Unrecognised ant megadiversity in the Australian monsoonal tropics: The <i>Melophorus dicyrtos</i> Heterick, Castalanelli and Shattuck complex

Abstract It is becoming increasingly clear that the Australian monsoonal (seasonal) tropics is a global centre of ant diversity despite only a small proportion of species being described. Several monsoonal ‘species’ have recently been shown to be species groups or complexes containing dozens or even hundreds of species. Here we investigate species richness in samples attributable to Melophorus dicyrtos Heterick, Castalanelli and Shattuck, a recently described taxon occurring throughout monsoonal Australia. We obtained CO1 sequences from 74 specimens, and through integration of CO1 data with morphological variation and distributional information, we recognise 26 species from them. Images of all these are provided. All 26 putative species are supported by both Poisson tree processes (PTP) and Bayesian implementation of the PTP model analyses of CO1 divergence and clustering. Based on sample coverage and patterns of species turnover, we estimate that the total size of the M . dicyrtos complex is more than 50 species. Monsoonal Australia is not formally recognised as a region of high ant diversity, but this is an artefact of its hyperdiverse undescribed diversity. Our findings provide further evidence that monsoonal Australia harbours several thousand ant species, dwarfing that currently estimated for the Amazon basin where ant diversity is traditionally considered to be greatest.