Systematics and biogeography of Australian rhopalosomatid wasps (Hymenoptera: Rhopalosomatidae) with a global synopsis of the enigmatic genus Olixon Cameron

Abstract The wasp family Rhopalosomatidae is represented in Australia only by the genus Olixon Cameron. Species of this genus have previously been considered rare based on material in collections and have rarely been observed in the field. All known species of Olixon are brachypterous, solitary ectoparasitoids of crickets (Orthoptera: Gryllidae). Prior to our study the world fauna comprised 11 species of which two were endemic to north‐eastern Australia. Based on specimens collected during recent intensive surveys in Australia we record 17 species for the continent. Fifteen of these species are described as new, which more than doubles the world fauna of Olixon: Olixon abrahami, O. danggari, O. ferrugineum, O. guyim, O. harveyi, O. helgae, O. jandakotae, O. jawoyn, O. jenningsi, O. kakadui, O. pilbara, O. wajuk, O. waldockae, O. wuthathi and O. zonale spp.n . Females of Olixon australiae Perkins and Olixon flavibase Townes are redescribed, and the male of O. flavibase is described for the first time. A key is provided for all 17 Australian species and their distribution is discussed. Results of a cladistic analysis of the world species of Olixon based on 41 morphological characters for 24 ingroup species are presented. The results obtained from equal and implied weighting parsimony analyses indicate that: (i) the Australian species of Olixon are not monophyletic, (ii) about three‐quarters of the Australian species form a monophyletic group, and (iii) a Central/South American Olixon is sister to all other species. The implications of these results for the biogeography of world Olixon species are briefly discussed.