Physiological host range of two highly specialised mutualistic symbiotes: the fly Fergusonina turneri and its obligate nematode Fergusobia quinquenerviae,potential biocontrol agents of Melaleuca quinquenervia

In Australia, galls develop on Melaleuca quinquenervia (Cav.) S.T. Blake (Myrtaceae) as a result of the mutualistic association between the fly Fergusonina turneri Taylor (Diptera: Fergusoninidae) and its obligate nematode Fergusobia quinquenerviae Davies & Giblin-Davis (Tylenchida: Sphaerulariidae). The nematode induces gall formation, whereas the fly promotes gall maturation. Together they exploit M. quinquenervia buds and may inhibit stem elongation and flower formation. We delimited the physiological host range of this pair to determine their suitability as biological control agents of invasive M. quinquenervia populations in Florida, USA. Host use was assessed for eight species of Myrtaceae native to Florida, eight phylogenetically related ornamental species and oviposition alone on five non-myrtaceous species. Although oviposition was less specific, galls developed and matured only on M. quinquenervia. After establishment, galls are predicted to prevent flower and seed production, thereby reducing the regenerative potential of M. quinquenervia. This is the first example of an insect/nematode mutualism released as biological control agents of an invasive plant.