Hortiboletus (the former Xerocomus rubellus species complex) is one of the most taxonomically critical and difficult genera for species identification in the family Boletaceae. Here, we provide a detailed morphological and molecular re-assessment of European and Levantine species of Hortiboletus. A new species, H. hershenzoniae, is described from Israel. It is sister to H. engelii and associated with the evergreen oak Quercus calliprinos and potentially also with Q. ithaburensis. Based on the sequence retrieved from INSDC, this species is also found in Lebanon. Accurate morphological descriptions, comprehensive sampling, type studies, biogeography, macro- and microphotographs and a historical overview on the nomenclatural issues surrounding H. rubellus, H. bubalinus, H. engelii, and H. hershenzoniae are given. An epitype collection is designated for H. rubellus. A key is provided for identification of the European and Levantine taxa. In addition, we propose a novel taxonomic combination Hortiboletus flavorubellus, which is conspecific with Boletus rubellus var. flammeus, based on the DNA barcoding and phylogenetic analysis of type material. Boletus harrisonii is also shown to be conspecific with H. campestris. A multilocus phylogenetic analysis of four markers (ITS, LSU, tef1-α, and rpb2) reveals that Hortiboletus is a sister genus to Xerocomellus. Using the Genealogical Concordance Phylogenetic Species Recognition method, at least 19 phylogenetic species and eight putative phylogenetic species of the genus Hortiboletus can be delimited. Based on multilocus analysis, it contains from 24 to 25 species-level clades worldwide, 17 out of which represent known species, one newly described and potentially six to seven undescribed species. Tandem repeat insertions within the ITS region (both in ITS1 and ITS2) are reported for the first time, not only in the genus Hortiboletus, but in the entire subfamily Boletoideae. Their identification and characterisation were based on Tandem Repeat Finder analysis and visual assessment of the ITS alignment.

The boletoid genera Butyriboletus and Exsudoporus have recently been suggested by some researchers to constitute a single genus, and Exsudoporus was merged into Butyriboletus as a later synonym. However, no convincing arguments have yet provided significant evidence for this congeneric placement. In this study, we analyze material from Exsudoporus species and closely related taxa to assess taxonomic and phylogenetic boundaries between these genera and to clarify species delimitation within Exsudoporus. Outcomes from a multilocus phylogenetic analysis (ITS, nrLSU, tef1-α and rpb2) clearly resolve Exsudoporus as a monophyletic, homogenous and independent genus that is sister to Butyriboletus. An accurate morphological description, comprehensive sampling, type studies, line drawings and a historical overview on the nomenclatural issues of the type species E. permagnificus are provided. Furthermore, this species is documented for the first time from Israel in association with Quercus calliprinos. The previously described North American species Exsudoporus frostii and E. floridanus are molecularly confirmed as representatives of Exsudoporus, and E. floridanus is epitypified. The eastern Asian species Leccinum rubrum is assigned here to Exsudoporus based on molecular evidence, and a new combination is proposed. Sequence data from the original material of the Japanese Boletus kermesinus were generated, and its conspecificity with L. rubrum is inferred as formerly presumed based on morphology. Four additional cryptic species from North and Central America previously misdetermined as either B. frostii or B. floridanus are phylogenetically placed but remain undescribed due to the paucity of available material. Boletus weberi (syn. B. pseudofrostii) and Xerocomus cf. mcrobbii cluster outside of Exsudoporus and are herein assigned to the recently described genus Amoenoboletus. Biogeographic distribution patterns are elucidated, and a dichotomous key to all known species of Exsudoporus worldwide is presented.

This study revises the genus Cyanoboletus (Boletaceae) in the Mediterranean Basin, integrating single-locus and multi-locus phylogenetic analyses (ITS, LSU, tef1-α, and rpb2), morphological characterisation, ecology, and arsenic accumulation in basidiomes. Morphological descriptions (including a new form, Cyanoboletus mediterraneensis f. pallidus), comprehensive sampling, type studies, biogeography, macro- and microphotographs, an identification key, and a historical overview of the nomenclatural issues surrounding C. pulverulentus, C. poikilochromus, and C. mediterraneensis are given. An epitype collection is designated for C. pulverulentus. A new method to measure spore suprahilar depression has been proposed, which allowed more clear morphological separation between C. mediterraneensis and C. pulverulentus. This method may prove useful for species delimitation in other fungal groups that have asymmetric basidiospores. Additionally, we generated a new ITS sequence of the C. sinopulverulentus holotype and inferred its conspecificity with the later described C. flavocontextus. Furthermore, notes on the taxonomy of Boletus gabretae are presented, and its placement in the genus Neoboletus is suggested. Cyanoboletus is confirmed as a strongly supported generic clade encompassing 21 monophyletic species-level clades, 14 of which represent known species, and seven are undescribed taxa. The synonymy of Cupreoboletus with Cyanoboletus is also verified. This publication provides the tools to delimit Cyanoboletus species that have important conservation value, which can be used by conservationists, ecologists, and citizen scientists. It also highlights species-specific arsenic hyperaccumulation in C. pulverulentus, contributing to a better understanding of fungal metal uptake. Our study indicates that within Cyanoboletus, only C. pulverulentus demonstrates this characteristic and is the only known member of Boletales that possesses a high arsenic accumulation ability.