Distribución y control de la especie invasora Dryocosmus kuriphilus Yasumatsu, plaga del castaño, en EspañaComunidades asociadas de parasitoides nativos, y control biológico y evaluación de impacto de la introducción en el medio natural de la especie foránea Torymus sinensis Kamijo

Abstract

Introduction”: The Asian chestnut gall wasp, Dryocosmus kuriphilus Yasumatsu, 1951 (Hymenoptera: Cynipidae) is a pest species of chestnut trees worldwide, acting as an invasive alien species and causing severe economic losses. This species causes fruit loss to these trees, shortened and deformed branches, as well as a generalised weakening, by inducing galls in high numbers. This galls production at high densities is because D. kuriphilus has no species that directly regulates its populations, unlike other native species of Cynipidae and parasitoid fauna of the superfamily Chalcidoidea (Hymenoptera). To regulate D. kuriphilus populations and prevent damage, the species Torymus sinensis Kamijo, 1982 (Hymenoptera: Chalcidoidea: Torymidae) has been used as a biological control agent and has been introduced into the wild in different countries around the world. The introduction of T. sinensis as a biological control of D. kuriphilus has proven to be effective in reducing populations of this pest species, but there are several unknowns about its interaction and negative effect on native species, both gallinducing cynipids and parasitoids. These negative effects include a) ‘non-target’ attack on native Cynipidae species, leading to population declines; b) competition with native parasitoid species leading to their displacement; and c) hybridization with other native Torymus species. Therefore, the release of T. sinensis presents a few uncertainties associated with species conservation problems in the natural environment. In addition, D. kuriphilus has generated new biological communities in chestnut trees, recruiting native parasitoid species present in oak trees. In Spain, the presence of D. kuriphilus and the release of T. sinensis are recent, and there are different knowledge deficits about the interaction of these two species together with native species, which generates a framework of study at the biological level of an environmental problem with strong socio-economic implications. “Aims”: This PhD thesis seeks to generate knowledge at different levels about the ‘D. kuriphilus-T. sinensis-native species’ trinomial, namely biogeography, ecology, and phylogeny. The aim of this knowledge is to help in the understanding and management of this pest and its biological control, as well as to indicate and prevent the possible damage that may be caused by the introduction of foreign species into the natural environment. “Synthesis”: At the biogeographical level, the distributions of D. kuriphilus and T. sinensis in Spain in the most current scenario have been established and detailed, including updates of new colonised areas, as well as the areas of maximum suitability for this pest species and possible future scenarios considering the natural dispersal of the species. In addition, the different natural introductions of T. sinensis across the French border and their different parasitism rates in different Iberian areas have been studied...