Stauro- and scolecoconidia in floral and honeydew honeys

Forty-four samples of floral and honeydew honeys from Croatia, Greece, Italy, Mexico, New Zealand, Portugal, South Africa, Spain and Tanzania were microscopically examined for fungal spores. Most of the floral honeys were dominated by yeast cells of Metschnikolvia reukaufii and contained very few conidia of hyphomycete species. By contrast, honeydew honeys contained scoleco- and stauroconidia belonging to more than 30 hyphomycete species, most of them previously reported from rainwater on living trees. Most belonged to the genera Tripospermum, Retiarius and Trinacrium. Their concentrations were highest in the honeydew honey from Abies alba and Picea excelsa. Conidia belonging to species of Camposporium, Ceratosporium, Dwayaangam, Tricellula, Tricladium and Trifurcospora, well-known litter-inhabiting fungi in terrestrial and/or aquatic habitats were encountered. Some other conidia probably belonged to species of Articulospora, Curucispora, Gyoerffyella, Lemonniera and Varicosporium, also well-known Ingoldian fungi from lotic ecosystems. The assemblages of fungal spores in honeydew honeys may provide important information on the geographical distribution of "canopy fungi". In addition, the results of this study support Carroll's theory on the existence of a fungal group termed "arboreal aquatic hyphomycetes" or "canopy fungi". Although their function in canopies is presently unknown, evidence accumulating in the literature suggests their widespread occurrence in the phyllosphere.