Taxonomy and species-groups of the subgenus Crematogaster (Orthocrema) in the Malagasy region (Hymenoptera, Formicidae)

Abstract

The species-level taxonomy of the subgenus Crematogaster (Orthocrema) in the Malagasy region is evaluated with both morphological data from worker and queen ants, and genetic data from three nuclear markers (long wavelength rhodopsin, arginine kinase and carbamoylphosphate synthase). These two types of data support the existence of six Orthocrema species: Crematogaster madecassa Emery, C. rasoherinae Forel, C. telolafy sp. n., C. razana sp. n., C. volamena sp. n. and C. mpanjono sp. n. Two new synonyms of C. rasoherinae Forel are recognized, C. rasoherinae brunneola Emery, syn. n. and C. voeltzkowi Forel, syn. n., as these were not supported as distinct taxa by the data. A neotype is designated for C. rasoherinae; lectotypes are designated for C. madecassa, C. rasoherinae brunneola and C. voeltzkowi. Species descriptions, images, distribution maps and identification keys based on worker and queen ants are given for all six species. A diagnosis of the subgenus Orthocrema in the Malagasy region is presented for both workers and queens. Within the Malagasy Orthocrema, three distinct phylogenetic lineages are suggested by molecular and morphological data. Newly defined monophyletic species-groups are thus the C. madecassa-group (C. madecassa, C. telolafy and C. razana) and the C. volamena-group (C. volamena and C. mpanjono); C. rasoherinae represents an isolated lineage in the Malagasy region and its closest relatives remain unclear. Other interesting biological findings are the presence of an intermediate caste between workers and queens in C. rasoherinae and C. madecassa, and unusually large workers in C. volamena resembling a major caste. © Bonnie B. Blaimer.