Taxonomy and systematics of <i>Hyaloscyphaceae</i> and <i>Arachnopezizaceae</i>

The circumscription and composition of the <i>Hyaloscyphaceae</i> are controversial and based on poorly sampled or unsupported phylogenies. The generic limits within the hyaloscyphoid fungi are also very poorly understood. To address this issue, a robust five-gene Bayesian phylogeny (LSU, <i>RPB1</i>, <i>RPB2</i>, <i>TEF-1α</i>, mtSSU; 5521 bp) with a focus on the core group of <i>Hyaloscyphaceae</i> and <i>Arachnopezizaceae</i> is presented here, with comparative morphological and histochemical characters. A wide representative sampling of <i>Hyaloscypha</i> supports it as monophyletic and shows <i>H. aureliella</i> (subgenus <i>Eupezizella</i>) to be a strongly supported sister taxon. Reinforced by distinguishing morphological features, <i>Eupezizella</i> is here recognised as a separate genus, comprising <i>E. aureliella</i>, <i>E. britannica</i>, <i>E. roseoguttata</i> and <i>E. nipponica</i> (previously treated in <i>Hyaloscypha</i>). In a sister group to the <i>Hyaloscypha</i>-<i>Eupezizella</i> clade a new genus, <i>Mimicoscypha</i>, is created for three seldom collected and poorly understood species, <i>M. lacrimiformis</i>, <i>M. mimica</i> (<i>nom. nov.</i>) and <i>M. paludosa</i>, previously treated in <i>Phialina</i>, <i>Hyaloscypha</i> and <i>Eriopezia</i>, respectively. The <i>Arachnopezizaceae</i> is polyphyletic, because <i>Arachnoscypha</i> forms a monophyletic group with <i>Polydesmia pruinosa</i>, distant to <i>Arachnopeziza</i> and <i>Eriopezia</i>; in addition, <i>Arachnopeziza variepilosa</i> represents an early diverging lineage in <i>Hyaloscyphaceae</i> s.str. The hyphae originating from the base of the apothecia in <i>Arachnoscypha</i> are considered anchoring hyphae (vs a subiculum) and <i>Arachnoscypha</i> is excluded from <i>Arachnopezizaceae</i>. A new genus, <i>Resinoscypha</i>, is established to accommodate <i>Arachnopeziza variepilosa</i> and <i>A. monoseptata</i>, originally described in <i>Protounguicularia. Mimicoscypha</i> and <i>Resinoscypha</i> are distinguished among hyaloscyphoid fungi by long tapering multiseptate hairs that are not dextrinoid or glassy, in combination with ectal excipulum cells with deep amyloid nodules. Unique to <i>Resinoscypha</i> is cyanophilous resinous content in the hairs concentrated at the apex and septa. Small intensely amyloid nodules in the hairs are furthermore characteristic for <i>Resinoscypha</i> and <i>Eupezizella</i>. To elucidate species limits and diversity in <i>Arachnopeziza</i>, mainly from Northern Europe, we applied genealogical concordance phylogenetic species recognition (GCPSR) using analyses of individual datasets (ITS, LSU, <i>RPB1</i>, <i>RPB2</i>, <i>TEF-1α</i>) and comparative morphology. Eight species were identified as highly supported and reciprocally monophyletic. Four of these are newly discovered species, with two formally described here, viz. <i>A. estonica</i> and <i>A. ptilidiophila</i>. In addition, <i>Belonium sphagnisedum</i>, which completely lacks prominent hairs, is here combined in <i>Arachnopeziza</i>, widening the concept of the genus. Numerous publicly available sequences named <i>A. aurata</i> represent <i>A. delicatula</i> and the confusion between these two species is clarified. An additional four singletons are considered to be distinct species, because they were genetically divergent from their sisters. A highly supported five-gene phylogeny of <i>Arachnopezizaceae</i> identified four major clades in <i>Arachnopeziza</i>, with <i>Eriopezia</i> as a sister group. Two of the clades include species with a strong connection to bryophytes; the third clade includes species growing on bulky woody substrates and with pigmented exudates on the hairs; and the fourth clade species with hyaline exudates growing on both bryophytes and hardwood. A morphological account is given of the composition of <i>Hyaloscyphaceae</i> and <i>Arachnopezizaceae</i>, including new observations on vital and histochemical characters. <b>Citation</b>: Kosonen T, Huhtinen S, Hansen K. 2021. Taxonomy and systematics of Hyaloscyphaceae and Arachnopezizaceae. Persoonia 46: 26-62. https://doi.org/10.3767/persoonia.2021.46.02.