Diversity and Phylogeny of Novel Cord-Forming Fungi from Borneo

Cord-forming (CF) fungi are found worldwide; however, tropical CF fungi are poorly documented. They play an essential role in forest ecosystems by interconnecting nutrient resources and aiding in the decomposition of plant matter and woody litter. CF fungi samples were collected from two forest conservation sites in the Sabah region of Malaysian Borneo. Sequencing and phylogenetic analysis of the ribosomal rRNA gene array 18S to 28S region from cords collected placed all of the collected specimens in Agaricomycetes (Basidiomycetes), specifically within the orders Trechisporales, Phallales, Hymenochaetales, Polyporales, and Agaricales. Comparison of the cord-derived sequences against GenBank and UNITE sequence databases, as well as phylogenetic analyses, revealed they were all novel sequences types. Many of these novel lineages were found to be closely related to other basidiomycetes commonly found in tropical forests, suggesting a large undiscovered tropical fungal diversity in Borneo that has been detected independently of sampling fruiting bodies. We show how these sequence types relate to the morphologies of the cords from which they were sampled. We also highlight how rapid, small-scale sampling can be a useful tool as an easy and relatively unbiased way of collecting data on cord-forming fungi in difficult-to-access, complex forest environments, independently of locating and sampling sporophores.