Variation of subterranean fungal community structure across substrate age and elevation in native forests on Hawai'i Island, USA

Fungi are essential to ecosystem function, playing a variety of roles. Soil fungi in particular have multiple ecological roles; they may function as mychorrhizae, saprophytes, and pathogens. Hawaiian microfungi are poorly documented and poorly understood; we know little about their population structure and how they respond to environmental gradients. Furthermore, no study has examined soil fungi in Hawai'i. This study investigates the variation of underground fungal communities over wide environmental gradients (1,000-5,000 MAP; 10-22ºC MAT) and short geographic distances on Mauna Loa volcanic substrates. Soil samples (100) were collected at ten sites, on dissimilar aged lava flows, and at five elevations in native forests on Hawai'i Island. We analyzed ribosomal RNA internal transcribed spacer region 1 (ITS1) sequences produced from the Ion Torrent "next-generation" sequencing platform. We used the bioinformatics program MOTHUR to trim and analyze our reads. We elucidate these communities by reporting Shannon diversity, Simpson diversity, Fisher's alpha diversity, and richness of Operational Taxonomic Units (OTUs). We recovered a total of 15,869 OTUs from over 3 million reads. We found that elevations of 100 meters were less OTU-rich and less diverse in terms of Fisher's alpha when compared to all other elevations. We found no significant effect of substrate age on richness or diversity. We also found no significant effect of elevation or substrate age on Shannon and Simpson diversities. The phylum Zygomycota contained the 2 most abundant individual OTUs in the overall landscape, while the phylum Ascomycota contained the majority of OTUs and was the most abundant group overall. The most dominant genera recovered at each site were Mortierella, Archaeorhizomyces, and Sphaerosporella. This novel study will allow further investigations of soil fungal communities in Hawai`i.