Aphid parasitoids (Hymenoptera: Braconidae: Aphidiinae) in wetland habitats in western Palaearctic: key and associated aphid parasitoid guilds

This paper presents over 66 tritrophic parasitoid-aphid-plant associations from wetland habitats in western Palaearctic, comprising 24 parasitoid species, 24 aphid hosts and over 30 plant species, based on records from 25 countries. Seven new associations are documented. About half of the established tritrophic associations (34) were recorded rarely, while 6 associations have been documented more than 100 times each, based on 4 common and widespread Aphidiinae species. The majority of recorded parasitoid species (16) are involved in only 1-2 tritrophic associations, 7 species were recorded in 3-5 associations, and one species (Praon necans) is a member of even 16 different associations based on wetland habitats. Generally, the most frequently recorded associations are based on some very common and widespread parasitoids not specific for this class of habitats. On the basis of distribution, host range and habitat specialization we have divided aphid parasitoid associations in wetland habitats into three ecological categories. The most specialized group, containing rarely recorded parasitoid species whose distribution and aphid hosts are strictly associated with wetland habitats, is potentially highly vulnerable to extinction. The role of aphids associated with wetland habitats as reservoirs for economically important parasitoid species is discussed and a key for the identification of aphid parasitoids in wetland habitats is provided.