GEOGRAPHIC AND BETWEEN-GENERATION VARIATION IN THE PARASITOID COMMUNITIES ASSOCIATED WITH AN INVADING GALLWASP, ANDRICUS-QUERCUSCALICIS (HYMENOPTERA, CYNIPIDAE)

The knopper gallwasp Andricus quercuscalicis Burgsdorf 1783 (Hymenopte ra: Cynipidae) has invaded western and northern Europe from southern a nd eastern Europe over the last 400 years. A. quercuscalicis has two a lternating generations, which differ in phenology, structure, and host oak species. This study describes geographic variation in the communi ty in the tiny catkin galls of the sexual generation on Turkey oak, Qu ercus cerris, and compares the patterns obtained with those in the com munity attacking the alternate agamic generation. As predicted from co nsiderations of parasitoid recruitment to the communities of invading phytophagous insects (Cornell and Hawkins 1993), in its native range t he sexual generation shows (1) higher parasitoid community species ric hness, (2) higher total mortality due to parasitoid attack and (3) a h igher ratio of specialist to generalist parasitoid species than is evi dent in the invaded range. Counter to predictions, there is no indicat ion that parasitoid species than is evident in the invaded range. Coun ter to predictions, there is no indication that parasitoid community r ichness in the invaded range has increased with time since the arrival of the new host. Higher host mortality in the native range is due pri ncipally to a single specialist. Aulogymmus obscuripes Mayr 1877 (Hyme noptera:Eulophidae), and is not distributed evenly among parasitoid sp ecies which attack the gall-former only in this area. This contrasts w ith the community in Britain, where three principal generalist parasit oids cause approximately equal mortalities. The agamic gall contains a taxonomically and structurally diverse guild of parasitoid and inquil ine species, associated with the changing resource provided by a large , long-lived, complex gall. In contrast, the sexual community includes a taxonomically and structurally narrow guild, associated with a reso urce which is structurally simple, small in size and short-lived. No p arasitoid species attacks the gall-former in both generations. Surpris ingly, in spite of these differences in the nature of the gall resourc e in the two generations, over their entire range (native and invaded) the parasitoid guilds of the two are equally species rich.