A description is given of a new yeast genus, Phaffia, represented by P . rhodozyma sp. nov., to accomodate nine yeast strains isolated in Japan and one in Alaska, all from exudates of deciduous trees. The type strain of P. rhodozyma is UCD (FS&T) 67-210 (= ATCC 24202 = CBS 5905). Phafia, named in recognition of the contributions of Herman Jan Phaff to yeast taxonomy and ecology, is a carotenoid-producing, fermentative yeast of the Deuteromycotina (Blastomycetes) , whose properties indicate a basidiomycetous origin. A comparison is made between Phaffia and other yeast genera to which it might be related.In surveys of yeasts in tree exudates (slime fluxes) in Japan and in the Pacific Northwest of North America (16), we isolated 10 similar yeast strains that belong to a new species which represents a new genus. This yeast produces carotenoid pigments, reproduces vegetatively by budding, and lacks, as far as we have been able to determine, a sexual life cycle. It could not be accommodated in the genus Rhodotorula Harrison because species in that genus are nonfermentative, whereas the isolates from tree exudates ferment several sugars. In an earlier publication (16), this yeast was tentatively named Rhodozyma montanae. However, a Latin diagnosis, as required by the rules of the International Code of Botanical Nomenclature, was not given, and this binomial is therefore a nomen nudum. The intent of this paper is to give a complete description, to discuss the taxonomic relationships of the new organism, and to provide it with a validly published name. MATERIALS AND METHODSSamples of exudates were collected in new plastic vials or bags. Usually within 6 to 18 h after collection, a loopful of the slimy exudate was streaked directly on 5% malt agar acidified with hydrochloric acid to pH 3.7. If the sample was in a dehydrated condition, it was removed from the tree with a specially made chisel sterilized in alcohol. It was then rehydrated with a small amount of sterile water for a suitable length of time before streaking. The inoculated plates were stored at room temperature ranging from about 15 to 25 C. On most of the plates, relatively few fungi appeared, but many of the samples yielded significant numbers of bacterial colonies in spite of the low pH of malt agar. The plates were inspected with a dissecting microscope after 3 to 6

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JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org. Abstract. A survey was made in the SonoranDesert of yeasts living in the decaying arms of five species of cereus cacti and the four species of Drosoplhila that utilize them as host plants. The most common yeasts among 132 isolates from the cacti and 187 isolates from the flies, respectively, were: Pichia membranaefaciens (45% and 67%), Candida ingens (17% and 4%), Torulopsis sonorensis (12% and 11%), and Cryptococcus cereanus (8% and 7%). Eighty-eight percent of the 66 initial isolates of P. membranaefaciens from Drosophila pachea and its host, senita cactus, assimilated D-xylose while only 12% of the remaining 257 initial isolates did so. Nineteen of the 20 isolates of T. sonorensis from flies were found in Drosophila mojavensis and 12 of the 14 isolates of C-yptococcus cereanus came from D. pachea. The highest mean number of yeast species per cactus was 2.77 ? 0.68 in organpipe cactus and per fly was 1.63 + 0.53 in D. pachea. The flies usually carried fewer yeast species than were found in the host plant but D. pachea had almost the same mean and variance as its host, senita cactus, which had 1.64 ? 0.40. Yeast species diversity and average niche overlap have the following rank order among habitats and localities: temperate trees > temperate flies > tropical flies > desert cacti > desert flies. Habitat diversity and average niche width show: tropical flies > temperate flies and desert cacti > desert flies and temperate trees. The physiological properties of the desert yeasts are most similar to those of the tropical yeast. However, desert yeasts have similarities with yeasts of temperate trees. Both have low fermentative ability and high assimilation ability of several alcohols and acids. The genus Pichia is by far the most common yeast genus associated with Drosophila in all habitats analyzed (36% of 1,426 isolates).

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