A new section, Lactifluus section Neotropicus (Russulaceae), and two new Lactifluus species from the Atlantic Forest, Brazil

Lactifluusis a monophyletic genus of ectomycorrhizal fungi with about 200 described species classified in four subgenera:L.subg.Gymnocarpus,L.subg.Lactariopsis,L.subg.Lactifluus, andL.subg.Pseudogymnocarpus. CurrentlyL.subg.Lactariopsisis considered monophyletic with approximately 57 species described and classified in four sections:Albati,Edules,Lactariopsis, andRussulopsidei.There are few species ofL.subg.Lactariopsisdescribed from the Neotropical region, however local mycologists commonly collect specimens of this subgenus during their mycological surveys. The goals of the present study are to evaluate the phylogenetic and morphological relationships of the species fromL.subg.Lactariopsisfound in Brazil, to contribute to the knowledge ofLactifluusin Neotropical ecosystems by describing a new section in this subgenus and two new species from Brazil, and to documentL. neotropicusas a new record from Brazil. Based on morphological and phylogenetic evidence we proposeLactifluussect.Neotropicusas a new section andLactifluus catarinensisandL. marielleaeas two new species in this section. We provide a key to the species ofL.sect.Neotropicus, which is shown to be a monophyletic group of Neotropical species withinL.subg.Lactariopsis. The most striking characteristic of several species inL.subg.Lactariopsisis the secondary angiocarpic development, not present in the other subgenera. Species with a secondary veil can be found in two lineages that diversified more recently than the rest of the genus:L.sect.LactariopsisandL.sect.Neotropicus.Species that show morphological affinities with the two new species inL. sect.Neotropicusdescribed here are commonly found and we expect a greater diversity to be revealed of this section in the Neotropical region.