(3014) Proposal to conserve the name Clitocybe (Basidiomycota) with a conserved type

Abstract

(3014) Clitocybe (Fr.) Staude, Schwämme Mitteldeutschl.: xxviii, 122. 1857 ≡ Agaricus “trib.” Clitocybe Fr., Syst. Mycol. 1: 9, 78. 1 Jan 1821, nom. sanct. (Fries, ibid.), nom. cons. prop.

Typus: Agaricus phyllophilus Pers., nom. sanct. (C. phyllophila (Pers.) P. Kumm.), typ. cons. prop.

Clitocybe (Fr.) Staude (Schwämme Mitteldeutschl.: xxviii, 122. 1857) is a genus of the family Clitocybaceae Vizzini & al. (in Index Fungorum 462: 1. 2020), characterized by the clitocyboid basidiome typically with a depressed pileus and decurrent lamellae. The genus currently encompasses approximately 500 species, according to the Index Fungorum database (www.indexfungorum.org, accessed on 1 Oct 2023). A substantial proportion of these species is included in specific monographs of Harmaja (in Karstenia 10: 5–168. 1969) and Bigelow (N. Amer. Sp. Clitocybe 1. 1982; 2. 1985). The genus exhibits a wide global distribution, and has also been extensively documented in various comprehensive monographs, journals or field guides from Africa (e.g., Pegler in Persoonia 4: 73–124. 1966), Asia (e.g., Li & al., Atlas Chinese Macrofungal Resources. 2015), Europe (e.g., Bas & al., Fl. Agaricina Neerl. 3. 1995), North America (e.g., Phillips, Mushrooms Other Fungi N. Amer. 2005), South America (e.g., Dennis, Fungus Fl. Venezuela. 1970), Australia (Grgurinovic, Larger Fungi S. Australia. 1997), and New Zealand (e.g., Cooper, New Zealand Clitocybaceae. 2016). The genus has been demonstrated to serve as a valuable reservoir of edible and medicinal resources (Wu & al. in Fungal Diversity 98: 1–76. 2019). Meanwhile, the genus has also been found to contain numerous muscarine-producing poisonous mushrooms (Genest & al. in J. Pharmacol. Sci. 57: 331–333. 1968; He & al. in Fungal Diversity 123: 1–47. 2023).

Recent multi-locus phylogenetic and phylogenomic analyses of Clitocybaceae, conducted by He & al. (l.c.), revealed the presence of six generic clades based on comprehensive assessments of genetic distance and divergence time. In the phylograms, the genera Dendrocollybia, Lepista s.str., Pseudolyophyllum, and Singerocybe each formed a distinct clade, whereas Clitocybe fell into the remaining two generic clades. The first clade exhibited robustness, encompassing the majority of traditional Clitocybe, Collybia, and Lepista species, while the second clade comprised only a few Clitocybe species.

The first generic clade can be divided into four subclades, including species previously classified under (1) Clitocybe sect. Candicantes (Quél.) Konrad & Maubl. (Icon. Select. Fung. 10: 331. 1937), C. sect. Odorae H.E. Bigelow (l.c. 1982: 148), and Collybia s.str. (Fr.) Staude (l.c.), (2) Lepista sect. Nuda Harmaja (in Karstenia 18: 49–54. 1978), (3) Clitocybe sect. Fragrans (Harmaja) Singer (Agaricales Modern Taxon., ed. 4: 247. 1986), and (4) the Lepista irina (Fr.) H.E. Bigelow complex.

Unfortunately, what was believed to be the first designated type of Clitocybe, C. nebularis (Batsch) P. Kumm., is positioned within the second generic clade, alongside only two other species, C. tomentosa Z.M. He & Zhu L. Yang and C. epixyla Z.M. He & Zhu L. Yang, leading to He & al. (l.c.) adopting Collybia for the first clade and restricting Clitocybe to the second very small clade. The initial designation of this type was proposed by Earle (in Bull. New York Bot. Gard. 5: 384. 1909) but, as Earle followed the American Code (McNeill & al. in Taxon 65: 1448. 2016), his type selections are superseded unless previously affirmed (Art. 10.5 of the ICN, Turland & al. in Regnum Veg. 159. 2018); the next typification of Clitocybe is therefore critical. It has been assumed that this was by Donk (in Bull. Jard. Bot. Buitenzorg, ser. 3, 18: 321–322. 1949), as, for example in Index nominum genericorum (Farr & al. in Regnum Veg. 100. 1979), who apparently affirmed Earle's selection of C. nebularis and this type is currently widely accepted among contemporary scholars (e.g., Harmaja in Ann. Bot. Fenn. 40: 213–218. 2003; Ammirati & al. in Mycoscience 48: 282–289. 2007; Vizzini & al. in Fungal Diversity 42: 97–105. 2010; Alvarado & al. in Mycologia 107: 123–136. 2015; Cooper, l.c.: 1–9). However, it has been overlooked that Clements & Shear (Gen. Fung., ed. 2: 348. 1931) designated C. infundibuliformis (Schaeff.) Quél. (in Mém. Soc. Émul. Montbéliard, sér. 2, 5: 88. 1872) as type thus superseding Earle's selection. Clements & Shear actually wrote: “C. infundibulis (Schaeff.) Fr.”, but this is evidently a correctable error for Quélet's name, as the only similar epithet used by Fries is Agaricus infundibulum Leyss. that Fries included, not in his “tribus” Clitocybe, but in A. “trib.” Omphalia. The basionym of C. infundibuliformis is A. infundibuliformis Schaeff. (Fung. Bavar. Palat. Nasc. 4: 49. 1774) that Fries (Syst. Mycol. 1: 81. 1821) included as a synonym of one of his species of A. “trib.” Clitocybe (A. flaccidus) and so is eligible for type selection. Fries later (l.c. Index: 25. 1832) associated A. infundibuliformis with A. gibbus Pers. Bigelow (l.c. 1982: 48) and Singer (l.c. 1986: 242) also thought that A. gibbus and A. infundibuliformis were conspecific. Since no original material of A. infundibuliformis is known to exist, we have referred to the description in the protologue and the illustration by Schaeffer (l.c. 3: t. CCXII. 1770). From these A. infundibuliformis appears to exhibit a rufous, tan to white, 6–8 cm wide, infundibuliform pileus, clearly indicating its classification within the genus Infundibulicybe (incertae sedis, Tricholomatineae) (Harmaja, l.c. 2003: 213–218; He & Yang in Mycologia 115: 693–713. 2023). However, this genus is only distantly related to Clitocybaceae (He & Yang in Mycokeys 79: 129–148. 2021; He & Yang in Mycol. Progr. 21: 26. 2022).

The genera Collybia and Clitocybe both originated from Staude (l.c.). The type of Collybia, C. tuberosa (Bull.) P. Kumm., was found to be nested within the first generic clade, leading He & al. (l.c.) to reluctantly classify this clade as Collybia. The situation appears discouraging when comparing the species numbers of the two generic clades. The first clade (called Collybia by He & al.) contains only the three species that are currently recognized in Collybia (viz. C. cirrhata, C. cookei, and C. tuberosa [type]), the hundreds once included in the genus having been transferred to other genera such as Dendrocollybia, Gymnopus, and Rhodocollybia (Antonín & al. in Mycotaxon 63: 359–368. 1997; Hughes & al. in Mycol. Res. 105: 164–172. 2001), but it would include hundreds of previous Clitocybe species or other taxa once placed under Clitocybe; whereas the second clade (erroneously named Clitocybe in He & al., l.c.) comprises only three above-mentioned described species, including C. nebularis that was thought by He & al. to be the type.

The current type of Clitocybe, Agaricus infundibuliformis, belongs to the recently established genus Infundibulicybe Harmaja (l.c. 2003: 215) that is unrelated to Clitocybaceae (He & Yang, l.c. 2022). Infundibulicybe is typified by A. gibbus to which A. infundibuliformis has commonly been linked, and it is undesirable to have to apply Clitocybe to Infundibulicybe. In order to maintain nomenclatural stability within Clitocybaceae and minimize potential name changes resulting from the phylogeny recovered by He & al. (l.c.), we hereby propose the selection of Clitocybe phyllophila (Pers.) P. Kumm. (≡ Collybia phyllophila (Pers.) Z.M. He & Zhu L. Yang) as a conserved type for Clitocybe. This proposal is based on several reasons: (1) this species conforms well to the characteristics of the conventional interpretation of Clitocybe, and is recorded within the “tribe Clitocybe” as stated in the protologue of Fries (l.c. 1821: 83); (2) it is present in the major and most species-rich subgenus of the genus referred to as Collybia for the present; (3) it produces the typical toxin muscarine, like other poisonous clitocybes; and (4) it has a large basidiome, similar to that of previously suggested lectotypes of Clitocybe (Agaricus nebularis and A. infundibuliformis), and is a common and widely distributed species accessible for scientific examination.

The generic type change also presents several significant advantages: (1) the majority of the species described within this genus would remain classified under Clitocybe, thereby avoiding hundreds of taxonomic combinations; (2) most of the traditional Lepista species fall within that generic clade, and their combinations with this genus name already exist, as Bigelow (in Brittonia 21: 144–177. 1965; l.c. 1982) treated Lepista as a section of Clitocybe; and (3) the phylogeny would also clearly delineate the generic boundary between Clitocybe in the new sense and Lepista s.str., ensuring that taxonomic literature and synonyms of Clitocybe remain unaffected.

The sole disadvantage of this proposal lies in its inevitable repercussion on a few species names in extensive use and the final extinction of Collybia. To the best of our knowledge, Collybia and Clitocybe have always been recognized as distinct genera and have not been taxonomically combined since their publication in 1857. Considering the current species numbers of the two genera, the name Clitocybe should be given precedence over the name Collybia. To establish this unequivocally, as provided in Art. 11.5, we publish here the new combination Clitocybe tuberosa (Bull.) Z.M. He & Zhu L. Yang, comb. nov. ≡ Agaricus tuberosus Bull. (Herb. France 6: t. 256. 1785–Feb 1786), nom. sanct. (Fries, Syst. Mycol. 1: 133. 1821) ≡ Collybia tuberosa (Bull.) P. Kumm. [Mycobank: 852416]. Collybia is conserved against Gymnopus (Pers.) Gray (Nat. Arr. Brit. Pl. 1: 604. 1821) (App. III B. Fungi in Wiersema & al., ICN Appendices I–VII, https://naturalhistory2.si.edu/botany/codes-proposals/), but the type of Gymnopus (G. purus (Pers.) Gray) is currently treated as Mycena pura (Pers.) P. Kumm. in the Myceaceae, belonging to a different suborder of the Agaricales from Clitocybaceae. Gymnopus does not, therefore, threaten Clitocybe and the latter need not be conserved against it.

The necessary revisions are (1) to transfer the remaining three species of previous Collybia s.str. aforementioned, along with 17 newly discovered Chinese species that have recently been classified under Collybia by He & al. (l.c.), to Clitocybe, and (2) to establish a new genus for C. nebularis and its two allies. Accordingly, the transfer will entail a significantly reduced number of new combinations compared to the several hundred combinations, including the adoption of Clitocybe for the some 30 species of the only distantly related Infundibulicybe, required if the type of Clitocybe were not changed with the new type conserved, as proposed.