Publication: Cubiertas vegetales como estrategia para mejorar la biodiversidad de artrópodos y el control biológico en el cultivo del peral
Authors
Perera Fernández, Luis Gabriel
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Escuela Internacional de Doctorado
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Sánchez Sánchez, Juan Antonio
Publisher
Universidad de Murcia
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DOI
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info:eu-repo/semantics/doctoralThesis
Description
Abstract
El peral (Pyrus communis L.) es uno de los cultivos frutales de mayor relevancia en el sureste de la Península Ibérica. Entre sus principales amenazas destaca la psila del peral (Cacopsylla pyri L.; Hemiptera: Psyllidae), actualmente la plaga más importante en la región mediterránea. Las restricciones en el uso de insecticidas y la aparición de resistencias han incrementado el interés por estrategias alternativas, como el manejo de la cubierta vegetal del suelo para potenciar el control biológico por conservación. Sin embargo, el conocimiento sobre sus efectos en las comunidades de enemigos naturales y su contribución al control biológico es aún limitado.Esta Tesis Doctoral evaluó el efecto del manejo de la cubierta vegetal sobre la comunidad de artrópodos en huertos de peral en Jumilla (Murcia). Durante tres años se muestrearon parcelas con cubierta sembrada y parcelas con cubierta segada. Se analizó la comunidad de artrópodos del suelo y la comunidad de arañas tanto en la cubierta vegetal como en la copa de los árboles. Adicionalmente, se realizaron ensayos de laboratorio para estudiar las interacciones entre los principales enemigos naturales del sistema.El primer capítulo evaluó el efecto de la cubierta sembrada sobre la artropofauna del suelo. Los resultados mostraron que este manejo incrementó significativamente la riqueza y abundancia de artrópodos respecto a la cubierta segada. Se observó un aumento de enemigos naturales como arañas y coleópteros depredadores, mientras que algunos grupos detritívoros, como los colémbolos, redujeron su presencia. En el caso de las hormigas no se detectaron diferencias de abundancia a nivel del suelo entre los diferentes manejos de la cubierta.El segundo capítulo analizó la comunidad de arañas en la cubierta vegetal y en la copa del árbol. La cubierta sembrada favoreció significativamente la riqueza y abundancia de arañas en la vegetación del suelo, aumentando todas las familias su abundancia. En la copa de los perales también se observó una mayor presencia de arañas bajo cubierta sembrada, aunque solo las familias Linyphiidae, Theridiidae y Philodromidae tuvieron incrementos significativos. Estas familias presentaron una fuerte correlación entre sus abundancias en la cubierta y en el dosel, lo que sugiere un desplazamiento de individuos desde la cubierta hacia la copa.El tercer capítulo evaluó las relaciones intragremiales entre los principales depredadores del cultivo mediante ensayos de laboratorio. La hormiga Lasius grandis Forel (Hymenoptera: Formicidae) ejerció un efecto negativo sobre otros enemigos naturales, como el mírido depredador Pilophorus gallicus Ramane (Heteroptera: Miridae) y las arañas Philodromus lividus Simon (Araneae: Philodromidae) y Oxyopes lineatus Latreille (Araneae: Oxyopidae), confirmándose como depredador dominante en huertos mediterráneos. El impacto sobre las arañas estuvo condicionado por su comportamiento: O. lineatus, especie más activa, fue la más afectada, probablemente por una mayor probabilidad de encuentro con las hormigas. El mírido P. gallicus sufrió depredación tanto por hormigas como por arañas; sin embargo, su supervivencia aumentó cuando coexistía simultáneamente con hormigas y P. lividus, lo que sugiere modificaciones comportamentales bajo una presión combinada de estos depredadores.En conjunto, esta tesis demuestra que la implantación de cubiertas vegetales sembradas incrementa la diversidad y abundancia de enemigos naturales, especialmente depredadores generalistas como las arañas. No obstante, la eficacia potencial de esta estrategia no depende únicamente del aumento global de enemigos naturales, sino también de la composición de la comunidad y de las interacciones intragremiales entre depredadores. En este sentido, los resultados obtenidos indican que el manejo de cubiertas vegetales con fines de control de plagas debe considerar no solo el incremento de la biodiversidad, sino también el papel funcional de los distintos grupos de depredadores y sus interacciones, con el fin de maximizar su contribución efectiva al control biológico.
Pear (Pyrus communis L.) is one of the most important fruit crops in the south-east of the Iberian Peninsula. Among the main threats affecting this crop, the pear psyllid (Cacopsylla pyri L.; Hemiptera: Psyllidae) is currently the key pest in Mediterranean pear orchards. Restrictions on insecticide use and the development of resistance have increased interest in alternative strategies, particularly ground cover management as a tool for conservation biological control. However, knowledge about the effects of these practices on natural enemy communities and their contribution to biological control remains limited. This PhD thesis evaluated the effect of ground cover management on arthropod communities in pear orchards in Jumilla (Murcia, south-eastern Spain). Over a three-year period, plots with sown cover and plots with mown cover were sampled. Soil arthropod communities were analysed, as well as spider assemblages in both the ground cover vegetation and the tree canopy. In addition, laboratory experiments were conducted to study interactions among the main natural enemies present in the system. The first chapter assessed the effect of sown cover on soil arthropod fauna. Sown cover significantly increased soil arthropod richness and abundance compared with mown cover. Sown cover favoured natural enemies such as spiders and predatory beetles, whereas some detritivorous groups, including collembolans, decreased under this management. In contrast, ant abundance did not differ at ground level between cover management treatments. The second chapter examined spider communities in both the ground vegetation and the tree canopy. In the vegetation cover, the sown cover significantly increased spider richness and abundance, with all recorded families showing higher abundances. In the tree canopy, sown cover also promoted greater spider presence, although significant increases were restricted to a few families: Linyphiidae, Theridiidae and Philodromidae. These families also showed strong positive correlations between their abundances in the ground cover and in the canopy, suggesting movement of individuals from the cover vegetation to the tree canopy. The third chapter evaluated intraguild interactions among the main predatory arthropods through laboratory assays. The ant Lasius grandis Forel (Hymenoptera: Formicidae) exerted a negative effect on other natural enemies, including the predatory mirid Pilophorus gallicus Rambur (Heteroptera: Miridae) and the spiders Philodromus lividus Simon (Araneae: Philodromidae) and Oxyopes lineatus Latreille (Araneae: Oxyopidae), confirming its role as the dominant predator in Mediterranean pear orchards. The negative impact of the ant was mediated by spider behaviour, with O. lineatus, a more active species, being the most affected, probably due to a higher probability of encounters with ants. The mirid P. gallicus suffered predation from both ants and spiders. Notably, its survival increased when it coexisted simultaneously with ants and the spider P. lividus, suggesting possible behavioural changes in the mirid under combined predation pressure from these predators. Overall, this PhD thesis demonstrates that the establishment of a sown cover in pear orchards increases the diversity and abundance of natural enemies, particularly generalist predators such as spiders. Although these results support the potential of sown cover to enhance biological control, they also show that their effectiveness does not depend solely on increasing overall natural enemy abundance, but on the composition of the predator community and the intraguild interactions among its members. Therefore, ground cover management aimed at pest control should consider not only biodiversity enhancement, but also the functional role of different predator groups and their interactions, in order to maximise their effective contribution to biological control.
Pear (Pyrus communis L.) is one of the most important fruit crops in the south-east of the Iberian Peninsula. Among the main threats affecting this crop, the pear psyllid (Cacopsylla pyri L.; Hemiptera: Psyllidae) is currently the key pest in Mediterranean pear orchards. Restrictions on insecticide use and the development of resistance have increased interest in alternative strategies, particularly ground cover management as a tool for conservation biological control. However, knowledge about the effects of these practices on natural enemy communities and their contribution to biological control remains limited. This PhD thesis evaluated the effect of ground cover management on arthropod communities in pear orchards in Jumilla (Murcia, south-eastern Spain). Over a three-year period, plots with sown cover and plots with mown cover were sampled. Soil arthropod communities were analysed, as well as spider assemblages in both the ground cover vegetation and the tree canopy. In addition, laboratory experiments were conducted to study interactions among the main natural enemies present in the system. The first chapter assessed the effect of sown cover on soil arthropod fauna. Sown cover significantly increased soil arthropod richness and abundance compared with mown cover. Sown cover favoured natural enemies such as spiders and predatory beetles, whereas some detritivorous groups, including collembolans, decreased under this management. In contrast, ant abundance did not differ at ground level between cover management treatments. The second chapter examined spider communities in both the ground vegetation and the tree canopy. In the vegetation cover, the sown cover significantly increased spider richness and abundance, with all recorded families showing higher abundances. In the tree canopy, sown cover also promoted greater spider presence, although significant increases were restricted to a few families: Linyphiidae, Theridiidae and Philodromidae. These families also showed strong positive correlations between their abundances in the ground cover and in the canopy, suggesting movement of individuals from the cover vegetation to the tree canopy. The third chapter evaluated intraguild interactions among the main predatory arthropods through laboratory assays. The ant Lasius grandis Forel (Hymenoptera: Formicidae) exerted a negative effect on other natural enemies, including the predatory mirid Pilophorus gallicus Rambur (Heteroptera: Miridae) and the spiders Philodromus lividus Simon (Araneae: Philodromidae) and Oxyopes lineatus Latreille (Araneae: Oxyopidae), confirming its role as the dominant predator in Mediterranean pear orchards. The negative impact of the ant was mediated by spider behaviour, with O. lineatus, a more active species, being the most affected, probably due to a higher probability of encounters with ants. The mirid P. gallicus suffered predation from both ants and spiders. Notably, its survival increased when it coexisted simultaneously with ants and the spider P. lividus, suggesting possible behavioural changes in the mirid under combined predation pressure from these predators. Overall, this PhD thesis demonstrates that the establishment of a sown cover in pear orchards increases the diversity and abundance of natural enemies, particularly generalist predators such as spiders. Although these results support the potential of sown cover to enhance biological control, they also show that their effectiveness does not depend solely on increasing overall natural enemy abundance, but on the composition of the predator community and the intraguild interactions among its members. Therefore, ground cover management aimed at pest control should consider not only biodiversity enhancement, but also the functional role of different predator groups and their interactions, in order to maximise their effective contribution to biological control.
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