossistêmicas. Neste trabalho, buscou-se compreender o papel relativo das interações predador-presa e dos componentes abióticos sobre as propriedades das comunidades e funcionamento dos ecossistemas. No primeiro capítulo, investiguei o papel do tamanho do habitat sobre os efeitos de predadores terrestres na estrutura de comunidades e funcionamento de ecossistemas adjacentes. O tamanho do habitat modera cascatas tróficas dentro de ecossistemas, deste modo, esperei que efeitos similares do tamanho do habitat poderiam afetar cascatas tróficas que ocorrem através dos limites dos ecossistemas. No segundo capítulo, explorei predições relacionadas a variação no formato de pirâmides tróficas de biomassa ao longo de gradientes ambientais (tamanho do habitat, concentração de detritos e produtividade). Além disso, investiguei a contribuição relativa dos efeitos de consumo direto e do risco de predação nas interações predador-presa como mecanismos estruturadores de pirâmides tróficas de biomassa. No terceiro capítulo, tive como objetivo investigar os efeitos de dois extremos de um gradiente ambiental e os efeitos de predadores sobre os componentes da diversidade de presas detritívoras (i.e., diversidade funcional, filogenética e taxonômica). Além disso, explorei o papel relativo do ambiente, dos predadores e dos componentes da diversidade sobre o funcionamento ecossistêmico (i.e., decomposição e fluxo de nitrogênio). Os resultados encontrados nos três capítulos demonstram que fatores abióticos são cruciais na determinação das propriedades das comunidades, interações predador-presa e, consequentemente, no funcionamento ecossistêmico. O papel relativo dos efeitos cascatas de predadores é altamente dependente das condições ambientais que medeiam as interações entre predadores e presas
Abstract: In the face of the increasing transformation of environmental conditions by human activity, understanding the processes that affect communities and ecosystem functioning has become fundamental goals in ecology. The interactions between coexisting species and, their interactions with the abiotic components of environment, affect the patterns of biological diversity and functions of ecosystems. In this study, I sought to understand the relative role of predator-prey interactions and of abiotic factors on the communities¿ properties and ecosystem functioning. In the first chapter, I investigated the role of habitat size in mediating the effects of terrestrial predators on the structure of communities and the functioning of adjacent ecosystems. Habitat size mediated trophic cascades within ecosystems; therefore, I expected that similar effects of habitat size affect cross-ecosystem trophic cascades. In the second chapter, I explored predictions related to the variation of trophic pyramids of biomass across environmental gradients (i.e., habitat size, detritus concentration and productivity). Furthermore, I investigated the relative contribution of consumptive and non-consumptive effects of predators on the shape of trophic pyramids of biomass. In the third chapter, I sought to investigate the effects of two extremes of an environmental gradient and the effects of predators on the components of detritivores diversity (i.e., functional, phylogenetic and taxonomic). Moreover, I explored the relative role of environment, predators and detritivore diversity components on the functioning of ecosystems (i.e., detritus processing and nitrogen flux). The results from this study demonstrated that abiotic factors are crucial determinants of community properties, predator-prey interactions and ecosystem functioning. The relative role of the predators cascading effects are strongly dependent on the environmental conditions which mediate the interactions between predators and prey
Doutorado
Ecologia
Doutora em Ecologia

The aphid Nasonovia ribisnigri (Hemiptera: Aphididae) and the thrips Frankliniella occidentalis (Thysanoptera: Thripidae) are two of the main pests in Mediterranean lettuce crops. The general goal of this Doctoral Thesis is to deepen in the study of the trophic interactions present in Mediterranean lettuce crops, in order to develop, apply and improve conservation biological control (CBC) programs using molecular techniques. Results showed the most abundant predator were Orius laevigatus, O. majusculus and O. niger (Hemiptera: Anthocoridae), the hoverflies Eupeodes corollae, Episyrphus balteatus and Sphaerophoria scripta/S. rueppellii (Diptera: Syrphidae), the coccinelid Coccinella septempunctata (Coleoptera : Coccidellidae) and spiders (Araneae: Linyphiidae, Thomosidae). Moreover, coccinellids were only found in spring, syrphids mainly in spring, but also in summer and Orius were only found in summer. With these abundances, the coccinellids were the most efficient predators of N. ribisnigri in spring; syrphids were the most efficient predators of F. occidentalis in spring; and Orius were the most efficient control agents of F. occidentalis in summer. In conclusion, molecular analysis of predation has allowed the characterization of the trophic links present in Mediterranean lettuce crops, which is of a great importance in order to develop CBC programs in those crops.
El pulgón Nasonovia ribisnigri ( Hemiptera: Aphididae ) y el trips Frankliniella occidentalis (Thysanoptera: Thripidae) son dos de las principales plagas en cultivos de lechuga mediterráneos. El objetivo general de esta Tesis Doctoral es profundizar en el estudio de las interacciones tróficas presentes en cultivos de lechuga mediterráneos, con el fin de desarrollar, aplicar y mejorar programas de control biológico (CB) por conservación mediante métodos moleculares. Los resultados mostraron que los depredador más abundantes fueron Orius laevigatus, O. majusculus y O. níger (Hemiptera: Anthocoridae ), los sírfidos Eupeodes corollae , Episyrphus balteatus y Sphaerophoria scripta / S. rueppellii (Diptera: Syrphidae), el coccinélido Coccinella septempunctata (Coleoptera : Coccidellidae) y arañas (Araneae: Linyphiidae, Thomosidae). Además los coccinélidos se encontraron sólo en primavera, los sírfidos principalmente en primavera, aunque también en verano y los Orius sólo en verano. Con estas abundancias, los coccinélidos fueron los depredadores más eficientes de N. ribisnigri en primavera; los sírfidos fueron los depredadores más eficientes de F. occidentalis en primavera; y Orius fueron los agentes de control más eficiente de F. occidentalis en verano. En resumen, los análisis moleculares de depredación han permitido la caracterización de las relaciones tróficas presentes en cultivos de lechuga del Mediterráneo, lo cual es de gran importancia para el desarrollo de programas de CB de este cultivo en esta zona.
El pugó Nasonovia ribisnigri (Hemiptera : Aphididae) i el trips Frankliniella occidentalis (Thysanoptera : Thripidae) són dues de les principals plagues en cultius d'enciam mediterranis . L'objectiu general d'aquesta Tesi Doctoral és aprofundir en l'estudi de les interaccions tròfiques presents en cultius d'enciam mediterranis , per tal de desenvolupar , aplicar i millorar programes de control biològic (CB) per conservació . Els resultats van mostrar que els tàxons de depredador més abundants van ser Orius laevigatus , O. majusculus i O. níger (Hemiptera : Anthocoridae), els sírfids Eupeodes corollae , Episyrphus balteatus i Sphaerophoria scripta / S. rueppellii (Diptera : Syrphidae), el coccinélid Coccinella septempunctata (Coleoptera : Coccidellidae) i aranyes (Araneae: Linyphiidae, Thomosidae). A més els coccinélidos es van trobar només a la primavera , els sírfids principalment a la primavera , encara que també a l'estiu i els Orius només a l'estiu . Amb aquestes abundàncies , els coccinélidos van ser els depredadors més eficients de N. ribisnigri a la primavera ; els sírfids van ser els depredadors més eficients de F. occidentalis a la primavera ; i Orius van ser els agents de control més eficient de F. occidentalis a l'estiu.En resum, les anàlisis moleculars de depredació han permès la caracterització de relacions tròfiques presents en cultius d'enciam de la Mediterrània la qual cosa és de gran importància per al desenvolupament de programes de CB d'aquest cultiu a la zona estudiada.

Predatory arthropods such as carabid beetles and spiders are generally thought to be favoured by crop management that results in dense vegetation. In grassland, silage production increases vegetarian density compared to grazed grass but involves disturbance from cutting, while intercropping with clover increases the vegetation density of vegetable crops, but causes yield loss through interspecific competition. The first part of this thesis compares the predatory arthropod fauna of silage with grazed grass. There were small differences between the carabid assemblages of the two habitats before the first silage cut, when the contrast between silage and grazed grass was greatest, and a general reduction in species richness following silage cutting. However, the responses of individual species varied greatly. Agonum muelleri and Calathus fuscipes were associated with grazing management, but no species were consistently favoured by silage production. For Loricera pilicornis, this may have been due to cool weather creating similar conditions in silage and grazed grass, while for Nebria brevicollis, which was susceptible to disturbance, the timing of cutting determined its distribution. Spiders showed a more uniform association with structurally complex vegetation and were thus generally found in higher numbers under silage management. The second part of the thesis investigates daily movements of predatory arthropods between dense vegetation, such as clover intercropped vegetables, and adjacent open, weeded crops. The results suggested that nocturnal carabids and spiders of the genus Erigone sheltered in dense vegetation by day and moved into the open at night. Thus intercropping only parts of a vegetable crop would enhance predatory arthropod activity throughout the crop, while reducing interspecific competition. These results showed that the relationship between increased vegetation density and predatory arthropod activity is less important in the habitats studied than other factors, such as disturbance and daily movements in determining the distribution of these animals.

Au cours des dernières décennies, d'énormes quantités de haies, de lisières ont été détruites en Europe tandis que le régime des incendies majeurs augmente dans les milieux méditerranéens. La perte de ces milieux de type lisières s'accompagne d'une chute catastrophique de la biodiversité. Notamment par la perte des refuges disponibles pour la faune. Cette thèse s'intéresse à l'importance des abris à différentes échelles et sur différents modèles biologiques. Premièrement, l'influence de la disponibilité en abris au pied des haies sur la biodiversité a été démontrée à l'aide d'inventaires et grâce à une expérimentation sur le terrain. Pour cela, une nouvelle approche d'inventaire qui combine les avantages des inventaires rapides et des techniques non létales a été mise au point. A une échelle intermédiaire, l'impact positif de l'ouverture du milieu forestier sur des populations de reptiles a été mis en évidence. Enfin, un suivi au niveau individuel de tortues d'Hermann a permis de suivre les conséquences de modifications l'habitat suite à un incendie majeur ; il suggère que les habitats brûlés restent favorables sur le long terme. En conclusion, l'importance des abris pour la biodiversité a été démontrée à plusieurs échelles d'espace, de temps et de précision. La conséquence pratique est que les fiches techniques de gestion des haies et des lisières devraient en tenir compte, ce qui n'est pas le cas actuellement.

Dans les agroécosystèmes, la biodiversité fonctionnelle et la biodiversité associée fournissent de nombreux services à l'homme dont la pollinisation, la régulation biologique et le cycle des nutriments. L'association des cultures est une pratique agricole qui augmente la diversité des plantes dans les agroécosystèmes, fournit des ressources alimentaires alternatives et structure les communautés des arthropodes. Elle favorise les prédateurs généralistes pour la régulation biologique des ravageurs. Cette étude vise à comprendre comment la diversité des plantes, à l'échelle de la parcelle, structure les réseaux trophiques des arthropodes et peut participer à améliorer la régulation biologique des ravageurs. Tout d'abord, une méta-analyse a été réalisée afin de rechercher la relation générale liant la diversité végétale considérée à l'échelle locale et le contrôle des insectes ravageurs par les prédateurs généralistes. Ensuite, sur un réseau de 20 parcelles paysannes de la région de Njombé au Cameroun, nous avons étudié l'effet de la diversité des plantes cultivées sur la structure du réseau trophique des arthropodes. Les résultats ont montré que l'abondance des prédateurs était positivement corrélée avec la diversité des plantes alors que celle des herbivores était négativement corrélée avec la diversité des plantes. L'effet inverse de la diversité des plantes sur les abondances des prédateurs et des herbivores suggère que des effets top-down structurent la communauté des arthropodes dans les parcelles de plantain. Enfin, l'effet de trois cultures couramment associées au plantain (maïs Zea mays, macabo Xanthosoma sagittifolium, et pistache Lagenaria siceraria) sur i) la structure de la communauté des fourmis et ii) les dégâts de Cosmopolites sordidus ont été étudiés dans un essai réalisé en station expérimentale. Les trois cultures associées ont eu un effet significatif sur l'abondance de tous les taxa de fourmis collectés mais le sens et la magnitude de cet effet ont varié selon les taxa. Cela montre le levier que constituent les cultures associées pour structurer la communauté des prédateurs généralistes de l'agroécosystème. Les abondances de tous les taxa de fourmis étaient également corrélées avec les dégâts de C. sordidus. Les abondances de Camponotus spp., Monomorium spp., Paratrechina longicornis et Tetramorium sp. étaient négativement corrélées avec les dégâts de C. sordidus montrant leur potentiel de régulation de ce ravageur. Cette étude à l'échelle de la communauté de l'agroécosystème suggère qu'il est nécessaire de prendre en compte les effets de la diversité végétale à tous les niveaux trophiques pour espérer maximiser le service de régulation des ravageurs.Mots clés : Diversité des plantes, cultures associées, réseaux trophiques, arthropodes, fourmis, structure de la communauté
Functional diversity and associated biodiversity in agroecosystems provide and promote important services to human society such as pollination, biological control, and nutrient cycling. Intercropping is a practical way to increase plant diversity in agroecosystems and participates to provide alternative foods and to structure arthropod communities, including generalist predators involved in pest control. To better understand how plant diversity structures the arthropod food web and how the control of pest may be optimized, we first made one meta-analysis to understand the mechanisms linking plant diversity to pest control by generalist predators at local scale. We second studied the effect of plant diversity on the arthropod community in contrasted plantain fields. We showed that predator abundance was positively correlated with plant diversity while herbivore abundance was negatively correlated with plant diversity. This strong and inverse effect of plant diversity on herbivore and predator abundance suggests that top-down forces structure the arthropod community in plantain fields and that it should be possible to structure the predator community to better control herbivores including pests. In a third step, we measured the effect of combinations of three associated crops maize Zea mays, cocoyam Xanthosoma sagittifolium and gourd Lagenaria siceraria as intercrops on ant community structure and then the effect relation between ant abundances with Cosmopolites sordidus damages. The three associated plants had a significant effect on abundance of all ant species but in different magnitudes and with either negative or positive effect showing that the selection of plant species that are intercropped is an efficient way to structure the ant community. The abundances of all species of ants were positively or negatively correlated with the damages of C. sordidus larvae. The abundances of Camponotus spp., Monomorium spp., Paratrechina longicornis and Tetramorium sp. were negatively correlated to C. sordidus damage. These ants appear to be the best candidates for C. sordidus control. These findings will help in the design of plantain agroecosystems that enhance pest control services.Keywords: Plant diversity, intercropping, arthropod food webs, ants, interspecific interactions, habitat structure

1. Plant quality (bottom-up effects) and natural enemies (top-down effects) affect herbivore performance. Furthermore, plant quality can also influence the impact of natural enemies. 2. Lower plant quality through reduced irrigation increased the abundance of the cryptic species from the Bemisia tabaci complex [hereafter B. tabaci Middle East Asia Minor 1 (MEAM1)], but not its natural enemies on cotton. It was therefore predicted that lower plant quality would diminish the impact of natural enemies in regulating this herbivore. 3. Over three cotton seasons, plant quality was manipulated via differential irrigation and natural enemy abundance with insecticides. Life tables were used to evaluate the impact of these factors on mortality of immature B. tabaci (MEAM1) over nine generations. 4. Mortality of B. tabaci (MEAM1) was consistently affected by natural enemies but not by plant quality. This pattern was driven by high levels of sucking predation, which was the primary (key) factor associated with changes in immature mortality across all irrigation and natural enemy treatments. Dislodgement (chewing predation and weather) and parasitism contributed as key factors in some cases. Analyses also showed that elimination of sucking predation and dislodgement would have the greatest effect on overall mortality. 5. The top-down effects of natural enemies had dominant effects on populations of B. tabaci (MEAM1) relative to the bottom-up effects of plant quality. Effects were primarily due to native generalist arthropod predators and not more host-specific aphelinid parasitoids. The findings of this study demonstrate the important role of arthropod predators in population suppression and validate the importance of conservation biological control in this system for effective pest control.

Davant les pèrdues de la producció agrícola global a causa de l'acció de les plagues, incrementades encara més per l'escalfament global, el control biològic per conservació (CBC) és una alternativa sostenible per mitigar aquestes pèrdues, en particular mitjançant poblacions naturals d'agents de control biològic (ACBs). L'estudi del paper que juguen els diferents hàbitats que componen el paisatge en el manteniment d'aquests ACBs en els cultius és necessari, i per a això també conèixer el moviment dels ACBs entre conreus i altres hàbitats del paisatge. L'objectiu general d'aquesta Tesi Doctoral és l'estudi del moviment d'artròpodes depredadors polífags entre elements del paisatge (cultius i àrees no conreades) a través de mètodes moleculars, per a una futura millora dels programes de CBC en els cultius d'alfals i préssec de la conca de l'Ebre. Per això, en primer lloc, es va dur a terme l'optimització d'una tècnica de marcatge tòpic amb un ADN no present en l'agroecosistema d'estudi (el crustaci Artemia spp.) i la seva amplificació per PCR convencional. Els resultats van demostrar el moviment des de l’alfals al préssec per part d'artròpodes depredadors d'interès pel control biològic (CB) de les plagues del préssec, com alguns coccinèl·lids, antocòrids del gènere Orius, mírids i crisopes (Capítol 1). Posteriorment, es va dur a terme la posta a punt d'un mètode d'anàlisi metagenòmic mitjançant un anàlisi multi-primer HTS (Capítol 2), per detectar els artròpodes i les plantes consumides pels principals artròpodes depredadors recol·lectats en dues parcel·les contigües de préssec i d’alfals a l'àrea d'estudi, amb la finalitat d'estudiar el seu moviment entre elements del paisatge. Per a això, es van determinar els paràmetres òptims per a la utilització d'aquesta metodologia de seqüenciació massiva mitjançant l'agrupació dels insectes en pools. També es va demostrar la necessitat de rentar els insectes més grans i amb major pilositat de manera prèvia a l'anàlisi metagenòmica, per la seva major capacitat de retenir el pol·len sobre la cutícula, i poder així detectar exclusivament el pol·len ingerit. En total, es van analitzar 13 taxons depredadors pertanyents a les famílies Cantharidae, Anthocoridae, Coccinellidae, MIridae i Lygaeidae, arribant a detectar 69 i 65 interaccions tròfiques artròpode-artròpode i artròpode-planta, respectivament (Capítols 2, 3 i 4). Aquestes van ser, des de relacions tròfiques ja conegudes sobre importants plagues d'alfals i préssec, com Aphis craccivora, Therioaphis trifolii, Liriomyza sp., Hypera sp. i Frankliniella occidentalis, que van confirmar el paper depredador d'espècies com Orius laevigatus, Orius niger, Nabis i Hippodamia variegata; fins interaccions tròfiques desconegudes fins al moment i d'importància per al control de plagues en préssec, com Grapholita molesta, Myzus persicae i Thrips fuscipennis, per part de Anthocoris nemoralis. Les plantes detectades, majoritàriament asteràcies, poàcies i solanàcies, van ser consumides per la majoria dels depredadors analitzats, posant així de manifestant la seva importància per a conservar els depredadors analitzats a prop dels cultius. Es va poder demostrar el moviment de depredadors des dels marges als cultius i entre cultius, ja fos a través de la detecció de preses, com Diaphorina lycii, insecte oligòfag de l'arbust Lycium europaeum, que va ser consumit per Anthocoris nemoralis i per Adelphocoris lineolatus; o mitjançant la ingestió directa de teixits vegetals, com Prunus persica consumit per Orius niger capturats en alfals. També es va detectar depredació intragremial entre el complexe de depredadors analitzats, així com amb altres enemics naturals presents en l'agroecosistema, com entre espècies del gènere Orius; o relacions depredador-parasitoide com Dinocampus coccinellae parasitant Coccinella septempunctata, o Leucostoma sp. parasitant Nabis sp. Aquesta metodologia ha permès també demostrar la omnivoria de la majoria espècies depredadores analitzades, fins i tot en aquells tàxons amb un conegut caràcter fitòfag, com Adelphocoris lineolatus, Nysius i Lygus. Fins i tot també detectar la ingestió per part d’Orius niger de tàxons d'insectes vectors de malalties que afecten el préssec, com la família Cicadellidae; o fins i tot de malalties que afecten animals, com la família Ceratopogonidae o Aedes caspius, suggerint un potencial efecte d'aquest depredador per minimitzar la transmissió d'aquestes malalties, a tenir en compte en un futur. Finalment, aquesta metodologia també ha permès detectar la presència d'espècies de difícil identificació morfològica com Nysius cymoides i Nysius graminicola. Nysius graminicola, plaga del préssec, va ser la presa consumida en un major nombre espècies depredadores. Tots aquests resultats han demostrat el gran potencial de la metodologia HTS utilitzada en aquesta Tesi Doctoral per a l'estudi de les interaccions tròfiques, així com del moviment en agroecosistemes d’insectes de diversa morfologia, informació necessària per posar a punt futurs programes de CB en préssec i en alfals.
Ante las pérdidas de la producción agrícola global debido a la acción de las plagas, incrementadas aún más por el calentamiento global, el control biológico por conservación (CBC) es una alternativa sostenible para mitigar estas pérdidas, en particular mediante poblaciones naturales de agentes de control biológico (ACBs). El estudio del papel que desempeñan los diferentes hábitats que componen el paisaje en el mantenimiento de estos ACB en los cultivos es necesario, y para ello también conocer el movimiento de los ACBs entre cultivos y otros hábitats del paisaje. El objetivo general de esta Tesis Doctoral es el estudio del movimiento de artrópodos depredadores polífagos entre elementos del paisaje (cultivos y áreas no cultivadas) a través de métodos moleculares, para una futura mejora de los programas de CBC en los cultivos de alfalfa y melocotón de la cuenca del Ebro. Para ello, en primer lugar, se llevó a cabo la optimización de una técnica de marcaje tópico con un ADN no presente en el agroecosistema de estudio (el crustáceo Artemia spp.) y su amplificación por PCR convencional. Los resultados demostraron el movimiento desde la alfalfa al melocotón por parte de artrópodos depredadores de interés para el control biológico (CB) de las plagas del melocotón, como algunos coccinélidos, antocóridos del género Orius, míridos y crisópidos (Capítulo 1). Posteriormente, se llevó a cabo la puesta a punto de un método de análisis metagenómico mediante un análisis multi-primer HTS (Capítulo 2), para detectar los artrópodos y las plantas consumidas por los principales artrópodos depredadores recolectados en dos parcelas contiguas de melocotón y de alfalfa en el área de estudio, con la finalidad de estudiar su movimiento entre elementos del paisaje. Para ello, se determinaron los parámetros óptimos para la utilización de esta metodología de secuenciación masiva mediante la agrupación de los insectos en pools. También se demostró la necesidad de lavar los insectos de mayor tamaño y con mayor pilosidad de manera previa al análisis metagenómico, debido a su mayor capacidad de retener el polen sobre la cutícula, y poder así detectar exclusivamente el polen ingerido. En total, se analizaron 13 taxones depredadores pertenecientes a las familias Cantharidae, Anthocoridae, Coccinellidae, Miridae y Lygaeidae, llegando a detectar 69 y 65 interacciones tróficas artrópodo-artrópodo y artrópodo-planta, respectivamente (Capítulos 2, 3 y 4). Estas fueron desde relaciones tróficas ya conocidas sobre importantes plagas de alfalfa y melocotón, como Aphis craccivora, Therioaphis trifolii, Liriomyza sp., Hypera sp. y Frankliniella occidentalis, que confirmaron el rol depredador de especies como Orius laevigatus, Orius niger, Nabis e Hippodamia variegata; hasta interacciones tróficas desconocidas hasta el momento y de importancia para el control de plagas en melocotón, como Grapholita molesta, Myzus persicae y Thrips fuscipennis, por parte de Anthocoris nemoralis. Las plantas detectadas, mayoritariamente asteráceas, poáceas y solanáceas, fueron consumidas por parte de la mayoría de los depredadores analizados, poniendo así de manifestando su importancia para conservar los depredadores analizados cerca de los cultivos. Se pudo demostrar el movimiento de depredadores desde los márgenes a los cultivos y entre cultivos, ya fuera a través de la detección de presas, como Diaphorina lycii, insecto oligófago del arbusto Lycium europaeum, que fue consumido por Anthocoris nemoralis y por Adelphocoris lineolatus; o a través de la ingestión directa de tejidos vegetales, como Prunus persica consumido por Orius niger capturados en alfalfa. También se detectó depredación intragremial entre el complejo de depredadores analizados, así como con otros enemigos naturales presentes en el agroecosistema, como entre especies del género Orius; o relaciones depredador-parasitoide como Dinocampus coccinellae parasitando Coccinella septempunctata, o Leucostoma sp. parasitando Nabis sp. Esta metodología ha permitido también demostrar la omnivoría de la mayoría especies depredadoras analizadas, incluso en aquellos taxones con un conocido carácter fitófago, como Adelphocoris lineolatus, Nysius y Lygus. Incluso también detectar la ingestión por parte de Orius niger de taxones de insectos vectores de enfermedades que afectan al melocotón, como la familia Cicadellidae; o incluso de enfermedades que afectan a animales, como la familia Ceratopogonidae o Aedes caspius, sugiriendo un potencial efecto de este depredador para minimizar la transmisión de estas enfermedades, a tener en cuenta en un futuro. Finalmente, esta metodología también ha permitido detectar la presencia de especies de difícil identificación morfológica como Nysius cymoides y Nysius graminícola. Nysius graminícola, plaga de melocotón, fue la presa consumida en un mayor número especies depredadoras. Todos estos resultados han demostrado el gran potencial de la metodología HTS utilizada en esta Tesis Doctoral para el estudio de las interacciones tróficas, así como del movimiento en agroecosistemas con insectos de diversa morfología, información necesaria para poner a punto futuros programas de CB en melocotón y en alfalfa.
Faced with global agricultural production losses due to pests' action, further increased by global warming, conservation biological control (CBC) is a sustainable alternative to mitigate these losses, mainly through natural populations of biological control agents (BCAs). The study of the role that the different habitats that compound the landscape play in the maintenance of the BCAs in crops is necessary, and for this reason, to know the movement of BCAs between crops and other habitats in the landscape is essential. The general objective of this Doctoral Thesis is to study the movement of polyphagous predatory arthropods among landscape elements (crops and non-cultivated areas) through molecular methods, for a future improvement of CBC programs in alfalfa and peach crops in the Ebro basin. To do this, firstly were performed the optimization of a topical marking technique with a DNA non present in the study agroecosystem (the crustacean Artemia spp.) and its amplification by conventional PCR. Results demonstrated the movement from alfalfa to peach by predatory arthropods of interest for the biological control (BC) of peach pests, such as some coccinellids, anthocorids of the genus Orius, mirids and chrysopids (Chapter 1). Subsequently, the development of a metagenomic analysis method was carried out through a multi-primer HTS approach (Chapter 2) to detect the main arthropod and plant consumed resources by the predatory arthropods collected in two contiguous plots of peach and alfalfa in the study area, in order to demonstrate its movement between elements of the landscape. To achieve this objective, the optimal parameters for using this massive sequencing methodology were determined by grouping insects by pools. The need to wash larger insects with greater hairiness before metagenomic analysis was also demonstrated, due to their remarkable ability to retain pollen on the cuticle, and thus be able to detect ingested pollen exclusively. In total, 13 predatory taxa belonging to the Cantharidae, Aanthocoridae, Coccinellidae, Miyridae and Lygaeidae families were analysed, detecting 69 and 65 arthropod-arthropod and arthropod-plant trophic interactions, respectively (Chapters 2, 3 and 4). These were trophic relationships already known on important pests of alfalfa and peach, such as Aphis craccivora, Therioaphis trifolii, Liriomyza sp., Hypera sp. and Frankliniella occidentalis, which confirmed the predatory role of species such as Orius laevigatus, Orius niger, Nabis and Hippodamia variegata; or other trophic interactions unknown until now on important pests in peaches, such as Grapholita molesta, Myzus persicae and Thrips fuscipennis consumed by Anthocoris nemoralis. The plants detected, mainly Asteraceae, Poaceae and Solanaceae, were consumed by most of the analysed predators, thus demonstrating their importance to conserve those predators near the crops. The movement of predators from the margins to the crops, and between crops, could be demonstrated, either through the detection of ingested prey, such as Diaphorina lycii, an oligophagous insect of the Lycium europaeum shrub, which was consumed by Anthocoris nemoralis and Adelphocoris lineolatus; or through the direct ingestion of plant tissues, such as Prunus persica consumed by Orius niger captured in alfalfa. Intra-guild predation was also detected among the complex of analysed predators and other natural enemies present in the agroecosystem, such as among species of the genus Orius; or predator-parasitoid relationships such as Dinocampus coccinellae parasitizing Coccinella septempunctata, or Leucostoma sp. parasitizing Nabis sp. This methodology has also made possible to demonstrate the omnivory of the majority of the predatory species analysed, even in those taxa with a known phytophagous character, such as Adelphocoris lineolatus, Nysius and Lygus. Even also allowed the detection of the ingestion by Orius niger of insect taxa vectors of diseases that affect peaches, such as the Cicadellidae family; or even diseases that affect animals, such as the family Ceratopogonidae or Aedes caspius, suggesting a potential effect of this predator to minimize the transmission of these diseases, to be considered in the future. Finally, this methodology has also made possible to detect species of difficult morphological identification such as Nysius cymoides and Nysius graminícola. Nysius graminícola, a peach pest, was the prey consumed in a higher number of predatory species. All these results have demonstrated the great potential of the HTS methodology used in this Doctoral Thesis to study trophic interactions and movement in agroecosystems with insects of diverse morphology, information necessary to fine-tune future CB programs in peach and in alfalfa.

Thesis (MSc)--Stellenbosch University, 2015.
ENGLISH ABSTRACT: Invasive arthropod predators are one of the largest and most diverse groups of invasive insects in the world. Many are generalist predators, with cosmopolitan distributions due to their use as biological control agents in agriculture. Harmonia axyridis (Coleoptera: Coccinellidae), an invasive arthropod predator species native to Asia, which now has a world-wide distribution. It is considered one of the most successful biological control predator species and is generally considered to be economically beneficial. However, negative effects have recently emerged in agricultural and natural systems. Harmonia axyridis poses a threat to biodiversity as it outcompetes native species for food resources. It can also feed directly on native predatory arthropods that disrupt natural ecosystem processes. Their movement in-and-out of agricultural landscapes may depend on food availability with natural vegetation alongside agricultural areas often utilised for refuge and alternative food resources. This beetle has also been recorded in urban areas. The aim of this study was to determine how the invasive H. axyridis beetle uses the local landscape in the Western Cape province, South Africa, and to determine its threat to native species. I sampled urban landscapes, vineyards, natural vegetation/vineyard edge zones and pristine natural areas for arthropods every second month using a suction sampler. Data collected included the abundance and diversity of H. axyridis, herbivores, local predators and non-Harmonia ladybeetles. Most H. axyridis were collected in urban areas during all sampling periods. Highest abundance was recorded in May and July (winter). This indicates that urban areas were the preferred landscape feature and that these act as ovipositing areas, particularly as larval H. axyridis were also only collected in urban areas. Significantly, vineyards and natural vegetation had very low abundance of H. axyridis, questioning their value as a biological control agent in this region. Harmonia axyridis had a negative effect on the overall local arthropod community, as well as the predator and herbivore guilds, although it was positively correlated with the abundance of non-Harmonia ladybeetles. This suggests that H. axyridis and non-Harmonia ladybeetles are responding to the same resources in these landscapes. A negative correlation found between H. axyridis and the abundance of predators is most likely due to competition for the same resources (e.g. prey items). These negative impacts, along with their negligible value as biological control agents in agriculture, suggest that a programme should be implemented to control this invasive species. More specifically, control should be aimed in urban areas during winter when and where the species aggregates and when larvae are present.
AFRIKAANSE OPSOMMING: Geleedpotige roofdiere is een van die grootste en mees diverse groepe van uitheemse insekte in die wêreld. Die meeste is veelsydige roofdiere, met wêreldwye verspreiding te danke aan hul gebruik as biologiese beheer agente in landbou gebiede. Byvoorbeeld, Harmonia axyridis (Coleoptera: Coccinellidae), 'n indringer geleedpotige roofdier spesies inheems aan Asië, het nou 'n wêreldwye verspreiding. Dit word beskou as die mees suksesvolle roofdier spesies wat gebruik word vir biologiese beheer en word oor die algemeen beskou as ekonomies voordelig. Negatiewe effekte was onlangs aangeteken beide in landbou gebiede en natuurlike areas. Harmonia axyridis hou 'n bedreiging in vir inheemse biodiversiteit as dit inheemse spesies uitkompeteer vir voedsel bronne. Dit kan ook direk voed op plaaslike roofsugtige geleedpotiges wat trofiese vlakke ontwrig en uiteindelik, biodiversiteit. Hulle beweging in-en-uit landbou landskappe kan gekoppel word aan die beskikbaarheid van voedsel, en gebruik natuurlike plantegroei langs landbou gebiede dikwels as 'n toevlugs oord en area vir alternatiewe voedsel bronne. Harmonia axyridis word ook in stedelike gebiede aangeteken. Die doel van hierdie studie was om te bepaal hoe die indringer Harlekynkewer die plaaslike landskap gebruik met die fokus op wingerde in die Wes-Kaap provinsie van Suid-Afrika, en tweedens om die bedreiging wat hierdie kewer moontlik vir inheemse spesies te bepaal. Ek het arthropoda in stedelike landskappe, wingerde, natuurlike plantegroei / wingerd rand sones en ongerepte natuurlike areas elke twee maande met behulp van 'n D-vac versamel. Monsters was ontleed deur gebruik te maak van die getalle van H. axyridis, herbivore, plaaslike roofdiere en nie-Harmonia liewenheers kewers. Die meeste H. axyridis was in stedelike gebiede versamel gedurende al die seisoene, maar meeste individue was gedurende Mei en Julie (winter) versamel. Hierdie toon dat stedelike gebiede die voorkeur-landskappe is vir hierdie kewers en dat hierdie gebiede opgetree as eierleggende gebiede, veral omdat larwes van H. axyridis slegs in hierdie gebiede aangeteken was. Wingerde en die natuurlike plantegroei het baie lae getalle H. axyridis gehuisves wat hul waarde as biobeheermiddel bevraagteken. Harmonia axyridis het 'n negatiewe uitwerking op die algehele plaaslike geleedpotige gemeenskappe gehad, asook op die die roofdier en herbivoor gildes, maar hul getalle was positief gekorreleer met die getalle van nie-Harmonia liewenheerskewers. Dit dui daarop dat H. axyridis en nie-Harmonia liewenheerskewers beide reageer op dieselfde hulpbronne in hierdie landskappe. 'n Negatiewe korrelasie was gevind tussen die getalle van H. axyridis en die getalle van ander predatoriese geleedpotiges at waarskynlik te danke was aan mededinging tussen hierdie groepe vir dieselfde hulpbronne (bv prooi). Hierdie negatiewe invloede, asook hul verminderde waarde as biobeheeragente in die landbou, dui daarop dat 'n program in werking gestel moet word om hierdie indringerspesies te beheer. Meer spesifiek, beheer moet gedurende die winter en in stedelike gebiede geskied, waar en wanneer hierdie spesie op sy volopste is en waar larwes teenwoordig is.

A l'aide d'essais de contamination menes dans les conditions controlees du laboraoire, le potentiel larvicide des hyphomycetes metarhizium anisopliae et tolypocladium cylindrosporum est eprouve sur le moustique aedes albopictus, un important vecteur de la dengue. Le role de l'age larvaire et de la mue comme facteurs de resistance aux infections est discute. Le spectre d'hote de la souche ma 139 est etudie sur les larves culiciphages du moustique toxorhyncites amboinensis. Des larves proies prealablement infectees par cette souche representent un inoculum potentiel pour ce predateur. Le mode d'action de ces germes est approfondi par des etudes histologiques et ultrastructurales qui ont notamment permis de suivre le comportement de leurs spores dans le mesenteron des larves et la penetration cuticulaire de t. Cylindrosporum. Le determinisme des processus toxemiques impliques dans la pathogenie de m. Anisopliae est precise par l'evaluation du nombre de spores ingerees par les larves

This study investigated the role that native insectary plants can play in promoting predatory arthropods, and thereby to enhance biological control of vineyard pests in Australia. I also set out to clarify if light brown apple moth (LBAM), Epiphyas postvittana (Walker) (Lepidoptera: Tortricidae) is the main lepidopteran pest of grapevines in vineyards. Economic damage is caused to grapevines each season by pest species and E. postvittana is considered the dominant insect pest in Australian vineyards. However, recent observations suggested that species of tortricids other than E. postvittana may also act as pests. I investigated which tortricids are present in local vineyards, and whether the diversity of tortricids varied significantly among vineyards. I used molecular methods to determine the species of tortricids present in the canopies of grapevines over two growing seasons. This study confirms that E. postvittana is the most common tortricid pest in South Australian vineyards. Acropolitis rudisana (Walker) (Lepidoptera: Tortricidae), lucerne leafroller, Merophyas divulsana (Walker) (Lepidoptera: Tortricidae), and cotton tipworm, Crocidosema plebejana (Zeller) (Lepidoptera: Tortricidae) are also present in grapevine canopies but have not been reported previously. I also sought to determine if three native candidate native insectary plants, Christmas bush, Bursaria spinosa (Cav.) (Apiales: Pittosporaceae), prickly tea-tree, Leptospermum continentale (Forst. and G.Forst) (Myrtales: Myrtaceae), and wallaby grasses, Rytidosperma ssp. (DC) (Poales: Poaceae) have the capacity to support populations of predatory arthropods throughout the year, and if they may also provide habitat for economically damaging vineyards pests. Surveys were conducted in Adelaide Hills, Barossa Valley and Eden Valley vineyards over a 12-month period. The data were analysed to answer the following questions. What is the biological and functional diversity associated with each plant species? What are the features of an effective, functional native insectary plant assemblage for use in and around vineyards? What is the level of similarity and dissimilarity between the arthropod faunas of each plant species? Each plant species was found to support diverse predator species, which should attack a range of other arthropod pests across their life stages. It may also be possible to increase the functional diversity of predatory arthropods by more than three times when B. spinosa or L. continentale is incorporated into a landscape containing vineyards. Rytidosperma ssp. provides valuable complementary habitat for predatory species other than those commonly found in association with the woody perennials. When Rytidosperma ssp. are included in a viii plant assemblage with each woody plant species, this could result in an average net increase in predator morphospecies richness of at least 27%. Species distribution modelling was used to examine the potential range of each plant species under different climatic conditions. The insectary plants are naturally adapted to all of the major wine growing regions within Australia. Vineyard managers are encouraged to explore the use of B. spinosa, L. continentale and Rytidosperma ssp. as insectary plants in their vineyards. This information could help wine grape growers to manage pests like LBAM, save time and money by producing grapes with lower pest incidence, while enhancing the biodiversity of their vineyards.
Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food & Wine, 2019

Thesis (Ph. D.)--University of Georgia, 2005.
Directed by John R. Ruberson. Includes articles submitted to Environmental entomology, Agriculture, ecosystems and environment, Entomologia experimentalis et applicata, Ecological entomology, and Oecologia. Includes bibliographical references.

Commercial sugarcane in South Africa is a monoculture, and therefore lacks vegetation diversity, which is instrumental in increasing associated faunal diversity. Diverse habitats tend to support more stable populations of herbivorous and predacious animals. It is hypothesised that lack of this diversity in sugarcane was partially responsible for the existence of Eldana saccharina infestation levels that are higher than is commercially acceptable. Amongst the available E. saccharina control strategies, is habitat management. This has been developed with the view of increasing and enhancing predator foraging activity. Through increasing arthropod predator abundance and activity, it is believed that E. saccharina control may be enhanced. In this study, habitat diversity was increased through intercropping beans within sugarcane. Arthropod populations were monitored throughout the sugarcane-growing period, to determine what effect this intercropping had on known potential arthropod predator populations of E. saccharina. The study site was divided into two plots: the intercrop (beans planted within sugarcane rows: sugarcane-bean intercrop) and sole sugarcane: control plot. At monthly intervals, epigeal arthropods were sampled with pitfall traps, while foliage associated arthropods were sampled with a suction trap. Predator activity at the base of the sugarcane stalk, where E. saccharina lays its eggs was monitored with sticky traps. Sampling took place in the sugarcane-bean intercrop and control plots as well as in the roadway bordering the study site. Epigeal predator habitat preference was assessed by randomly placing pitfall traps in the sugarcane rows, bean rows, interrows between sugarcane rows, interrows between sugarcane and bean rows and the roadway. Corresponding with monthly trapping, an E. saccharina infestation and damage survey was conducted. Environmental factors such as weather, light intensity, plant (beans and sugarcane) phenology and weed density were measured, and their effect on E. saccharina potential arthropod predators examined. At harvest, sugarcane stalks were sampled for sucrose yield analysis. Potential E. saccharina predators that were captured included species of the orders and/or families Acarina, Blattidae, Formicidae (Pheidole megacephala and Dorylus helvolus) and Araneida (Lycosidae, Oxyopidae, Thomisidae and Salticidae). P. megacephala and species of Acarina were the only predators caught with all three trapping techniques, thus indicating that they occurred both on the ground and foliage. D. helvolus and Acarina were the only predators caught in significantly higher numbers in the intercrop, suggesting that increased habitat management had positively affected their population sizes. D. helvolus were captured both on the ground and length of sugarcane stalk, while species of Acarina were captured on the ground, foliage and at the base of sugarcane stalk, indicating that they forage at the base of the stalk, where E. saccharina activity is concentrated. Specific ground habitats preferred by D. helvolus included the sugarcane rows and bean rows, while Acarina preferred the interrows between sugarcane and bean rows. Despite the generally low E. saccharina infestation levels during this study, significantly higher levels of infestation occurred in the intercrop when compared to sole sugarcane. As expected with high infestation, higher (although not statistically significant) damage occurred in the intercrop. Surprisingly, sucrose yield and sugarcane stalk mass were slightly higher in the intercrop. The implications of the observations made during this study are discussed in the context E. saccharina management.
Thesis (M.Sc.)-University of Durban-Westville, 1998.

Effects of prairie restoration on arthropod diversity was investigated at Gabis Arboretum, Valparaiso, Indiana. A total of 35,408 arthropods belonging to 13 taxa in the restored prairie (RP1 and RP2), old field (OF), and monoculture stand of Phalaris arundinacea (reed canary grass – RCG) sites, were captured, counted, and compared. The enhanced plant species diversity in the restored prairies did not appear to promote the diversity of arthropod taxa. However, the restoration led to a more balanced composition of arthropod functional groups and thus elevated the diversity of functional groups. The arthropod assemblages in the three sites diverged clearly according to my canonical correspondence analysis (CCA) ordination. Pollinator abundance was greatest at RP and least at RCG site, positively correlating with greater forb diversity, and suggesting greater potential for nectar feeding and pollination potential at RP sites. Herbivore abundance was greatest at the RP sites, positively correlating with increasing plant species diversity. Predator abundance was significantly greater at the RCG site compared to the OF and RP sites; it was positively correlated with greater C3 grass cover, a characteristic of the structurally homogenous RCG site, and negatively correlated with increasing plant diversity and forb cover, a characteristic of the diverse and more structurally complex RP sites. Given the apparent non-random distribution of arthropods among the field types, my results suggest plant species composition has a significant effect on arthropod assembly. The monoculture grass stand was found to have a predator dominated arthropod community supported by a small, diverse herbivore community. It is concluded that the prairie restoration has resulted in alteration of arthropod communities supporting greater pollinator and herbivore abundance and a more balanced ratio of herbivores to predators due, in part, to increased plant structural diversity.