Abstract
Dryocosmus kuriphilus (Hymenoptera: Cynipidae) is a global invasive gall wasp and a pest of chestnuts (Castanea spp.). A study of the Chalcidoidea parasitoid community of D. kuriphilus was undertaken over two years, from March 2017 to March 2019, at 15 sites in south and northwest Spain (Málaga and Galicia regions). More than 18,000 galls were collected, and 1153 parasitoids belonging to 22 species of seven chalcidoid families, plus two individuals of an inquiline Cynipidae, Synergus facialis, emerged. Richness was higher in the Málaga region, with 20 species, while 17 parasitoids and one inquiline were identified in Galicia. The parasitism rate of native chalcid parasitoid species in both regions was low. Eupelmus urozonus and Mesopolobus lichtensteini were the most abundant native species. Mesopolobus tibialis was a dominant species in south Spain, while Ormyrus pomaceus was a dominant species in northwest Spain. Our results revealed the existence of a sub-community of univoltine, probably host specialized, parasitoids in south Spain, which overwinter in galls, exhibiting a similar life cycle to Torymus sinensis. These species were Torymus notatus, Aulogymnus bicolor, Aulogymnus obscuripes and Aulogymnus balani. Data on the recovery of T. sinensis after release in the south Spain region show it to be well established, but its numbers are still low in northwest Spain.
Highlights
Non-native species are being introduced into many countries with increasing frequency
Mesopolobus tibialis was a dominant species in south Spain, while Ormyrus pomaceus was a dominant species in northwest Spain
Native parasitoid species recruited by D. kuriphilus on the Iberian Peninsula
Summary
Non-native species are being introduced into many countries with increasing frequency These exotic organisms can threaten and damage ecosystems, biodiversity, agriculture and even human health (Wittenberg and Cock, 2001; Pimentel et al, 2005; Pejchar and Mooney, 2009). Exotic species can disturb ecosystems and trophic networks through the displacement and extinction of native species (Gurevitch and Padilla, 2004), causing environmental damage and biodiversity loss (Vitousek et al, 1996; Pimentel et al, 2005). The damage to biodiversity and the economy produced by non-native species are due to their high propensity for dispersal and explosive production of large populations during the first years of an invasion resulting from their establishment in an environment without their natural enemies; the ‘enemy-release hypothesis’ (Williamson, 1996; Crawley, 1997). In the case of arthropodan biological invasions, one of the most important groups related to natural enemies is the parasitoids (Quicke, 1997; Schönrogge et al, 2006), mostly belonging to the order Hymenoptera that have theoretically co-speciated with their hosts through adaptations to overcome their hosts’ defences (top-down relations), and the hosts modifying their defences to avoid being parasitized (bottom-up relations) (Stone et al, 2002)
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