Diet choice and habitat structure mediate coexistence of predatory mites on Jatropha curcas

• Ano de defesa: 2019
• Autor(a) principal: Marques, Renata Vieira Marques
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Universidade Federal de Viçosa
• Palavras-chave em Português: Ácaros - Controle biológico; Euseius concordis; Iphiseiodes zulluagai; Animais predadores; Dieta; Entomologia Agrícola
• Link de acesso: https://locus.ufv.br//handle/123456789/27290

Many animals select their diet based on the nutrient composition of their food, aiming to increase their performance. There are several studies showing that animals have a higher fitness when they feed on a mixed diet instead of feeding on single diets. Here, I studied two species of predatory mites, Iphiseiodes zuluagai and Euseius concordis, that showed a higher fitness when they fed on a diet composed of mixtures of the two natural prey species. Most importantly, these predators actively forage to obtain such a mixed diet. These two predators are being evaluated for their capacity to control the pest mites Polyphagotarsonemus latus and Tetranychus bastosi in plantations of the biodiesel plant Jatropha curcas. In the first chapter I assessed the performance of the predator E. concordis with a decreasing number of either of the two prey species to assess the optimal consumption of each prey. I found that the predator E. concordis selected a diet that maximized its reproduction. However, in nature, food items are usually patchily distributed, and with an increased distance between nutritionally complementary food types, the foraging animal needs to spend more energy and time to commute between different food sources. Thus, in the second chapter, I investigated whether the predator E. concordis does actively mix their diet when this requires foraging over longer distances than in the previous study, and I evaluated the effect on their fitness using their natural prey. Furthermore, the structure of the natural habitat of the prey is more complex than the structure offered in the experiments of Chapter 2. Thus, the foraging costs will also increase with increasing habitat complexity. In chapter 3, I therefore evaluated if the predator E. concordis mixed its diet when the two prey species occured spatially separated on a small J. curcas plant and if it benefitted from this. Although the predator had to spend time and energy to cover long distances to obtain a mixed diet, on small, intact plants, the predator actively foraged for a mixed diet, resulting in an increased oviposition. The structure of communities in nature as well as in biological control systems is not only affected by the interactions between plants and their pests, but also by interactions among their natural enemies. In theory, some interactions between the predators (such as intraguild predation) are predicted to disrupt pest control. Therefore, I investigated the possible interactions between the predatory mites E. concordis and I. zuluagai in Chapter 4. First, I show that the two predator species co-occur on the same J. curcas plants in the field. Second, I show that the two species are involved in reciprocal intraguild predation. Subsequently, I show that increasing the spatial structure and supplying alternative food resulted in increased coexistence of the two intraguild predators. In conclusion, these results suggest that to improve the persistence of predators in the field, it is important to increase the spatial structure of the habitat and offer a diverse predator diet.