The Ant Genus Cardiocondyla (Hymenoptera: Formicidae): The Species Groups with Oriental and Australasian Origin

Abstract

The world-wide fauna of the genus Cardiocondyla is assessed to have 79 currently recognized species and is subdivided into 14 informal species groups plus three monotypical clades. It is argued that the phylogenetic placement of Cardiocondyla next to the genus Ocymyrmex Emery, 1886 as proposed by Blaimer et al. (2018) is doubtful. The main body of the paper is a species-level taxonomic revision of those six species groups and the one monotypical clade which have their centers of origin in the Oriental and Australasian regions. The fauna of this area comprises 26 species eleven of which are described as new: Cardiocondyla schulzi n.sp., C. argentea n.sp., C. semiargentea n.sp., C. argyrotricha n.sp., C. latifrons n.sp., C. micropila n.sp., C. allonivalis n.sp., C. excavata n.sp., C. goroka n.sp., C. subspina n.sp. and C. sulcata n.sp. Recognized as junior synonyms were: Cardiocondyla tsukuyomi Terayama, 1999 and C. breviscapus Seifert, 2003 of C. minutior Forel, 1899 and C. brevispinosa (Donisthorpe, 1948) of C. paradoxa Emery, 1897. Each confirmed species is characterized by verbal descriptions, 18 numerically recorded phenotypic characters, z-stack images in three viewing positions, the key, a differential diagnosis and, if available, a brief life history. Exploratory and hypothesis-driven data analyses of phenotypic characters support the separation of the cryptic species Cardiocondyla minutior Forel, 1899, C. goa Seifert, 2003 and C. tjibodana Karavajev, 1935, two of which have dispersed as tramp species to the New World. Missing development of postzygotic isolation due to very strong prezygotic barriers is indicated in the closely related species Cardiocondyla latifrons n.sp. and C. micropila n.sp. which produce fertile hybrids in laboratory rearings but apparently do not hybridize in a natural context even if nesting in close neighborhood. The strong prezygotic isolation is supposed to be generated by the prevalence of intranidal mating and the difficulty for a mated heterospecific gyne to become accepted in a foreign colony.