Morphological and molecular re-assessment of European and Levantine species of the genus Hortiboletus (Boletaceae).

(the former species complex) is one of the most taxonomically critical and difficult genera for species identification in the family . Here, we provide a detailed morphological and molecular re-assessment of European and Levantine species of . A new species, , is described from Israel. It is sister to and associated with the evergreen oak and potentially also with . 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 , , , and are given. An epitype collection is designated for . A key is provided for identification of the European and Levantine taxa. In addition, we propose a novel taxonomic combination , which is conspecific with Boletus rubellus var. flammeus, based on the DNA barcoding and phylogenetic analysis of type material. is also shown to be conspecific with . A multilocus phylogenetic analysis of four markers (ITS, LSU, , and ) reveals that is a sister genus to . Using the Genealogical Concordance Phylogenetic Species Recognition method, at least 19 phylogenetic species and eight putative phylogenetic species of the genus 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 , but in the entire subfamily . Their identification and characterisation were based on Tandem Repeat Finder analysis and visual assessment of the ITS alignment.