Two new yeasts from flowers in northern Thailand

The genus Papiliotrema, in the family Rhynchogastremataceae, comprises basidiomycetous yeasts and is distributed worldwide. Its diversity nonetheless remains poorly known, because yeasts form no fruiting bodies — they cannot be collected in a forest or recognised from a photograph, they have to be isolated and cultured.

Chanaporn Kathongthung's team isolated six Papiliotrema strains from the flowers of five plants: Allamanda cathartica, Bidens pilosa, Cananga odorata, an Oncidium orchid and Plumeria obtusa. The material came from Chiang Mai Province in northern Thailand and was collected in 2024.

The conclusion rests on an integrative approach: multilocus phylogenetic analysis of five markers — ITS, the D1/D2 domains of the ribosomal large subunit, rpb1, rpb2 and tef1-α — combined with detailed phenotypic characterisation. The strains proved to represent two new species: Papiliotrema anthoicola, holotype SDBR-CMU883, and P. floralis, holotype SDBR-CMU888. The analysis separates them clearly from the other species in the genus.

The habitat itself is the interesting part of this result. A flower tends to be treated as a surface things pass over, whereas nectar and pollen form an environment rich in sugars, with variable pH and osmolarity, colonised by a specialised microbial community carried by insects. Floral yeasts alter the composition of nectar and, through it, potentially the behaviour of pollinators.

The species names say so outright: anthoicola means "dwelling in a flower", and floralis simply "of flowers". It is a case where the specific epithet doubles as a description of the ecology.

The strain numbers quoted in the description are worth noticing. For macrofungi the nomenclatural type is a dried specimen in a herbarium. For yeasts the type is often a living culture held in a collection, here under the accessions SDBR-CMU883 and SDBR-CMU888.

The difference is practical rather than formal. A living culture can be sent to another team, resequenced, characterised physiologically and used in assays. The price is the duty of maintaining a collection: a culture nobody looks after dies, and the possibility of checking the description dies with it.

What the paper establishes

Papiliotrema anthoicola and P. floralis were described from six strains isolated in 2024 from flowers of five plants in Chiang Mai: Allamanda cathartica, Bidens pilosa, Cananga odorata, Oncidium sp. and Plumeria obtusa. The authors integrated culture phenotype with ITS, D1/D2 LSU, rpb1, rpb2 and tef1-α; holotypes are represented by SDBR-CMU883 and SDBR-CMU888. This multilocus approach matters because similar yeasts should not be separated solely by colony colour or one barcode. Isolation from a flower tells us where culturable cells were recovered under study conditions. It does not demonstrate flower specialisation, persistent nectar residence, or a beneficial or harmful effect on pollinators. Six strains from one region cannot delimit complete distribution, abundance, host range or conservation status.