Abstract
Since outbreaks of the invasive blue gum chalcids Leptocybe spp. began, the genus Megastigmus (Hymenoptera: Megastigmidae) has been increasingly studied as containing potential biocontrol agents against these pests. Megastigmus species have been collected and described from Australia, the presumed origin of Leptocybe spp., with M. zvimendeli and M. lawsoni reported as Leptocybe spp. parasitoids established outside of Australia. Parasitic Megastigmus have been reported to occur locally in the Neotropics, Afrotropic, Palearctic, and Indomalaya biogeographic realms, and in many cases described as new to science. However, molecular tools have not been used in studying parasitic Megastigmus, and difficulties in morphological taxonomy have compromised further understanding of eucalypt‐associated Megastigmus as well as the Megastigmus‐Leptocybe association. In this study, we used molecular markers to study the species composition and phylogeny of Megastigmus collected from eucalypt galls in Australia and from Leptocybe spp. galls from South Africa, Kenya, Israel, China, and Vietnam. We record thirteen discrete species and a species complex associated with eucalypt galls. A summary of morphological characters is provided to assist morphological delimitation of the studied group. A phylogeny based on 28S rDNA identified species groups of importance to Leptocybe spp. biocontrol agents from four clades with nine species. Relationships between Megastigmus from eucalypt galls and their phytophagous congeners were unresolved. Further molecular work is needed to clarify the identity of many species.
Highlights
Megastigmus, comprising 145 described species (Noyes, 2020), is the largest genus in the newly recognized family Megastigmidae (Janšta et al, 2018)
Six new Megastigmus species were described from Australia (Doğanlar, 2015; Doğanlar & Hassan, 2010), of which M. zvimendeli and M. lawsoni were released and established as biocontrol agents of L. invasa in Israel (Mendel et al, 2017)
Several species of Megastigmus have been recorded as associated with Leptocybe spp. in the Indomalaya, Palearctic, Afrotropic, and Neotropic biogeographic realms, and in many cases described as new species to science (Le et al, 2018)
Summary
Megastigmus, comprising 145 described species (Noyes, 2020), is the largest genus in the newly recognized family Megastigmidae (Janšta et al, 2018). Before 2000, literature of non-Australian Megastigmus predominantly described phytophagous species, while records from Australia largely comprised of entomophagous Megastigmus (Auger-Rozenberg et al, 2006; Grissell, 1999; Roques & Skrzypczyńska, 2003). Discrimination of Megastigmus associated with Leptocybe spp. has so far relied largely on morphology (Doğanlar, 2015; Doğanlar & Hassan, 2010). This has caused uncertainty and impeded further understanding of phylogenetic relatedness, since variation in color and sizes of specimens has long been known to challenge taxonomists, those working with Australian species (Bouček, 1988; Milliron, 1949). This study is the first to report a molecular sequence comparison of gall-associated Megastigmus in the eucalypt gall system
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
