Metschnikowia continentalisvar.borealis,Metschnikowia continentalisvar.continentalis, andMetschnikowia hibisci, new heterothallic haploid yeasts from ephemeral flowers and associated insects

Abstract

Several strains of three new taxa of haploid heterothallic yeasts have been isolated from various ephemeral flowers and associated insects in North and South America and Australia. Metschnikowia continentalis comprises two varieties and is a close relative of Metschnikowia hawaiiensis. Like the latter, it produces giant ascospores and lives in association with the insects that colonize flowers of the family Convolvulaceae. These species exhibit an unusual asymmetrical mating, but their rare asci are sterile. The varieties of M. continentalis undergo unlimited mating, but ascospores are rarely formed. Metschnikowia continentalis var. continentalis was isolated in central Brazil and is thought to occur across South America.Metschnikowia continentalis var. borealis was recovered in the Great Lakes area and may represent a North American population. Metschnikowia hibisci was found in the flowers and insects of various Hibiscus species in the Australian states of New South Wales and Queensland but appeared to be absent in members of the Convolvulaceae growing in the same areas. The latter forms intermediate-sized ascospores and one of its mating types forms conjugation tubes in the presence of cells of other Metschnikowia species. The three taxa share with M. hawaiiensis a large deletion in the D2 region of their large ribosomal DNA subunit, but in M. hibisci, the variable domain of the D2 region shares little, if any, sequence similarity with others. The type cultures are as follows:M. continentalis var. continentalis strains UFMG96-173 (h+, CBS8429) and UFMG96-179 (h-, CBS8430); M. continentalis var. borealis strains UWO(PS)96-104.2 (h+, CBS 8431) and UWO(PS)96-101.1 (h-, CBS8432); and M. hibisci strains UWO(PS)95-797.2 (h+, CBS8433) and UWO(PS)95-805.1 (h-, CBS8434).Key words: Metschnikowia, yeast, Convolvulaceae, Hibiscus, geographic speciation.