The pseudo-radiate buttons: A taxonomic revision of the Cotula turbinata group (Asteraceae; Anthemideae) and the description of two new species

Cotula is a large genus of ca. 50 species, centred in the Cape Floristic Region of South Africa, but also extending into tropical Africa, Eurasia, Australia as well as the Americas. The urgent need for a taxonomic treatment of Cotula has long been acknowledged, with no formal revision available. To this end, a taxonomic revision of the Cotula turbinata group is presented here. Several of the species in this group have previously been treated under the segregate genus Cenia, which included both radiate and disciform species with apically swollen peduncles. The species within the C. turbinata group are however not truly radiate, but rather pseudo-radiate due to modified outer disc florets with a greatly enlarged dorsal lobe. These modified disc florets, or pseudo-rays, are unique to the C. turbinata group and to our knowledge within the tribe. At the beginning of this study three species were recognized, all occurring in the Greater Cape Floristic Region. Extensive herbarium and field studies have revealed the presence of an additional three species, two described here as new (Cotula calcicola Jakoet, Mucina & Magee and Cotula perennans Jakoet, Mucina & Magee) and a third re-instated from the synonymy, Cotula pruinosa (E.Mey. ex. DC.) Jakoet & Magee. As such we here recognize six species, distinguished by their life history, leaf dissection, floret lobe color and size, and cypsela morphology.