Species and genera in Aleurodiscus sensu lato as viewed from the Southern Hemisphere

Phylogenetic relationships of 12 species in <i>Aleurodiscus</i> sensu lato (Stereaceae, Russulales) described from the Patagonian forests of Chile and Argentina were investigated based on sequences of nuc rDNA internal transcribed spacer region ITS1-5.8S-ITS2 (ITS) and the D1–D2 domains of nuc 28S rDNA (28S). A new genus and a new species are presented, and 10 new combinations proposed. The genus <i>Gloeosoma</i> is shown to be phylogenetically well supported and morphologically circumscribed; it includes <i>G. vitellinum</i> (type species), <i>G. mirabile</i>, comb. nov., <i>G. zealandicum</i>, comb. nov., and <i>Gloeosoma decorticans</i>, sp. nov., which is newly described from Chile. The new genus <i>Stereodiscus</i> is proposed to accommodate a group of taxa characterized by an austral distribution and morphologically by smooth, thin-walled, amyloid basidiospores and a lack of gloeocystidia and acanthocystidia; three species develop <i>Stereum</i>-like basidiomata and two species present discoid ones. The new genus includes the species formerly known as <i>Aleurodiscus antarcticus, A. limonisporus, A. parmuliformis, A. patagonicus</i>, and <i>A. triviale</i>. Specimens of <i>Stereodiscus parmuliformis</i> (<i>A. parmuliformis</i>) from New Zealand (where it was originally described) and southern Chile are shown to be phylogenetically conspecific, which confirms its presence in Patagonia. <i>Gloeosoma</i> and <i>Stereodiscus</i> are shown to be distantly related to <i>Aleurodiscus</i> s. str. and other genera in Stereaceae. The new combinations <i>Aleurocystidiellum bernicchiae, Aleurocystidiellum hallenbergii</i>, and <i>Acanthobasidium quilae</i> are proposed based on morphology and phylogenetic analyses, and <i>Aleurodiscus cerussatus</i> is shown to be a cryptic species complex.