Importance of seasonal variation in Hawaiian mushroom (Agaricomycetes) basidiomata production for biodiversity discovery and conservation

The Hawaiian Islands have a relatively well-known funga for a tropical location, yet there are over 400 species of mushrooms (Agaricomycetes) in the archipelago that remain to be documented. Importantly, the International Union for Conservation of Nature (IUCN) recently evaluated six mushrooms endemic to the islands as threatened with extinction. To improve detection of mushrooms for biodiversity discovery and better monitor threatened species in the archipelago—where many localities lack strong annual precipitation patterns associated with an obvious season for increased mushroom basidiomata production—we examined the phenology of Hawaiian mushrooms. Monthly richness was determined from a literature review and abundance from online data repositories. Phenological patterns were separately explored for native species and differing elevation and annual precipitation categories. Despite relatively consistent monthly temperatures and areas with regular monthly rainfall, we found Hawaiian mushrooms generally exhibit uneven temporal patterns in basidiomata production: richness and abundance are generally highest in January and lowest from February to April, then usually increase from May to July and remain at elevated levels through December. This pattern does not occur when considering native species richness only, nor when examining abundance data stratified by elevation and annual rainfall categories. Increased monthly basidiomata abundance in low elevation (<1,000 m), dry (< 1,000 mm rainfall/year) locations on O‘ahu and low, mesic (1,000–2,500 mm rainfall/year) locations on O‘ahu and Kaua‘i are positively correlated with increased monthly rainfall. Phenology of macrofungal sporocarp production should potentially be included in species threat assessments by the IUCN to increase detection via traditional surveying methods.