Visiting Russula (Russulaceae, Russulales) with samples from southwestern China finds one new subsection of R. subg. Heterophyllidia with two new species

Abstract

Using specimens collected from subtropical pine-fagaceous mixed forests and phylogenetic analysis of DNA sequence data of ITS, 28S rDNA, rpb2 and tef1, we describe two new species, R. maguanensis and R. substriata, in R. subg. Heterophyllidia, subsect. Substriatinae subsect. nov. Russula maguanensis and R. substriata are similar to Indian R. shingbaensis in the tuberculate-striate pileus and spores with isolated warts but have more vividly coloured pileus and associate with pines and/or fagaceous trees rather than with Abies. In our multi-gene phylogeny, the new subsection and a representative of tropical African R. subsect. Aureotactinae compose one of the four major clades of R. subg. Heterophyllidia, the three remaining ones corresponding to R. sect. Heterophyllae, R. sect. Ingratae and R. subsect. Cyanoxanthinae. The overall characters of this new section combine those of some other sections in the same subgenus: mostly tuberculate-striate but more vivid pileus, spores with isolated warts, orthochromatic pileipellis with abundant erect aggregate mucronate pileocystidia in the suprapellis but absent in the subpellis and numerous cystidioid hyphae at the bottom of subpellis and trama beneath it. It differs from its sister clade R. subsect. Aureotactinae in lacking the intense yellowing of surface and context of their fruiting bodies and having pileal cystidioid elements clearly separated by the loose tissue of subpellis from the pileocystidia at the pileus surface. In order to compare our two new species with recently described Asian species and investigate their geographical distributions, we produced an ITS genealogy including also environmental sequences. This ITS genealogy suggests that R. subsect. Substriatinae includes at least seven potential species, shows an amphi-pacific distribution and its members associate with at least four families of host trees.