Lactifluus piperatus (Russulales, Basidiomycota) and allied species in Western Europe and a preliminary overview of the group worldwide

The large, white milkcaps of Lactifluus section Piperati are well known in the northern hemisphere. Historically, there was extensive debate about the number of European representatives and the diagnostic characteristics that delimit the species. Combining a morphological approach with a phylogenetic study, we aimed to resolve the problems in this section in Europe. Secondly, a molecular analysis of worldwide representatives of Lactifluus section Piperati was carried out, to verify whether there is intercontinental conspecificity. We compared nuclear ITS and LSU rDNA, nuclear protein-coding rpb2 and mitochondrial protein-coding atp6 genealogies to delimit species, using a concatenation of genes, along with Bayesian species delimitation for the European dataset. The phylogenetic analyses show the existence of two species in Europe: Lactifluus piperatus and Lactifluus glaucescens. Morphologically, the frequently used characteristics of the colouration of the latex and the macrochemical reactions of latex and context appear not to be useful as diagnostic characteristics to discriminate the species, but the microscopical characters of the pileipellis are informative. The preliminary overview of the section worldwide shows that it comprises at least 10 possible species divided over three clades, and that there is no intercontinental conspecificity.