Survey of corticioid fungi in North American pinaceous forests reveals hyperdiversity, underpopulated sequence databases, and species that are potentially ectomycorrhizal

ABSTRACT

The corticioid fungi are commonly encountered, highly diverse, ecologically important, and understudied. We collected specimens in 60 pine and spruce forests across North America to survey corticioid fungal frequency and distribution and to compile an internal transcribed spacer (ITS) database for the group. Sanger sequences from the ITS region of vouchered specimens were compared with sequences on GenBank and UNITE, and with high-throughput sequence data from soil and roots taken at the same sites. Out of 425 high-quality Sanger sequences from vouchered specimens, we recovered 223 distinct operational taxonomic units (OTUs), the majority of which could not be assigned to species by matching to the BLAST database. Corticioid fungi were found to be hyperdiverse, as supported by the observations that nearly two-thirds of our OTUs were represented by single collections and species estimator curves showed steep slopes with no plateaus. We estimate that 14.8–24.7% of our voucher-based OTUs are likely to be ectomycorrhizal (EM). Corticioid fungi recovered from the soil formed a different community assemblage, with EM taxa accounting for 40.5–58.6% of OTUs. We compared basidioma sequences with EM root tips from our data, GenBank, or UNITE, and with this approach, we reiterate existing speculations that Trechispora stellulata is EM. We found that corticioid fungi have a significant distance-decay pattern, adding to the literature supporting fungi as having geographically structured communities. This study provides a first view of the diversity of this important group across North American pine forests, but much of the biology and taxonomy of these diverse, important, and widespread fungi remains unknown.

KEYWORDS:

• BLAST
• corticioid fungi
• ectomycorrhizal
• Picea
• Pinus
• sequence survey

Acknowledgments

We thank the following people for helping us with site selection and local logistics: D. Lee Taylor, Peggy Moore, Alison Colwell, Jennie Haus, Ben Becker, Matt Smith, Jason Hoeksema, Erik Lilleskov, Richard Wilson, Cathy Cripps, Don Bachman, Melanie Jones, Dan Durall, Steve Miller, Jeff Mitton, Noah Fierer, Robert Marra, Anthony D’Amato, Chuck Kramer, Joshua Kragthorpe, and Shawn Fraver, and we thank Karen Nakasone for co-hosting the NAMA workshop on corticioids, which helped motivate this work. Funding was provided by National Science Foundation Dimensions of Biodiversity program (awards 1045658, 1046115, and 1046052).

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