Revision of the Australian ants of the genus Monomorium (Hymenoptera : Formicidae)

Abstract

The Australian ants of the genus Monomorium are revised. Fifty-nine species are recognised. Of these, 41 are described as new: Monomorium aithoderum, M. albipes, M. anderseni, M. anthracinum, M. arenarium, M. bifidum, M. bihamatum, M. brachythrix, M. burchera, M. capito, M. carinatum, M. castaneum, M. crinitum, M. decuria, M. disetigerum, M. draculai, M. durokoppinense, M. elegantulum, M. eremophilum, M. euryodon, M. flavonigrum, M. lacunosum, M. legulus, M. longinode, M. macarthuri, M. majeri, M. megalops, M. micula, M. nanum, M. nightcapense, M. nigriceps, M. parantarcticum, M. petiolatum, M. pubescens, M. ravenshoense, M. rufonigrum, M. shattucki, M. silaceum, M. stictonotum, M. striatifrons, and M. xantheklemma. Thirteen species pass into synonymy: M. armstrongi with M. whitei, M. broomense and M. ilia with M. laeve, M. donisthorpeiand M. fraterculus with M. fieldi, M. flavipes and M. insularis with M. leae, M. foreli with M. sordidum, M. howense with M. tambourinense, M. macareaveyi with M. bicorne, M. sanguinolentum with M. rubriceps, M. subapterum with M. rothsteini, and M. turneri withM. gilberti. Sixteen infraspecific forms are also synonymised: M. kilianii obscurelluminto M. kilianii, M. laeve nigriusand M. laeve fraterculus into M. fieldi, M. ilia lamingtonensisinto M. laeve, M. rothsteini humilior, M. rothsteini leda, M. rothsteini doddi and M. subapterum bogischi into M. rothsteini, M. rothsteini squamigena, M. rothsteini tostum and M. sordidum nigriventris into M. sordidum, M. fraterculus barretti and M. sydneyense nigella into M. sydneyense, M. gilberti mediorubra into M. gilberti, and M. rubriceps cinctumand M. rubriceps rubrum into M. rubriceps. Seventeen species and one subspecies are unchanged. Monomorium kiliani reverts to M. kilianii, M. kilianii tambourinenseis raised to species status, M. occidaneus is here treated as a species inquirenda, and M. flavigaster is removed from the genus Monomorium. Since the generic status of the latter taxon is uncertain, M. flavigaster is here regarded as incertae sedis. The supposedly extralimitalMonomorium talpa is synonymised under Monomorium australicum. At a higher taxonomic level the South American genus Antichthonidris is synonymised under Monomorium. Seven species-groups are proposed for the Australian fauna, (the bicorne-, falcatum-, insolescens-, kilianii-, longinode-, monomorium-, and rubriceps-groups). A cladistic analysis was undertaken of species for which all castes were examined (identifiable males and/or queens were lacking for all members of the falcatum-, insolescens- and longinode-groups). In all, fifteen species of Australian Monomorium were examined (M. bicorne, M. whitei, M. striatifrons and M. rufonigrum from the bicorne-group, M. crinitumand M. kilianii from the kilianii-group, M. fieldi, M. laeve, M. rothsteini, M. sordidum and M. sydneyense from the monomorium-group, and M. centrale, M. leae, M. euryodon and M. rubriceps from the rubriceps-group), together with Monomorium antarcticum(from New Zealand) and the Neotropical Antichthonidris denticulatus. The taxon used for the outgroup was the Neotropical ant Megalomyrmex modestus. Using the PAUP program, 37 characters for worker, queen and male castes were analysed. The clade incorporating the tiny generalists (M. fieldi, M. laeve, M. sordidum, and M. sydneyense), together with M. rothsteini, was found to be the clade most strongly supported as a monophyletic grouping. In this analysis M. euryodon was the sister taxon to the above clade. These ants were shown on this analysis to share a common ancestor with the other members of the rubriceps-group, with M. antarcticum and A. denticulatus, and with thekilianii-group. The relationships between these latter four sets of species were left unresolved, except that M. crinitum was shown to be the sister taxon to M. kilianii. The large, arid zone species in thebicorne-group were also shown as ancestral to the other Australian Monomorium. A key is provided to enable researchers to identify the workers of all Australian Monomorium, as well as extralimital species established in Australia.