THE PHYTOPHAGOUS INSECTS ON BUDDLEIA DAVIDII IN BRITAIN: A STUDY OF COLONISATION

Available from UMI in association with The British Library. Requires signed TDF.; Buddleia davidii is a recent Chinese introduction to Britain. It is not closely related to any other native British plant and current theories of colonisation suggest that it should have a depauperate phytophagous entomofauna. B. davidii has however acquired a sizeable phytophagous insect fauna, several species of which originally fed exclusively on the biennial Verbascum thapsus. This study therefore began by examining the phytophagous entomofauna of B. davidii and V. thapsus.; Polyphages dominated the Buddleia fauna with Verbascum and Urtica specialists forming the next most abundant groups. On Verbascum, polyphages and Verbascum specialists were equally abundant and Urtica specialists formed the next most abundant group. These results support the view that polyphages are highly predilected to colonise introduced plants and Verbascum and Urtica specialists are predilected to colonise Buddleia.; Several plant characters known to influence herbivory were examined for both B. davidii and V. thapsus. The most striking of these was the much thicker trichome layer on the Verbascum leaves compared with that on Buddleia.; Aphis verbasci (Homoptera:Aphididae) is one Verbascum specialist that has colonized B. davidii. Evidence from electrophoresis and discriminant analysis on biometric measurements suggest that it is the same population of aphids that colonises B. davidii and V. thapsus. The sexuales of this aphid were found on Buddleia and are described.; The lifetime performance (longevity, fecundity, adult weight) of A. verbasci was significantly better on 1st and 2nd year Verbascum than Buddleia, however mortality was so high on 1st year Verbascum that the "colony" performance was significantly better on Buddleia than 1st year Verbascum. It is argued that the dense trichome layer on 1st year Verbascum is the chief mortality factor. (Abstract shortened by UMI.)...