Looks can be deceiving: the deceptive milkcaps (Lactifluus, Russulaceae) exhibit low morphological variance but harbour high genetic diversity

Three New Species of Lactifluus (Basidiomycota, Russulaceae) from Guizhou Province, Southwest China

Lactifluus is a distinct genus of milkcaps, well known as ectomycorrhizal fungi. The characteristics of the genus Lactifluus include grayish-yellow, orange to orange-brown, or reddish-brown pileus, white latex from the damaged lamellae, discoloring to a brownish color, reticulate spore ornamentation, lampropalisade-type pileipellis, and the presence of lamprocystidia. Guizhou Province is rich in wild mushroom resources due to its special geographical location and natural environment. In this study, three novel Lactifluus species were identified through the screening of extensive fungal resources in Suiyang County, Guizhou Province, China, sampled from host species of mostly Castanopsis spp. and Pinus spp. Based on critical morphology coupled with nuclear sequences of genes encoding large subunit rRNA, internal transcribed spacer, and RNA polymerase II, these new species, Lactifluus taibaiensis, Lactifluus qinggangtangensis, and Lactifluus jianbaensis, were found to belong to Lactifluus section Lactifluus. A comparison with closely related species, Lactifluus taibaiensis was distinguished by its lighter-colored pileus, different colors of lamellae, and more subglobose basidiospores; Lactifluus jianbaensis was identified by the height of the spore ornamentation and its subglobose basidiospores; and Lactifluus qinggangtangensis was characterized by having smaller basidiospores, ridges, and pleurolamprocystid.

Paxilloboletus gen. nov., a new lamellate bolete genus from tropical Africa

This study presents Paxilloboletus gen. nov., a new lamellate bolete genus represented by two tropical African species, Paxilloboletus africanus sp. nov. and Paxilloboletus latisporus sp. nov. Although the new taxa strongly resemble Paxillus (Paxillaceae), they lack clamp connections and form a separate generic clade within the Boletaceae phylogeny. The new species are lookalikes, morphologically only separable by their spore morphology. Descriptions and illustrations of the new genus and new species are given, as well as comments on ecology, distribution, and morphological differences with other gilled Boletaceae.

Redelimitation of Heteroradulum (Auriculariales, Basidiomycota) with H.australiense sp. nov

Auriculariales accommodates species with diverse basidiomes and hymenophores. From morphological and phylogenetic perspectives, we perform a taxonomic study on Heteroradulum, a recently validated genus within the Auriculariales. The genus Grammatus is merged into Heteroradulum, and thus its generic type G.labyrinthinus is combined with Heteroradulum and G.semis is reaccepted as a member of Heteroradulum. Heteroradulumaustraliense is newly described on the basis of three Australian specimens. Heteroradulumyunnanense is excluded from this genus and its taxonomic position at the generic level is considered uncertain. Accordingly, the circumscription of Heteroradulum is re-delimited and the concept of this genus is adjusted by including irpicoid to poroid hymenophores and a hyphal system with clamp connections or simple septa. A key to all nine accepted species of Heteroradulum is presented.

Retiboletus (Boletaceae) in northern Thailand: one novel species and two first records

Morphological characters and multi-gene phylogenetic analyses were used to identify Retiboletus specimens collected in northern Thailand. Retiboletus brevibasidiatus is described as new to science, whereas R. fuscus and R. nigrogriseus are reported for the first time from Thailand. Retiboletus brevibasidiatus produces medium-sized basidiomes, with a dark blonde to clay pileus and densely reticulate stipe mostly on the upper part with pale yellow to chrome yellow basal mycelium. It is difficult to separate R. brevibasidiatus from other closely related species on the basis of macroscopic characters. However, the new species can be distinguished by microscopic characters, mostly the shorter basidia. The macro- and micro-morphology of the R. fuscus and R. nigrogriseus collections from Thailand fit well with the previous descriptions of materials from China and Japan. Detailed descriptions, molecular phylogeny, and illustrations of the three species are provided.

Taxonomic Revision of the Genus Lactifluus (Russulales, Basidiomycota) of South Korea

Lactifluus (Pers.) Roussel is an ectomycorrhizal genus that was recently recognized to be distinct from the genus Lactarius. To date, 226 Lactifluus species have been reported worldwide. Misidentification of Lactifluus species is common because of intraspecific morphological variation, cryptic diversity, and the limited number of taxonomic keys available. Molecular data are indispensable for species delimitation; a multilocus phylogenetic analysis showed that most Asian Lactifluus species are not conspecific with morphologically similar species present on other continents. In particular, Korea has misused European and North American Lactifluus names. In this study, we evaluated the taxonomy of Lactifluus in Korea using both morphological and multilocus molecular (ITS, nrLSU, rpb1, and rpb2) data. We examined 199 Lactifluus specimens collected between 1980 and 2016, and a total of 24 species across the four Lactifluus subgenera were identified. All Korean species are distinct and clearly separated from European and North American species. Five taxa corresponded to previously described species from Asia and the remaining 19 taxa are confirmed as new species. Herein, we provide keys to the Korean Lactifluus species within their subgenera, molecular phylogenies, a summary of diversity, and detailed description of the new species.

Enlightening the black and white: species delimitation and UNITE species hypothesis testing in the Russula albonigra species complex

Russula albonigra is considered a well-known species, morphologically delimited by the context of the basidiomata blackening without intermediate reddening, and the menthol-cooling taste of the lamellae. It is supposed to have a broad ecological range and a large distribution area. A thorough molecular analysis based on four nuclear markers (ITS, LSU, RPB2 and TEF1-α) shows this traditional concept of R. albonigra s. lat. represents a species complex consisting of at least five European, three North American, and one Chinese species. Morphological study shows traditional characters used to delimit R. albonigra are not always reliable. Therefore, a new delimitation of the R. albonigra complex is proposed and a key to the described European species of R. subgen. Compactae is presented. A lectotype and an epitype are designated for R. albonigra and three new European species are described: R. ambusta, R. nigrifacta, and R. ustulata. Different thresholds of UNITE species hypotheses were tested against the taxonomic data. The distance threshold of 0.5% gives a perfect match to the phylogenetically defined species within the R. albonigra complex. Publicly available sequence data can contribute to species delimitation and increase our knowledge on ecology and distribution, but the pitfalls are short and low quality sequences.

A short story of nearly everything in Lactifluus (Russulaceae)

Fungi are a large and hyper-diverse group with major taxa present in every ecosystem on earth. However, compared to other eukaryotic organisms, their diversity is largely understudied. Since the rise of molecular techniques, new lineages are being discovered at an increasing rate, but many are not accurately characterised. Access to comprehensive and reliable taxonomic information of organisms is fundamental for research in different disciplines exploring a variety of questions. A globally dominant ectomycorrhizal (ECM) fungal family in terrestrial ecosystems is the Russulaceae (Russulales, Basidiomycota) family. Amongst the mainly agaricoid Russulaceae genera, the ectomycorrhizal genus Lactifluus was historically least studied due to its largely tropical distribution in many underexplored areas and the apparent occurrence of several species complexes. Due to increased studies in the tropics, with a focus on this genus, knowledge on Lactifluus grew. We demonstrate here that Lactifluus is now one of the best-known ECM genera. This paper aims to provide a thorough overview of the current knowledge of Lactifluus, with information on diversity, distribution, ecology, phylogeny, taxonomy, morphology, and ethnomycological uses of species in this genus. This is a result of our larger study, aimed at building a comprehensive and complete dataset or taxonomic framework for Lactifluus, based on molecular, morphological, biogeographical, and taxonomical data as a tool and reference for other researchers. Citation: De Crop E, Delgat L, Nuytinck J, Halling RE, Verbeken A (2021). A short story of nearly everything in Lactifluus (Russulaceae). Fungal Systematics and Evolution 7: 133-164. doi: 10.3114/fuse.2021.07.07.

Lactifluus (Russulaceae) diversity in Central America and the Caribbean: melting pot between realms

Species of the ectomycorrhizal genus Lactifluus, and often entire sections, are typically unique to a single continent. Given these biogeographic patterns, an interesting region to study their diversity is Central America and the Caribbean, since the region is closely connected to and often considered a part of the North American continent, but biogeographically belong to the Neotropical realm, and comprises several regions with different geologic histories. Based on a multi-gene phylogeny and morphological study, this study shows that Central America, Mexico and the Caribbean harbour at least 35 Lactifluus species, of which 33 were never reported outside of this region. It was found that species from the Caribbean generally show affinities to South American taxa, while species from the Central American mainland generally show affinities to Northern hemispheric taxa. We hypothesise that host specificity and/or climate play a crucial role in these different origins of diversity. Because of these different affinities, Caribbean islands harbour a completely different Lactifluus diversity than the Central American mainland. The majority of species occurring on the islands can be considered endemic to certain islands or island groups. In this paper, detailed morphological descriptions are given, with a focus on the unique diversity of the islands, and identification keys to all hitherto described Lactifluus species occurring in Central America and the Caribbean are provided. One new section, Lactifluus sect. Nebulosi, and three new species, Lactifluus guadeloupensis, Lactifluus lepus and Lactifluus marmoratus are described.