Taxonomy and multigene phylogeny reveal Inonotus cerradensis (Hymenochaetales, Hymenochaetaceae) as a new species from Brazil

Abstract Inonotus is a hymenochaetoid genus with worldwide distribution, known for its wood-decaying species. Since Karsten proposed it in 1879, significant revisions have been made to its circumscription, and several species complexes are currently being reevaluated through integrative taxonomic approaches. Although rare, some species in the genus have a described anamorphic stage. Historically, dense, ferruginous, pulvinate masses of chlamydospores attached to trunks and branches have been attributed to Ptychogaster cubensis , the anamorph of Inonotus rickii . However, during a survey of wood-inhabiting fungi in Central Brazil, similar structures were found on living and dead trees. Long-term observations revealed that the fungus grew annually on the same host and adjacent trees and exhibited an ecological relationship with beetles that fed on its structures and dispersed chlamydospores to nearby hosts. The collected sporomata were isolated and characterized morphologically and phylogenetically using ITS, LSU, RPB2 , and TEF1-α partial sequences. Based on these analyses, we describe a new species represented in its anamorphic stage, Inonotus cerradensis sp. nov. The new species is characterized by sporomata formed by beard-like rhizomorphs bearing dense clusters of globose, soft, fragile chlamydospores that easily disintegrate upon touch, rhizomorphs cylindrical to flattened, with superficial outward-projecting and hyphal setae. We also conducted a detailed review of specimens representing both stages of I. rickii to refine its morphological circumscription. Both species form distinct and well-defined clades within Inonotus s. str. and differ mainly in sporomata organization: loose, rhizomorph-supported structures characterize the new species, whereas compact, stratified, and concentrically organized sporomata correspond to the anamorph of I. rickii . This study highlights how integrative taxonomy clarifies species boundaries within Inonotus and advances the understanding of the genus and its ecology in Neotropical environments.