CYANIXIA, A NEW GENUS FOR THE SOCOTRAN ENDEMIC BABIANA SOCOTRANA (IRIDACEAE–CROCOIDEAE)

Abstract

The sub-Saharan and mainly western southern African genus Babiana (Iridaceae–Crocoideae) is morphologically diverse, containing some 80 species. The Socotran B. socotrana, which differs from all other members of the genus inter alia in its trisulcate pollen grains, basic chromosome number, x=10, corms of axillary origin, and globose, colliculate–tuberculate seeds, is here excluded from Babiana and referred to the new genus Cyanixia. Other Babiana species have monosulcate pollen grains with a two-banded operculum, a basic chromosome number of x=7, terminal corm ontogeny, and derived pear-shaped seeds with a smooth glossy surface. Cyanixia socotrana was previously assigned to Babiana because of superficial similarities in morphology, including plicate leaves and blue flowers, thought at the time to be bilabiate, although now known to be actinomorphic and rotate. DNA sequence analysis using the chloroplast gene matK confirms that Babiana is a monophyletic assemblage, whereas B. socotrana is sister to the Lapeirousia/Savannosiphon clade of sub-Saharan Africa. The latter shares axillary corm ontogeny with the southern African Micranthus, Thereianthus, and Watsonia, in contrast to the more common situation in Crocoideae (including Babiana) in which the corm develops from the base of the flowering stem. The tropical African Zygotritonia, which also has axillary corm development, shares with Cyanixia a trisulcate pollen grain, but it differs markedly from that genus in its small, zygomorphic flower, undivided style, and basic chromosome number x=8. Cyanixia is here described as a new monotypic genus of Crocoideae, probably most closely allied to Savannosiphon, also a monospecific genus.