Phylogenetic and morphological studies of Meripilaceae (Polyporales) from South America: a reevaluation of the genera <i>Henningsia, Meripilus, and Physisporinus</i>

This study presents a comprehensive phylogenetic analysis of the genus <i>Meripilus</i> and its allied genera <i>Henningsia</i> and <i>Physisporinus</i> within the Meripilaceae family, in the broader context of the residual polyporoid clade. The three genera are morphologically similar and characterized by resupinate to pileate basidiomes that harden and often darken upon drying, a monomitic hyphal structure, simple-septate generative hyphae, and globose to ovoid basidiospores, with variable presence of cystidia. Species in <i>Henningsia</i> and <i>Meripilus</i>, in turn, present gloeopleurous hyphae in the context and large, multipileate basidiomes. Recent studies have indicated that <i>Physisporinus</i>, as currently defined, is not monophyletic, with <i>Meripilus</i> nested within it. Phylogenetic analysis based on four molecular markers confirmed the paraphyletic nature of <i>Physisporinus</i>, with <i>Meripilus</i> and <i>Henningsia</i> both nested within it. Morphological examinations of specimens collected in South America, along with revisions of type specimens, show that this segregation is not natural and causes nomenclatural problems. We propose to transfer all species currently placed in <i>Physisporinus</i> into <i>Meripilus</i>, thereby preventing the division of the genus into morphologically indistinguishable groups. As a result of this reclassification, we propose 35 new combinations in <i>Meripilus</i> and describe three new species from South America.