Invasive Leptocybe spp. and their natural enemies: global movement of an insect fauna on eucalypts.
The Eulophidae genus Leptocybe Fisher and La Salle and its type species L. invasa was first described in 2004 as an invasive galling pest causing serious damage to young eucalypts in the Middle East and Mediterranean. Believed to be of Australian origin, two cryptic species of Leptocybe have established throughout the world at an unprecedented rate. Australian parasitoids have been collected and released overseas for classical biocontrol of Leptocybe spp., some of which have also established via unassisted movement to other regions. Numerous other gall associates of Leptocybe spp. have been reported, both in Australia as the native range of eucalypts, and in countries where eucalypts are non-native. In this review, we describe the range expansion of Leptocybe spp. from its discovery to its current range of 43 countries, with reference to data supporting clarification of cryptic species. Records of Australian parasitoids of Leptocybe spp., through managed biocontrol programs and unassisted movement, are updated. Data detailing occurrences of potential parasitoids from nine families, of which the richest fauna are found in Australia and in southern Asia, are summarized. Emphasis is given to the Torymidae genus Megastigmus Dalman, which is distributed globally and associated with all current known invasive Leptocybe spp. Knowledge of the global movement of associates of Leptocybe spp. is expected to provide a model in understanding parasitoid - host and insect - host plant relationships. In addition, our summary of available data of potential parasitoids may assist policy makers and researchers in directing and prioritizing resources once alternative or additional biocontrol efforts are needed for management of Leptocybe spp.