Abstract
We present the first review of Hymenoptera alien to Europe. Our study revealed that nearly 300 species of Hymenoptera belonging to 30 families have been introduced to Europe. In terms of alien species diversity within invertebrate orders, this result ranks Hymenoptera third following Coleoptera and Hemiptera. Two third of alien Hymenoptera are parasitoids or hyperparasitoids that were mostly introduced for biological control purposes. Only 35 phytophagous species, 47 predator species and 3 species of pollinators have been introduced. Six families of wasps (Aphelinidae, Encyrtidae, Eulophidae, Braconidae, Torymidae, Pteromalidae) represent together with ants (Formicidae) about 80% of the alien Hymenoptera introduced to Europe. The three most diverse families are Aphelinidae (60 species representing 32% of the Aphelinid European fauna), Encyrtidae (55) and Formicidae (42) while the Chalcidoidea together represents 2/3 of the total Hymenoptera species introduced to Europe. The first two families are associated with mealybugs, a group that also included numerous aliens to Europe. In addition, they are numerous cases of Hymenoptera introduced from one part of Europe to another, especially from continental Europe to British Islands. These introductions mostly concerned phytophagous or gall-maker species (76 %), less frequently parasitoids. The number of new records of alien Hymenoptera per year has shown an exponential increase during the last 200 years. The number of alien species introduced by year reached a maximum of 5 species per year between 1975 and 2000. North America provided the greatest part of the hymenopteran species alien to Europe (96 species, 35.3%), followed by Asia (84 species, 30.9%) and Africa (49 species, 18%). Three Mediterranean countries (only continental parts) hosted the largest number of alien Hymenoptera: Italy (144 spp.), France (111 spp.) and Spain (90 spp.) but no correlation was found with the area of countries. Intentional introduction, mostly for biological control, has been the main pathway of introduction for Hymenoptera. Consequently, the most invaded habitats are agricultural and horticultural as well as greenhouses. To the contrary, Hymenoptera alien in Europe are mostly associated with woodland and forest habitats. Ecological and economic impacts of alien Hymenoptera have been poorly studied. Ants have probably displaced native species and this is also true for introduced parasitoids that are suspected to displace native parasitoids by competition, but reliable examples are still scarce. The cost of these impacts has never been estimated.
Highlights
Hymenoptera is one of the four large insect orders exceeding 100 000 species in the world, the other major orders being Coleoptera, Lepidoptera and Diptera (Gauld and Bolton 1988, Goulet and Huber 1993)
We could ascertain a region of origin for 272 (95.1%) alien wasp species introduced to Europe
North America provided the greatest part of alien Hymenoptera occurring in Europe (96 species, 35.3%), followed by Asia (84, 30.9%) and Africa (49, 18%) (Figure 12.4)
Summary
Hymenoptera is one of the four large insect orders exceeding 100 000 species in the world, the other major orders being Coleoptera, Lepidoptera and Diptera (Gauld and Bolton 1988, Goulet and Huber 1993). A small family of chalcid wasps comprising about 80 species in Europe, including one alien species, introduced from North Africa to control fruit flies The hosts of these obligate parasitoids or hyperparasitoids are mostly Lepidoptera and Diptera, less frequently Coleoptera, Neuroptera or Hymenoptera (Delvare 1995, Delvare 2006). A large family of wasps represented by more than 700 species in Europe (Trjapitzin 1989), of which 55 are considered to be alien, introduced from different parts of the world for biological control of economically important pests (Noyes and Hayat 1994). A medium-sized family with about 300 species in Europe (Zerova 1978), of which seven are alien These alien species are not parasitoids but phytophagous and pests of crops or horticultural plants whilst most eurytomids are primarily ectoparasitoids or hyperparasitoids of extremely diverse groups of endophagous insects (Lotfalizadeh et al 2007). This trend is probably due to both the decreasing interest in research on biological control and to the growing concern over possible nontarget effects of biological control
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