Molecular phylogeny of Laetiporus and other brown rot polypore genera in North America

Abstract

Phylogenetic relationships were investigated among North American species of Laetiporus, Leptoporus, Phaeolus, Pycnoporellus and Wolfiporia using ITS, nuclear large subunit and mitochondrial small subunit rDNA sequences. Members of these genera have poroid hymenophores, simple septate hyphae and cause brown rots in a variety of substrates. Analyses indicate that Laetiporus and Wolfiporia are not monophyletic. All North American Laetiporus species formed a well supported monophyletic group (the “core Laetiporus clade” or Laetiporus s.s.) with the exception of L. persicinus, which showed little affinity for any genus for which sequence data are available. Based on data from GenBank, the southern hemisphere species L. portentosus also fell well outside the core Laetiporus clade. Wolfiporia dilatohypha was found to represent a sister group to the core Laetiporus clade. Isolates of Phaeolus, Pycnoporellus and members of the core Laetiporus clade all fell within the Antrodia clade of polypores, while Leptoporus mollis and Laetiporus portentosus fell within the phlebioid clade of polypores. Wolfiporia cocos isolates also fell in the Antrodia clade, in contrast to previous studies that placed W. cocos in the core polyporoid clade. ITS analyses resolved eight clades within Laetiporus s.s., three of which might represent undescribed species. A combined analysis using the three DNA regions resolved five major clades within Laetiporus s.s.: a clade containing conifer-inhabiting species (“Conifericola clade”), a clade containing L. cincinnatus (“Cincinnatus clade”), a clade containing L. sulphureus s.s. isolates with yellow pores (“Sulphureus clade I”), a clade containing L. sulphureus s.s. isolates with white pores (“Sulphureus clade II”) and a clade containing L. gilbertsonii and unidentified isolates from the Caribbean (“Gilbertsonii clade”). Although there is strong support for groups within the core Laetiporus clade, relationships among these groups remain poorly resolved.

• evolution
• Fungi
• Macrohyporia
• Polyporaceae
• Poria
• root rot
• sulfur shelf
• Wolfiporia extensa

We thank Don Hemmes of the University of Hawai’i at Hilo for providing Laetiporus isolates from Hawai’i; D. Jean Lodge of the USDA-Forest Service, Center for Forest Mycology Research, for providing isolates and fruiting bodies of Laetiporus and “Polyporus talpae” from Puerto Rico; and Thomas J. Volk of the University of Wisconsin at La Crosse for collecting many of the Laetiporus specimens used in this study. We also thank David Hibbett and Zheng Wang of Clark University for providing sequences of Sparassis as well as access to large sequence databases of homobasidiomycetes. We are grateful for the help of David Hibbett and Karen Nakasone; they provided assistance with phylogenetic analyses and helpful advice on previous versions of this manuscript.