Molecular ecology, geography and species interactions of Mycopsylla insects with their bacterial endosymbionts, parasitoids and host fig trees

Abstract

Mycopsylla fici Tryon (Hemiptera: Homotomidae) is a plant sap-feeding pest insect that can cause complete defoliation of its sole host tree species, Ficus macrophylla Desf. ex. Pers., the Moreton Bay fig. It has been suggested that M. fici outbreaks happen during hot and dry years (Newman 2004). Its host has two forms; F. macrophylla f. macrophylla is present on the mainland of Australia and F. macrophylla f. columnaris on Lord Howe Island (LHI), a volcanic remnant located ~600 km off the coast of New South Wales. Since the 19th century, this fig species has also been planted outside its natural range within Australia (e.g. Melbourne, Perth) and overseas in New Zealand (e.g. Auckland), Europe and USA. In Australia only one other species of Mycopsylla has been described. Mycopsylla proxima Froggatt feeds on Ficus rubiginosa Desf. ex. Vent., but has not yet been reported to cause significant defoliation. Interestingly, while at least one parasitoid species has been observed attacking M. fici in Australia, no Mycopsylla specific parasitoid species has been formally described in M. fici natural range. One parasitoid species, Psyllaephagus cornwallensis, has been described in New Zealand, where M. fici is an alien species. This thesis presents multiple aspects of the intra- and inter-specific genetic relationships of Mycopsylla. By integrating multiple trophic levels involving Mycopsylla species, I present an excellent model system to study evolutionary questions on relationships between insect hosts, their parasitoids and endosymbionts. The incorporation of different spatial scales revealed and contrasted dispersal abilities of interacting species. This work contributes to the understanding of the interactions and dispersal of a poorly-known pest species, whose potentially drought-induced major outbreaks may become more common in our changing environment.

Date of Award	2017
Original language	English