Hymenoptera. Chapter 12

Abstract

We present the fi rst review of Hymenoptera alien to Europe. Our study revealed
\nthat nearly 300 species of Hymenoptera belonging to 30 families have been
\nintroduced to Europe. In terms of alien species diversity within invertebrate
\norders, this result ranks Hymenoptera third following Coleoptera and Hemiptera.
\nTwo third of alien Hymenoptera are parasitoids or hyperparasitoids that were
\nmostly introduced for biological control purposes. Only 35 phytophagous species,
\n47 predator species and 3 species of pollinators have been introduced. Six
\nfamilies of wasps (Aphelinidae, Encyrtidae, Eulophidae, Braconidae, Torymidae,
\nPteromalidae) represent together with ants (Formicidae) about 80% of the alien
\nHymenoptera introduced to Europe. Th e three most diverse families are
\nAphelinidae (60 species representing 32% of the Aphelinid European fauna),
\nEncyrtidae (55) and Formicidae (42) while the Chalcidoidea together represents
\n2/3 of the total Hymenoptera species introduced to Europe. Th e fi rst two
\nfamilies are associated with mealybugs, a group that also included numerous
\naliens to Europe. In addition, they are numerous cases of Hymenoptera introduced
\nfrom one part of Europe to another, especially from continental Europe to
\nBritish Islands. Th ese introductions mostly concerned phytophagous or gall-
\nmaker species (76 %), less frequently parasitoids. Th e number of new records of
\nalien Hymenoptera per year has shown an exponential increase during the last 200
\nyears. Th e number of alien species introduced by year reached a maximum of 5
\nspecies per year between 1975 and 2000. North America provided the greatest part
\nof the hymenopteran species alien to Europe (96 species, 35.3%), followed by
\nAsia (84 species, 30.9%) and Africa (49 species, 18%). Th ree Mediterranean
\ncountries (only continental parts) hosted the largest number of alien
\nHymenoptera: Italy (144 spp.), France (111 spp.) and Spain (90 spp.) but no
\ncorrelation was found with the area of countries. Intentional introduction,
\nmostly for biological control, has been the main pathway of introduction for
\nHymenoptera. Consequently, the most invaded habitats are agricultural and
\nhorticultural as well as greenhouses. To the contrary, Hymenoptera alien in
\nEurope are mostly associated with woodland and forest habitats. Ecological and
\neconomic impacts of alien Hymenoptera have been poorly studied. Ants have
\nprobably displaced native species and this is also true for introduced
\nparasitoids that are suspected to displace native parasitoids by competition,
\nbut reliable examples are still scarce. Th e cost of these impacts has never
\nbeen estimated.