No abstract

The genus Megastigmus Dalman, 1820 (Hymenoptera: Megastigmidae) contains potential biocontrol agents of the invasive eucalypt galling chalcid Leptocybe spp. (Hymenoptera: Eulophidae), with several species reported in various parts of the world. Species discrimination is challenging due to intraspecific morphological variation, difficulty in measuring sizes of body parts, and the lack of information regarding the global distribution of parasitic Megastigmus. We used two species commonly associated with Leptocybe in its native range to review taxonomic methods and determine the most reliable morphological characters in species delimitation. We examined size variation of body characters, and conducted species discrimination using multivariate ratio analysis, mitochondrial Cytochrome c oxidase subunit 1 (COI) and nuclear 28S rDNA (28S) sequences. Morphological traits were effective in species delimitation yet revealed high variation in several characters employed in current keys. Knowledge generated on morphology and DNA justified the description of a new species, M. manonae, sp. n., the first record of M. pretorianensis in Australia, and revised diagnostic characters for M. zvimendeli. Based on these diagnostic characters and molecular data, we synonymize three species (M. judikingae, syn. n., from Australia, M. sichuanensis, syn. n., from China and M. icipeensis, syn. n., from Kenya) with M. zvimendeli. Our findings highlight the importance of molecular markers in assisting taxonomic decision-making and the need for coordinated work in identifying Megastigmus associated with Leptocybe spp.

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.

No abstract

No abstract