Metschnikowia drakensbergensis sp. nov. and Metschnikowia caudata sp. nov., two 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, eleven strains were found to represent two novel species. Morphological and physiological characteristics and sequence analyses of the D1/D2 large subunit rRNA gene, 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. 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 M. proteae, with which mating reactions and single-spored asci were observed. Metschnikowia caudata sp. nov. was isolated from nectar of P. dracomontana, P. roupelliae, P. subvestita and a honey bee, and is a sister species to Candida hainanensis and M. lopburiensis. Analyses of the four genes demonstrated the existence of three separate phylotypes. Intraspecies matings lead 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 is discussed in terms of host plant and insect host species. The type cultures are: Metschnikowia drakensbergensis (type strain EBD-CdVSA09-2T=CBS 13649T=NRRL Y-63721T, MycoBank no. MB809688; allotype EBD-CdVSA10-2A=CBS13650A=NRRL Y-63720A); and Metschnikowia caudata (type strain EBD-CdVSA08-1T=CBS 13651T=NRRL Y-63722T, MycoBank no. MB809689; allotype EBD-CdVSA57-2A=CBS 13729A=NRRL Y-63723A)