A new genus and four new species in the /Psathyrella s.l. clade from China

Abstract Based on traditional morphological and phylogenetic analyses (ITS, LSU, tef-1α and β-tub) of psathyrelloid specimens collected from China, four new species are here described: Heteropsathyrella macrocystidia, Psathyrella amygdalinospora, P. piluliformoides, and P. truncatisporoides. H. macrocystidia forms a distinct lineage and groups together with Cystoagaricus, Kauffmania, and Typhrasa in the /Psathyrella s.l. clade, based on the Maximum Likelihood and Bayesian analyses. Thus, the monospecific genus Heteropsathyrella gen. nov. is introduced for the single species. Detailed descriptions, colour photos, and illustrations are presented in this paper.

As a part of the study of Chinese psathyrelloid species, four new species were discovered, during our investigations in temperate and subtropical regions of China from 2016-2019. Among them was a new species morphologically similar to Psathyrella but phylogenetically distinguished from it, and which formed a separate lineage. We recognize this new taxon as a new genus based on traditional morphological and phylogenetic analyses. In this paper, detailed information on the new taxa is presented.

Morphological studies
Macroscopic characteristics of fresh specimens were recorded. Colour codes followed Kornerup and Wanscher (1978). Thirty basidiospores, cystidia, and basidia were measured under a microscope in water and 5% aqueous KOH for each specimen. The measurements and Q values are given as (a)b-c(d), in which "a" is the lowest value, "b-c" covers a minimum of 90% of the values and "d" is the highest value. "Q" stands for the ratio of length to width of a spore (Bas 1969;Yu et al. 2020). Photographs of some microscopic characteristics are shown in Suppl. material 1: Figure S1. Specimens were deposited in the Herbarium of Mycology, Jilin Agricultural University (HMJAU).

Phylogenetic results
The aligned complete dataset consisted of 54 taxa and 2606 characters (ITS 711 bp, LSU 829 bp, Tef 1 st 69 bp, Tef 2 nd 136 bp, Tef 3 rd 497 bp, Tub 1 st 125 bp, and Tub 2 nd 239 bp). Due to the different number of models supported by Mrbayes and IQtree, the best models are calculated separately, and the results are as follows: the best models for Bayesian analysis were GTR+I+G for the ITS, LSU, Tef 3 rd , and Tub 2 nd , HKY+I for Tef 1 st , SYM+G for Tef 2 nd , and SYM+I+G for Tub 1 st ; the best models for ML analysis were TIM2+F+I+G4 for the ITS and LSU, TNe+FQ+I for Tef 1 st and Tef 2 nd , TIM2+F+G4 for Tef 3 rd , TIMe+FQ+G4 for Tub 1 st , and HKY+F+G4 for Tub 2 nd .
For Bayes analysis, the average standard deviation of split frequencies less than 0.01 after 610 thousand generations. The Bayesian inference (BI) and ML bootstrap proportions are shown in the Bayesian tree (Fig. 1). In addition, the ML tree is shown in Suppl. material 2: Figure S2. The phylogenetic tree analyses recovered 8 major supported clades    Diagnosis. Differs from Psathyrella epimyces by saprophytic and abundant pseudoparaphyses.
Habit and habitat. Scattered on mossy rotten wood in mixed forests of larch and birch.
Other specimens examined. Etymology. Referring to the spore shape. Diagnosis. Differs from P. obtusata by its spores, ovoid in front view, amygdaliform in profile and dark brown and gradually becoming black-brown in 5% KOH.

Discussion
The species in the family Psathyrellaceae can be roughly divided into two types by macromorphology: psathyrelloid and coprinoid. Heteropsathyrella is macromorphologically similar to Psathyrella s.s. but phylogenetically and micromorphologically distinguished from it, differing in the special pileipellis which composed of utriform to subglobose cells covered by a 1 cell deep layer of periclinal hyphae and abundant pseudoparaphyses. There are no other genera in this family, like Heteropsathyrella, that match the characteristics of psathyrelloid basidiomata, lamellae adnexed, basidia monomorphic, pseudoparaphyses abundant and pileipellis composed of a cellular subpellis below a hyphal suprapellis covered by scattered and irregular deposits, which dissolve in 5% KOH. Based on the study of this family (Smith 1972;Kits van Waveren 1985;Nagy et al. 2013;Örstadius et al. 2015), a detailed feature comparison between Heteropsathyrella and related genera are shown in Table 2. The type species, H. macrocystidia, is characterized by stout basidiomata, large pleurocystidia up to 80 μm long, and the generic characters above cited. Thus, this taxon is obviously unique and distinguished from all known species. In the case of not comparing the pileipellis and pseudoparaphyses, few species have the aspect of H. macrocystidia: P. epimyces (Peck) A.H. Sm. has stout basidiomata, and large pleurocystidia up to 70 μm long, but parasitic on Coprinus-or Coprinopsis-species (Smith 1972); P. parvifibrillosa A.H. Sm. and P. lauricola A.H. Sm. & Hesler has large pleurocystidia up to 70 μm long, but basidiomata small, and the shape of pleurocystidia are fusoid and utriform without long stipe at the base, respectively (Smith 1972).
For several of the already formally described and circumscribed clades within Psathyrella, phylogenetic analyses suggest that they include a morphologically heterogeneous assemblage of species, and morphological characterization is difficult (Örstadius et al. 2015). The boundaries between species in the /noli-tangere clade are difficult to characterize; these taxa share the characteristics of spores less than 10 μm long, and utriform, fusiform, lageniform or transition-type pleurocystidia present at the same time. The new species P. amygdalinospora forms an independent lineage and differs from the others in spores being ovoid in front view, amygdaliform in profile, and germ pore being absent. Macromorphologically, this species is similar to P. obtusata (Pers.) A.H. Sm. and P. fulvescens (Romagn.) M.M. Moser ex A.H. Sm, but the spores of P. obtusata are ellipsoid to oblong-ellipsoid and pale yellow in 5% KOH (Örstadius and Knudsen 2012), while P. fulvescens has an obvious germ pore (Smith 1972).
P. amygdalinospora can be classified into section Pennatae in Kits van Waveren's classification system (Kits van Waveren 1985) and in subsection Limicolae in Smith's  (Smith 1972). The closest related species can be separated as follows: the pleurocystidia of P. pennata (Fr.) A. Pearson & Dennis are fusoid-ventricose with an acute apex and thickened wall (Kits van Waveren 1985); the spores of P. borealis A.H. Sm. are ellipsoid and have an obvious germ pore (Smith 1972). The species in the /pygmaea clade share abundant cheilocystidia and utriform pleurocystidia. The new species P. truncatisporoides forms a distinct lineage and groups together with P. rybergii Örstadius & E. Larss. in this clade. The closely related P. rybergii differs in having spore lengths of 8.5-9.5 μm. Macromorphologically, there are hardly any other species that match the characteristics of P. truncatisporoides and they can be separated as follows: P. rubiginosa A. H. Sm. has subdistant lamellae and a very inconspicuous germ pores (Smith 1972); the pleurocystidia of P. noli-tangere (Fr.) A. Pearson & Dennis are narrowly utriform to lageniform and rarely forked (Kits van Waveren 1985); the spores of P. elliptispora A.H. Sm. are 8.0-11.0 μm long (Smith 1972).
The morphological boundary of the /piluliformis clade is basically the same as that of section Hydrophilae delineated by Kits van Waveren (1985). The new species P. piluliformoides forms a distinct lineage in this clade and can be separated by having an obvious ring. The closely related P. oboensis also exhibits very closed lamellae but differs in absence of a ring and clavate-mucronate pleurocystidia. Few species have been described resembling P. piluliformoides and they can be separated as follows: P. piluliformis (Bull.) P.D. Orton has no ring and without yellow amorphous incrustation at the apex of pleurocystidia (Örstadius and Knudsen 2012); P. laevissima (Romagn.) Singer has mucronate pleurocystidia (Kits van Waveren 1985).