Flowers as a reservoir of yeast diversity: description of Wickerhamiella nectarea f.a. sp nov., and Wickerhamiella natalensis f.a. sp nov from South African flowers and pollinators, and transfer of related Candida species to the genus Wickerhamiella as new combinations

Flowers offer favourable microenvironments for yeast growth, and are increasingly recognised as a rich source of novel yeast species. Independent surveys of yeasts associated with flowers and pollinators in South Africa led to the discovery of 38 strains of two new species. Physiological profiles and analysis of the internal transcribed spacer and the D1/D2 domains of the large subunit rRNA gene showed that they represent two novel species that belong to the Wickerhamiella clade. We describe the species as Wickerhamiella nectarea f.a. sp. nov. (type strain EBDCdVSA11-1T, CBS 14162(T), NRRL Y-63791(T)) and W. natalensis f.a. sp. nov. (type strain EBDCdVSA7-1(T), CBS 14161(T), NRRL Y-63790(T)). We extend the known range of flower-associated Wickerhamiella species to South Africa and discuss the ecology and phylogenetic relationships of the clade in relation to its host species and biogeography. Examination of growth characteristics supports that the Wickerhamiella clade exhibits a high degree of evolutionary lability, and that specialisation to different niches may occur rapidly. We review the current status of floral yeast biodiversity and nectar as a reservoir of species diversity, and the importance of pollinators and biogeography. In addition, 18 species formerly assigned to the genus Candida are reassigned formally to the genus Wickerhamiella.