Metschnikowia drakensbergensis sp. nov. and Metschnikowia caudata sp. nov., endemic yeasts associated with Protea flowers in South Africa

Abstract

In a taxonomic study of yeasts recovered from nectar of flowers and associated insects in South Africa, 11 strains were found to represent two novel species. Morphological and physiological characteristics and sequence analyses of the large-subunit rRNA gene D1/D2 region, as well as the actin, RNA polymerase II and elongation factor 2 genes, showed that the two novel species belonged to the genus Metschnikowia. Metschnikowia drakensbergensis sp. nov. (type strain EBD-CdVSA09-2T = CBS 13649T = NRRL Y-63721T; MycoBank no. MB809688; allotype EBD-CdVSA10-2A = CBS13650A = NRRL Y-63720A) was recovered from nectar of Protea roupelliae and the beetle Heterochelus sp. This species belongs to the large-spored Metschnikowia clade and is closely related to Metschnikowia proteae, with which mating reactions and single-spored asci were observed. Metschnikowia caudata sp. nov. (type strain EBD-CdVSA08-1T = CBS 13651T = NRRL Y-63722T; MycoBank no. MB809689; allotype EBD-CdVSA57-2A = CBS 13729A = NRRL Y-63723A) was isolated from nectar of Protea dracomontana, P. roupelliae and P. subvestita and a honeybee, and is a sister species to Candida hainanensis and Metschnikowia lopburiensis. Analyses of the four sequences demonstrated the existence of three separate phylotypes. Intraspecies matings led to the production of mature asci of unprecedented morphology, with a long, flexuous tail. A single ascospore was produced in all compatible crosses, regardless of sequence phylotype. The two species appear to be endemic to South Africa. The ecology and habitat specificity of these novel species are discussed in terms of host plant and insect host species.