Global diversity and phylogeny of Incrustoporiaceae (Polyporales, Basidiomycota) with an emphasis on <i>Skeletocutis</i>

This study presents the taxonomy and phylogeny of the family Incrustoporiaceae, based on comprehensive phylogenetic analyses utilising multi-gene data, including the internal transcribed spacer regions (ITS) and the large subunit of the nuclear ribosomal RNA gene (nLSU), for the accepted genera within Incrustoporiaceae. Additionally, a separate phylogenetic analysis focusing on the <i>Skeletocutis nivea</i> complex was performed using ITS sequences. A total of 20 new species within the genus <i>Skeletocutis</i> are described, namely <i>Skeletocutis crystallina</i>, <i>S. cunninghamiae</i>, <i>S. cylindrica</i>, <i>S. ellipsoidea</i>, <i>S. flavipora</i>, <i>S. latemarginata</i>, <i>S. liangdongii</i>, <i>S. monocotyledona</i>, <i>S. montanus</i>, <i>S. neoalbomarginata</i>, <i>S. oceanica</i>, <i>S. ochraceocarpa</i>, <i>S. quercicola</i>, <i>S. sinica</i>, <i>S. sinoalbomarginata</i>, <i>S. sinochrysella</i>, <i>S. subamorpha</i>, <i>S. subdiluta</i>, <i>S. subkrawtzewii</i>, and <i>S. sublilacina</i>. Detailed illustrated descriptions, voucher specimens, hosts, distribution, diagnoses, and remarks are provided for these 20 new species. Additionally, two new combinations are proposed: <i>S. minutula</i> and <i>Tyromyces subodorus</i>. Notably, our discoveries of <i>S. oceanica</i> and <i>S. subdiluta</i> in Australia underscore the significance of expanding research on <i>Skeletocutis</i> diversity in the Southern Hemisphere, where reports are scarce. Phylogenetic analyses also clarified the taxonomic positions of <i>Skeletocutis</i> and <i>Tyromyces</i> within the Incrustoporiaceae family, showing that <i>Tyromyces</i> is nested within the polyphyletic <i>Skeletocutis</i> clade. The morphological distinctions between <i>Skeletocutis</i> and <i>Tyromyces</i>, as well as between <i>Skeletocutis</i> and <i>Sidera</i>, are also discussed.