A new checklist of the bryophytes of Britain and Ireland, 2020

1 Bell et al. (Citation2013) showed European accessions of ‘Sphaerocarpos texanus’ to be clearly distinct from the American and the latter is thus excluded from Europe. Sphaerocarpos europaeus is the oldest name based on a European specimen.

2 Molecular studies have shown Preissia to be deeply nested within Marchantia (Long et al. Citation2016).

3 Rubasinghe et al. (Citation2011) demonstrated that Athalamia Falc. and Clevea, previously treated as synonyms, should be recognised as distinct genera.

4 The name Riccia beyrichiana is ascribed to Hampe by Hodgetts et al. (Citation2020). However, the description was published by Lehmann (Citation1838). Although Lehmann ascribed the name to Hampe, he did not unequivocally associate Hampe with the validating description. The citation ‘Hampe ex Lehm.’ is therefore appropriate (ICN Art. 46.2, 46.5).

5 Although Pellia epiphylla subsp. borealis is recognised in Hodgetts et al. (Citation2020), we continue to follow Grolle (Citation1983) and Grolle and Long (Citation2000) in regarding it as a synonym of P. epiphylla.

6 Molecular studies by Schütz et al. (Citation2016) demonstrated clear molecular differences between Pellia endiviifolia and the other species of Pellia, but whether it is segregated in a different genus is largely a matter of taxonomic ideology. The genus remains monophyletic if P. endiviifolia is included, and we prefer to retain it in its broad traditional definition.

7 Although previously treated as a synonym of Fossombronia caespitiformis subsp. multispira (Schiffn.) J.R.Bray & Cargill by Bray (Citation2001), more evidence is needed to refute the status of F. husnotii as a distinct species, and to verify the taxonomic value of elater structure and rhizoid colour.

8 Bray (Citation2001) referred specimens of Fossombronia incurva from Yorkshire and Perthshire to F. fleischeri Ostervald. However, recent study of herbarium specimens suggests that only a single taxon occurs in Britain and Ireland, and it is doubtful whether F. fleischeri can be maintained as a separate species, at least in these islands.

9 The name Petalophyllum is ascribed to Nees & Gottsche by Hodgetts et al. (Citation2020) but the description of the genus was published by Lehmann (Citation1844). Although Lehmann attributed the name to ‘Nees ab Esenb. et Gottsche Ms.’, he did not unequivocally associate Nees & Gottsche with the validating description (ICN Art. 46.2, 46.5). In the same publication Lehmann made the combination Petalophyllum ralfsii and ascribed it to Nees & Gottsche. In the absence of a statement that Nees & Gottsche contributed to the publication of Lehmann's paper, the citation ‘Nees & Gottsche. ex Lehm.’ is appropriate (ICN Art. 46.2, 46.5).

10 The affinities of European Metzgeria consanguinea, previously known as M. temperata, need to be clarified. Unpublished molecular studies show that the European populations are closer to Metzgeria violacea than to the Japanese Metzgeria temperata (see Köckinger Citation2017).

11 Hodgetts et al. (Citation2020) attribute the combination Metzgeria furcata var. ulvula to Pavletić. In the protologue of this taxon, Nees von Esenbeck (Citation1838) used letters of the Greek alphabet to list infraspecific taxa without an explicit designation of rank. However, it is clear that his taxa were at the rank of forma (thus on a subsequent page (493) he used the wording ‘Die Form ζ Ulvula’). Gottsche et al. (Citation1844–Citation1847) used the same method of listing infraspecific taxa, but it is clear from their text that they regarded them as varieties (e.g. they use the wording ‘Var. β 1 ** campylotricha’ on p. 504 for a different taxon under M. furcata). Thus it can be concluded that they were the first authors to treat var. ulvula at varietal rank.

12 Hodgetts et al. (Citation2020) attribute the name Radula voluta to Taylor. However, the description was published by Gottsche et al. (Citation1844–Citation1847). Although Gottsche et al. ascribed the name to Taylor, they did not unequivocally associate Taylor with the validating description (ICN Art. 46.2, 46.5), and our citation therefore follows Grolle and Long (Citation2000).

13 Frullania microphylla var. deciduifolia is not recognised by Sim-Sim (Citation1999) as ‘all specimens from Portugal or Madeira have deciduous leaves’, a treatment followed by both Söderström et al. (Citation2016) and Hodgetts et al. (Citation2020). However, it is retained here pending new evidence.

14 Hodgetts et al. (Citation2020) attribute the combination Cololejeunea minutissima to Schiffner, but this was published in 1893 (in Engler and Prantl Citation1887–Citation1915). The combination was made in the previous year by Stephani (Citation1892) (see Söderström et al. Citation2015).

15 There is still doubt about the synonymy of Lejeunea holtii with L. eckloniana, and further studies are needed.

16 Blepharostoma trichophyllum subsp. brevirete was found in Scotland (Ben Alder) in 2014 (Ellis et al. Citation2017).

17 Sun and He (Citation2019) recently proposed synonymising Herbertus borealis, H. norenus and H. stramineus with H. aduncus (in which they include H. hutchinsiae). While undoubtedly closely related, the small genetic differences between these taxa result in very clear morphological differences, and in the field the species (which sometimes grow in close proximity) are easily distinguished by morphology, ecology and distribution. We therefore follow Hodgetts et al. (Citation2020) in rejecting the synonymies.

18 Herbertus norenus was described from Norway and Scotland by Bell et al. (Citation2012).

19 Tricholepidozia was elevated to a separate genus by Cooper et al. (Citation2013), and Telaranea murphyae was shown to be synonymous with Tricholepidozia tetradactyla by Villarreal et al. (Citation2014).

20 Tricholepidozia lindenbergii (var. lindenbergii) was reported as new to Britain (and the Northern Hemisphere) by Blackstock et al. (Citation2019).

21 We continue to treat Lophocolea bidentata in a broad sense, although Lophocolea coadunata, the taxon previously referred to in Britain and Ireland as L. cuspidata (Nees) Limpr., is listed as distinct by Hodgetts et al. (Citation2020).

22 Lophocolea muricata has been found recently by D. A. Callaghan as an introduced species on tree-ferns in Somerset. A report of its occurrence is in preparation (Ellis, Ah-Peng, et al. Citation2021).

23 Many recent publications (e.g. Köckinger Citation2017) do not recognise any varieties of the two species of Chiloscyphus. However, they are listed by Stotler and Crandall-Stotler (Citation2017) and Hodgetts et al. (Citation2020). They have not been recorded consistently and we choose to treat the two species of Chiloscyphus broadly pending further work.

24 Hodgetts et al. (Citation2020) ascribe the basionym of Chiloscyphus pallescens to Ehrhart. However, the basionym Jungermannia pallescens was published by Hoffmann (Citation1796) with reference to an Ehrhart exsiccate and he did not unequivocally associate Ehrhart with the validating description (ICN Art. 46.2, 46.5). In addition, the combination C. pallescens var. fragilis was not effectively made by Müller (Citation1942), who treated it at species level. It was later validated by Schuster (Citation1949) (Tropicos database).

25 The name Plagiochila heterophylla is ascribed to Lindenberg by Hodgetts et al. (Citation2020) but it was published by Lehmann (Citation1844). Although Lehmann ascribed the name to Lindenberg, he did not unequivocally associate Lindenberg with the validating description. The citation ‘Lindenb. ex Lehm.’ is therefore appropriate (ICN Art. 46.2, 46.5).

26 Váňa et al. (Citation2012) and others showed that Leiocolea and Mesoptychia should be regarded within a single genus, and Mesoptychia is the older name.

27 Leiocolea rutheana var. laxa was shown to be more closely related to L. gillmanii by Bell et al. (Citation2013), and the new combination in Mesoptychia was made in Hodgetts et al. (Citation2020).

28 Konstantinova and Vilnet (Citation2016), and later Mamontov et al. (Citation2018), showed that Jungermannia exsertifolia subsp. cordifolia deserves specific status, as was previously proposed by Schljakov (Citation1981).

29 Endogemma, known for its production of endogenous gemmae, was established on the basis of molecular evidence that confirmed its isolation from other taxa in Jungermannia and Solenostoma (Vilnet et al. Citation2011). Although ascribed solely to Konstantinova by Hodgetts et al. (Citation2020), the name of the genus is explicitly ascribed to Konstant., Vilnet & A.V.Troitsky in the protologue (Vilnet et al. Citation2011).

30 The species arrangement in Gymnomitrion and Marsupella has been altered in accordance with Váňa et al. (Citation2010).

31 See note under Gymnomitrion.

32 Marsupella emarginata var. pearsonii is listed as a synonym of M. emarginata in Hodgetts et al. (Citation2020), and there is no reason to dispute this.

33 Molecular work by Vilnet et al. (Citation2010) showed Marsupella emarginata and M. aquatica to be sister taxa, and we therefore follow Hodgetts et al. (Citation2020) in treating them as separate species.

34 Jamesoniella autumnalis was transferred to Syzygiella by Feldberg, Váňa, Hentschel, et al. (Citation2010).

35 The generic placement of Adelanthus decipiens was clarified by Feldberg, Váňa, Long, et al. (Citation2010).

36 Although there is some molecular evidence for subdividing Cephalozia, (e.g. Feldberg et al. Citation2016), the treatment in Hodgetts et al. (Citation2020) may be premature. We therefore adopt a broad concept of Cephalozia, which for the sake of consistency has to include Nowellia and Pleurocladula as well as Fuscocephaloziopsis.

37 Cephalozia bicuspidata subsp. lammersiana has a long history of debate on whether it is worth recognising at any level. The issue requires a molecular study before it can be resolved.

38 Some Scottish material of Cephalozia albescens is small and slender with nearly plane and deeply bilobed leaves, and could be referred to var. islandica (Nees) Kaal. However, Paton (Citation1999) considers that at least the Scottish plants are merely habitat forms.

39 Molecular and morphological studies by Gradstein and Ilkiu-Borges (Citation2015) showed that Cladopodiella is nested within Odontoschisma.

40 Hodgetts et al. (Citation2020) place Anastrophyllum hellerianum in Crossocalyx. Recent results from DNA barcoding and nuclear genomic datasets by D. Bell et al. (pers. comm.) indicate that it is close to (although clearly different from) the other members of the genus, and our majority view is to retain it in Anastrophyllum.

41 Recent results from DNA barcoding and nuclear genomic datasets by D. Bell et al. (pers. comm.) suggest a close relationship between Anastrophyllum saxicola, A. minutum, Barbilophozia kunzeana and Gymnocolea inflata, but until further work is done we follow the arrangement of Sphenolobus in Hodgetts et al. (Citation2020).

42 Hodgetts et al. (Citation2020) attribute the basionym of Sphenolobus minutus to Schreb. ex D.Crantz, but the author of the publication in which it appeared was David Cranz.

43 The taxonomic value of Gymnocolea inflata subsp. acutiloba is unclear. A detailed study is needed to clarify whether this is an extreme form of Gymnocolea inflata s.str.

44 Orthocaulis remains monophyletic if it includes Neoorthocaulis, according to the tree in De Roo et al. (Citation2007), and we therefore regard the segregation of Neoorthocaulis as superfluous.

45 Jamesoniella undulifolia was transferred to Biantheridion by Konstantinova and Vilnet (Citation2009).

46 The evidence for placing Barbilophozia quadriloba in the new genus Schljakovianthus Konstant. & Vilnet is equivocal, and recent results from DNA barcoding and nuclear genomic datasets by D. Bell et al. (pers. comm.) suggest a close relationship with Anastrepta orcadensis; it is therefore retained in Barbilophozia until further information is available.

47 The evidence for placing Barbilophozia kunzeana in the new genus Schljakovia Konstant. & Vilnet is equivocal, and recent results from DNA barcoding and nuclear genomic datasets by D. Bell et al. (pers. comm.) suggest a close relationship with Gymnocolea inflata; we therefore retain it in Barbilophozia until further information is available.

48 De Roo et al. (Citation2007) presented evidence to show that Lophozia bicrenata should be placed in Isopaches.

49 The placing of Protolophozia, Oleolophozia and Obtusifolium in Cephaloziellaceae is counter-intuitive. They are placed in a broadly-conceived Cephaloziellaceae by Hodgetts et al. (Citation2020), as they have been excluded from other families on the basis of molecular studies, and seem closer to Cephaloziellaceae than anything else. However, more work needs to be done.

50 Schuster (Citation1980) credited the combination of Cephaloziella spinigera to Jørgensen in 1934, and this is followed by Hodgetts et al. (Citation2020). However, Warnstorf had effected the new combination in 1913 (Stotler and Crandall-Stotler Citation2017).

51 Hodgetts et al. (Citation2020) attribute the combination Cephaloziella rubella to Warnstorf (Citation1902), but it was made earlier by Schiffner (Citation1900).

52 Listed in Hodgetts et al. (Citation2020), the taxonomic value of Cephaloziella divaricata var. scabra is controversial. In Central Europe var. scabra intergrades with var. divaricata and is possibly only a morph of shady habitats (Köckinger Citation2017).

53 The spelling of the epithet massalongoi follows the Tropicos database, in accordance with ICN Art. 60.8 (the omission of a terminal vowel of a personal name is to be treated as a correctable orthographic error). Massalongo's name did not possess a well-established latinised form.

54 Lophozia herzogiana was transferred to Protolophozia by Váňa et al. (Citation2013).

55 Lophozia perssonii was transferred to Oleolophozia by Söderström et al. (Citation2010).

56 The molecular evidence for the distinctness of Lophozia obtusa is ambiguous, but it seems sufficiently different from Lophozia to return it to Obtusifolium, a genus coined by Arnell (Citation1956).

57 The genus Lophoziopsis was created by Konstantinova and Vilnet (Citation2009) and accepted by Hodgetts et al. Citation2020. However, according to the phylogenetic tree in Vilnet et al. (Citation2008), it is sister to Lophozia, but very closely related, and it is doubtful whether a new genus is necessary.

58 The Lophozia ventricosa/wenzelii complex is mired in confusion, and new morphological and molecular studies are needed to clarify it; see Hodgetts et al. (Citation2020) for more detailed notes.

59 Lophozia guttulata includes L. longiflora sensu Grolle and Long (Citation2000), Söderström et al. (Citation2002) and Damsholt (Citation2002), and is a plant of moist dead-wood habitats. This is the plant that occurs in Scotland and is described in Paton (Citation1999). Lophozia longiflora (Nees) Schiffn., listed separately in Hodgetts et al. (Citation2020), corresponds to the concept of Müller (Citation1954), Saukel (Citation1985), Meinunger and Schröder (Citation2007), Bakalin (Citation2016) and Köckinger (Citation2017), describing a species occurring mostly on peaty soil and in rocky habitats.

60 See note on L. ventricosa; the status of L. wenzelii in Britain and Ireland is still very uncertain.

61 Lophozia capitata was transferred to Heterogemma by Konstantinova and Vilnet (Citation2009), based on Vilnet et al. (Citation2008).

62 According to the phylogenetic trees in Vilnet et al. (Citation2010), Trilophozia and Tritomaria remain monophyletic when combined, and we choose to retain all the species in Tritomaria.

63 Subgenus Schistochilopsis was raised to genus level by Konstantinova and Vasiljev (Citation1994), and this has been generally accepted in modern literature (e.g. Söderström et al. Citation2016; Hodgetts et al. Citation2020).

64 The molecular analyses of Vilnet et al. (Citation2010, Citation2012) support the recognition of Saccobasis as a genus, with S. polita as its only British representative.

65 We agree with Hodgetts et al. (Citation2020, annotation 44) in regarding Withering's original spelling of the species epithet (‘ornithopoides’) as an orthographic error. However, a proposal to conserve the spelling ‘ornithopodioides’ has been rejected by the Nomenclature Committee for Bryophytes.

66 The name Scapania nimbosa is ascribed to Taylor by Hodgetts et al. (Citation2020) but it was published by Lehmann (Citation1857). Although Lehmann ascribed the name to Taylor, he did not unequivocally associate Taylor with the validating description. The citation ‘Taylor ex Lehm.’ is therefore appropriate (ICN Art. 46.2, 46.5).

67 Sphagnum centrale is widely recognised as a species distinct from S. palustre in Europe and North America. Karlin et al. (Citation2010) studied microsatellite alleles, which showed that eastern North American populations of Sphagnum centrale and S. palustre are genetically distinct. However, in a comparable study in Europe, Crespo Pardo et al. (Citation2016) found that, in contrast with eastern North American populations, there was genetic overlap between S. centrale and S. palustre in mixed populations. In Britain, where S. centrale is rare, some specimens have variable morphology, with ventrally exposed chlorocysts in some leaves and centrally placed chlorocysts in others. There is probably genetic overlap in Britain also, and accordingly S. centrale is accorded varietal rank.

68 Hassel et al. (Citation2018) distinguished two European species, Sphagnum medium and S. divinum, from the South American S. magellanicum. Both European species occur in Britain and Ireland (Hill Citation2020).

69 Hodgetts et al. (Citation2020) ascribe the combination Sphagnum teres to Ångström. However, although Hartman (Citation1861) ascribed the combination to Ångström there seems to be no evidence that Ångström made a special contribution to Hartman's Flora (ICN Art. 46.2, 46.5), and the citation ‘Ångstr. ex Hartm.’ is therefore appropriate.

70 Hodgetts et al. (Citation2020) ascribe the basionym of Sphagnum quinquefarium to Braithwaite. However, Braithwaite (Citation1878) ascribed the basionym S. acutifolium Schrad. var. quinquefarium to Lindberg without unequivocally associating him with the validating description (ICN Art. 46.2, 46.5). The citation ‘Lindb. ex Braithw.’ is therefore appropriate.

71 Shaw et al. (Citation2005) note that Sphagnum capillifolium and S. rubellum each contain a monophyletic core of populations and should be retained as separate species. Intermediates do sometimes occur but according to Cronberg (Citation1996) the hybrids show occasional misplaced alleles and signs of developmental instability.

72 Kyrkjeeide et al. (Citation2015) distinguished Sphagnum beothuk from S. fuscum and noted the presence of S. beothuk on the Isle of Skye. Hill (Citation2017) mapped their distributions in Britain and Ireland.

73 Hodgetts et al. (Citation2020) ascribe the combination Sphagnum platyphyllum to Warnstorf. However, when Warnstorf (Citation1884) raised S. platyphyllum to species status he ascribed the name to Sullivant. It is appropriate, therefore, to cite the authorship as ‘Sull. ex Warnst.’ (Art. 46.5).

74 Hodgetts et al. (Citation2020) ascribe the combination Sphagnum tenellum to Pers. ex Brid. However, Persoon was merely the finder and did not coin the name. Bridel (Citation1797) was emphatic that S. cymbifolium (Ehrh.) Hedw. var. tenellum Brid. was in no way (nullatenus) worthy of species rank. Bory de Saint-Vincent (Citation1804) made the combination at species rank.

75 Sphagnum cuspidatum var. viride occurs in Britain and Ireland but intergrades with var. cuspidatum and is not recognised here. According to Hanssen et al. (Citation2000) the two varieties are not reproductively isolated.

76 Sphagnum fallax var. brevifolium and var. isoviitae are listed by Hodgetts et al. (Citation2020) but intergrade too much with var. fallax to be recognised here. According to Stenøien and Såstad (Citation1999) a test of population differentiation showed no significant divergence between S. fallax and S. isoviitae Flatberg growing in sympatry. It is suggested by Hodgetts et al. (Citation2020) that the differences may be epigenetic.

77 Hodgetts et al. (Citation2020) ascribe the basionym of Sphagnum angustifolium to C.E.O.Jensen ex Russow. However, Jensen's epithet was not validly published prior to Russow's paper and it is not clear that he used it at subspecific rank. We follow the Tropicos database in attributing it to Russow alone (ICN Art 46.4).

78 Price and Ellis (Citation2018) investigated the confused history of the name Andreaea alpina and designated a lectotype for it. Their lectotype belongs to the species previously known as Andreaea obovata. Consequently a new name is needed for the plant widely known hitherto as A. alpina. The earliest available name is Andreaea hookeri.

79 The treatment of Atrichum flavisetum as a distinct species follows the European checklists of Hill et al. (Citation2006) and Hodgetts et al. (Citation2020). It has not been recorded recently in Britain, and some of the records require verification. However, the first British report (Vaizey Citation1888) is detailed and convincing.

80 Bell and Hyvönen (Citation2010) showed that Polytrichastrum longisetum should be returned to its traditional home in Polytrichum.

81 Bell and Hyvönen (Citation2010) showed that Polytrichastrum formosum should be returned to its traditional home in Polytrichum.

82 Encalypta pilifera has been reinstated in Britain at the rank of species following Blockeel (Citation2013a).

83 Entosthodon mouretii was reported from Pembrokeshire, new to Britain, by Bosanquet (Citation2012).

84 Hodgetts et al. (Citation2020) ascribe the combination Physcomitrium pyriforme to Bruch & Schimp. However, the combination was validated by Bridel (Citation1826–Citation1827) in the Index to volume 2 of his work.

85 Hodgetts et al. (Citation2020) ascribe the authorship of Gymnostomum sphaericum (basionym of Physcomitrium sphaericum) to C.F.Ludw. ex Schkuhr. We follow the Tropicos database in treating this as C.Ludw. (a different Ludwig) in Schkuhr. The combination in Physcomitrium was validated by Bridel (Citation1826–Citation1827) in the index to volume 2 of his work.

86 Physcomitrium readeri was reported (as Ephemerella readeri) from Yorkshire, new to Britain, by Hooper et al. (Citation2010). Medina et al. (Citation2019) transferred it to Physcomitrium, which was the genus used by Müller in the protologue, though only with a very brief and incomplete diagnosis.

87 Using molecular data Medina et al. (Citation2019) concluded that there is no justification for retaining Physcomitrella Bruch & Schimp. and Physcomitridium G.Roth (Ephemerella Müll.Hal.) as separate genera from Physcomitrium.

88 Using molecular data, Fedosov, Fedorova, Fedosov, et al. (Citation2016) showed that Ditrichum flexicaule and D. gracile stand apart from other Ditrichum species, and perhaps do not even belong in the Dicranales. They transferred these two species to a new genus Flexitrichum and family Flexitrichaceae.

89 Werner et al. (Citation2013) showed that Hymenoloma and Dicranoweisia are distinct genera. Fedosov, Fedorova, Troitsky, et al. (Citation2016) subsequently placed Hymenoloma in a separate family, the Hymenolomataceae.

90 Bonfim Santos and Stech (Citation2017) transferred Campylopus subporodictyon to Atractylocarpus Mitt. It is clear that it does not belong in Campylopus, and the results of Bonfim Santos and Stech as well as results from DNA barcoding and nuclear genomic datasets by D. Bell et al. (pers. comm.) place it in a clade with Dicranodontium. The relationships of Dicranodontium and Atractylocarpus merit further studies, incorporating D. asperulum and D. uncinatum, which were not sequenced by Bonfim Santos and Stech. In the meantime we prefer to include D. subporodictyon in Dicranodontium, where it had been placed until recently (Hill et al. Citation2006).

91 Although striking in its extreme forms, Campylopus atrovirens var. falcatus intergrades with var. atrovirens, and we follow Hodgetts et al. (Citation2020) in reducing it to synonymy.

92 The species epithet of Amphidium mougeotii should be attributed to both Bruch & Schimper, as it was published in 1838, long before Bruch's death in 1847.

93 Hodgetts et al. (Citation2020) note that Dichodontium palustre does not sit comfortably in that genus, and they place it in the monotypic genus Diobelonella Ochyra. Historically D. palustre was included in Dicranella, but results from DNA barcoding and nuclear genomic datasets by D. Bell et al. (pers. comm.) indicate that it is rather distantly related to the type species of that genus, D. heteromalla, and that Dicranella itself is paraphyletic in its current circumscription. Pending clarification of the relationships of D. palustre we prefer to retain it in Dichodontium.

94 Hodgetts et al. (Citation2020) ascribe the combination Dicranella schreberiana to Dixon, but in using this name Dixon (Citation1933) references Schimper. However, Schimper's name was actually D. schreberi, which is a separate name.

95 Crundwell and Nyholm (Citation1977) found that intermediates between Dicranella varia and D. howei occurred in Britain and Ireland. Bosanquet (Citation2010) and Holyoak (Citation2012) provisionally reported D. howei from Pembroke and Cornwall respectively, but with reservations. However, unequivocal material of D. howei certainly occurs in Britain and it is probably widespread there (Blockeel Citation2020).

96 Hodgetts et al. (Citation2020) ascribe the name Fissidens rufulus to Bruch and Schimp., but it was published in 1851, after Bruch's death in 1847.

97 We follow Hodgetts et al. (Citation2020) in treating Fissidens taxifolius var. pallidicaulis (= subsp. pallidicaulis (Mitt.) P.de la Varde) as a synonym of F. taxifolius. The two varieties intergrade completely.

98 Dicranoloma menziesii was reported from Kerry, new to Ireland, by Holyoak and Lockhart (Citation2009).

99 Dicranum spadiceum was reported from Scotland, new to Britain, by Rothero (Citation2014).

100 Hodgetts et al. (Citation2020) attribute the name Dicranum majus to Smith, but Turner (Citation1804) has priority by nine days (Sayre Citation1959).

101 Hodgetts et al. (Citation2020) attribute the name Dicranum fuscescens to Smith, but Turner (Citation1804) has priority by nine days (Sayre Citation1959).

102 Hedenäs (Citation2017) clarified the status of Oncophorus integerrimus and it was subsequently reported from Scotland, new to Britain, by Rothero (Citation2020a).

103 Hodgetts et al. (Citation2020) ascribe the genus Dicranoweisia to Milde. However, in describing the genus, Milde (Citation1869) attributed the name to Lindberg without unequivocally associating him with the validating description (ICN Art. 46.2, 46.5). The citation ‘Lindb. ex Milde’ is therefore appropriate.

104 Hodgetts et al. (Citation2020) ascribe the combination Dicranoweisia cirrata to Lindberg. However, although Milde (Citation1869) attributed the combination to Lindberg, there is no indication that Lindberg made a special contribution to the publication (ICN Art. 46.2, 46.5), and the citation ‘Lindb. ex Milde’ is therefore appropriate.

105 Arctoa anderssonii was reported in Sutherland, new to Britain, by Rothero (Citation2009).

106 Hodgetts et al. (Citation2020) ascribe the name Ditrichum zonatum at species level to Kindb., but the combination was made one year earlier by Lees (Citation1881).

107 Ditrichum pallidum was reported from Sussex, new to Britain, by Matcham and Blockeel (Citation2017).

108 Hodgetts et al. (Citation2020) ascribe the name Ditrichum subulatum to Hampe (Citation1867), but Hampe's name is a nomen nudum. The name was validly published by Hobkirk and Boswell (Citation1877).

109 Hodgetts et al. (Citation2020) ascribe the basionym of Ceratodon conicus to Hampe. However, the basionym Trichostomum conicum was published by Müller (Citation1849–Citation1851), who ascribed the name to Hampe ‘in litt.’, but did not unequivocally associate Hampe with the validating description (ICN Art. 46.2, 46.5). The citation ‘Hampe ex Müll.Hal.’ is therefore appropriate.

110 Hodgetts et al. (Citation2020) ascribe the name Cheilothela and the combination Cheilothela chloropus to Brotherus, but they were previously published by Lindberg (Citation1878).

111 Weissia × mittenii was last recorded in 1920. It is listed by Hodgetts et al. (Citation2020) but is currently considered to be a hybrid (Smith Citation2004; Callaghan Citation2019). It is therefore included in the present checklist in Table 2.

112 Werner, Ros, Guerra, et al. (Citation2004) provided evidence for the recognition of Weissia wimmeriana at species rank, although the morphological differences from W. controversa, primarily the paroicous inflorescence, are small.

113 Weissia brachycarpa var. brachycarpa and var. obliqua have long been recognised as distinct in Britain and Ireland, but rarely in continental Europe. As noted by Callaghan et al. (Citation2019), the morphological circumscription of taxa within Weissia is highly problematic. However, intermediates between these two varieties are rare in Britain and Ireland, and we therefore maintain them as distinct pending further study.

114 Callaghan et al. (Citation2019) showed that Weissia multicapsularis is a synonym of Phascum cuspidatum (Tortula acaulon). They created the name Weissia wilsonii for the moss previously known in Europe as W. multicapsularis.

115 Callaghan et al. (Citation2019) raised Weissia angustifolia to full species rank on the basis of molecular and morphological criteria.

116 Hodgetts et al. (Citation2020) ascribe the basionym of Pottiopsis caespitosa to Bridel. However in describing the basionym Weissia caespitosa, Bridel (Citation1826–Citation1827) cited Bruch's manuscript name without unequivocally associating him with the validating description (ICN Art. 46.2 46.5). The citation ‘Bruch ex Brid.’ is therefore appropriate.

117 Tortella limosella is known only from the type collection and is probably an aberrant form or genetic variant of another Tortella species, presumably T. flavovirens. Tortella flavovirens var. glareicola (T.A.Chr.) Crundw. & Nyholm is accepted by Hodgetts et al. (Citation2020), but in Britain and Ireland it is connected to var. flavovirens by numerous intermediates (Smith Citation2004; Holyoak Citation2012) and therefore we do not recognise it here. However, Bosanquet (Citation2010) notes the occurrence of a large-celled form of T. flavovirens in sand dunes in Pembrokeshire.

118 The studies of Werner et al. (Citation2005) and Grundmann et al. (Citation2006) showed that Pleurochaete squarrosa is nested in Tortella.

119 Köckinger and Hedenäs (Citation2017) showed that the name Tortella bambergeri has been mis-applied in recent years, and that plants reported under that name belong to two distinct species, for which the correct names are T. fasciculata and T. pseudofragilis. Ottley and Blockeel (Citation2019) revised British and Irish material and confirmed two British specimens of T. pseudofragilis from Scotland.

120 In their revision of material previously named Tortella bambergeri, Ottley and Blockeel (Citation2019) found that the great majority of specimens from Britain and Ireland belonged to T. fasciculata.

121 Alonso et al. (Citation2019) placed Oxystegus (including Trichostomum tenuirostre and related species) in Chionoloma.

122 In their molecular-based study of Oxystegus in Europe, Köckinger et al. (Citation2010) considered Chionoloma tenuirostre var. holtii (Oxystegus tenuirostris var. holtii) to merit recognition as a distinct variety. Blockeel (Citation2013b) accepted this conclusion but found some difficulty in applying the morphological criteria. Alonso et al. (Citation2019) included Oxystegus tenuirostris in Chionoloma, but used different morphological criteria, based on characters of the leaf margin, to separate var. holtii from var. tenuirostre. Further clarification of the morphological definition of var holtii is needed but we retain it as distinct for the time being.

123 Following Köckinger et al. (Citation2010), Blockeel (Citation2013b) recognised Oxystegus daldinianus as a British and Irish species. Alonso et al. (Citation2019) included it in Chionoloma and treated it as a synonym of C. cylindrotheca.

124 Chionoloma minus (Köckinger, O.Werner & Ros) M.Alonso, M.J.Cano & J.A.Jiménez was described (as Oxystegus minor Köckinger, O.Werner & Ros) by Köckinger et al. (Citation2010) from Austria, but they also assigned to it two specimens from Scotland. Blockeel (Citation2013b) was unable to find a clear morphological distinction between C. minus and C. hibernicum. Alonso et al. (Citation2019) also found overlap between these two species and they proposed to use a slight difference in the colour reaction of the leaf lamina in KOH as a means of separating them. Morphologically, C. minus may be a cryptic taxon. We consider that further evidence is needed to define it morphologically and justify its recognition in Britain and Ireland.

125 We follow Holyoak (Citation2010) in reducing Ephemerum sessile to subspecific rank under E. crassinervium.

126 We follow Holyoak (Citation2010) in treating Ephemerum hibernicum as a synonym of E. rutheanum Schimp. and reducing it to subspecific rank under E. crassinervium.

127 Hodgetts et al. (Citation2020) ascribe the name Ephemerum spinulosum to Bruch & Schimp. ex Schimp., but the same author may not appear in both parts of an ‘ex’ citation. Furthermore the Ephemerum spinulosum of Schimper (Citation1860, p. 6) lacks a diagnosis, and its putative basionym Phascum spinulosum Bruch & Schimp. ex Wilson (Citation1855, p. 27) also lacks one. Ephemerum spinulosum needs to be re-typified, but we do not attempt to do this here.

128 Ellis and Price (Citation2015) lectotypfied Ephemerum serratum and showed that it is the correct name for the plant with finely papillose spores; E. minutissimum is thus a synonym of it. The earliest name for the taxon with coarsely papillose spores is E. stoloniferum.

129 Leptodontium proliferum was reported from Lancashire, new to Britain and Europe, by Porley and Edwards (Citation2010). However Blockeel (Citation2017b) noted that plants of Leptodontium at a recently discovered site in Yorkshire showed characters intermediate between this species and L. gemmascens. The status of the English material of L. proliferum merits further study.

130 Using molecular data, Kučera et al. (Citation2013) showed that Streblotrichum should be reinstated to accommodate Barbula convoluta (and the European B. enderesii Garov.).

131 The varietal epithet of Barbula convoluta var. sardoa should be attributed to both Bruch & Schimper, as it was published in 1842, several years before Bruch's death in 1847.

132 Didymodon australasiae has been confirmed new to Britain, from molecular analysis, by Blockeel and Kučera (Citation2019).

133 Specimens formerly assigned to Didymodon acutus in Britain and Ireland mostly belong to D. icmadophilus. However, two specimens considered to belong to the true D. acutus have been confirmed from England (Blockeel and Kučera Citation2019).

134 Crossidium squamiferum was reported from the Isle of Wight, new to Britain, by Bosanquet (Citation2014).

135 Pterygoneurum papillosum was reported from southern England, new to Britain, by Blockeel and Ottley (Citation2015).

136 Tortula inermis was reported from Scotland, new to Britain, by Blockeel et al. (Citation2009).

137 Košnar and Kolář (Citation2009) found evidence from a cultivation experiment that the length of the hair-point in Tortula muralis is genetically determined. However, they also observed that there is morphological overlap between var. muralis and var. aestiva, and they noted that ‘the separation of these taxa based on costa excurrency alone seems to be rather arbitrary’. We believe that more evidence is needed to justify the recognition of var. aestiva and we do not recognise it here.

138 Ros et al. (Citation2008) showed that Tortula lindbergii is an earlier name for T. lanceola.

139 Ros et al. (Citation2008) showed that Tortula caucasica is an earlier name for T. modica. Hodgetts et al. (Citation2020) attribute the name to Brotherus. However Brotherus (Citation1892) ascribed the name to Lindberg. In acknowledging Lindberg's contribution to his paper, Brotherus does not include Tortula caucasica among the list of new species for which Lindberg had provided brief diagnostic notes on the packet. It was therefore one of the species for which Brotherus was obliged to write the description himself [‘force m'a été d'en faire moi-même toute la description’). The name is therefore correctly attributable to Brotherus, but the citation ‘Lind. ex Broth.’ is also allowable and appropriate (ICN Art. 46.5).

140 The inclusion of Phascum cuspidatum in Tortula follows Werner, Ros, Cano and Guerra (Citation2002, Citation2004).

141 Tortula acaulon var. schreberiana differs from var. acaulon only in the development of branched stems, and it is disregarded by many bryologists. There is no sharp morphological discontinuity between the two varieties. Pending evidence that it is genetically distinct we do not recognise it here.

142 Microbryum davallianum var. conicum was recognised in Britain and Ireland by Chamberlain (Citation1978, as Pottia starckeana subsp. conica), but Blockeel and Long (Citation1998) followed Ros et al. (Citation1996) in treating it as a synonym of M. davallianum. Conversely some European authors (e.g. Meinunger and Schröder Citation2007) consider it to be a well-defined species. Its status remains uncertain, and it has not been subject to molecular study, but we recognise it here because it has some morphological definition.

143 The inclusion of Leptophascum leptophyllum in Chenia follows Hedderson and Zander (Citation2008).

144 Syntrichia calcicola is widely recognised in Europe, and in a study based on Scandinavian material Hedenäs et al. (Citation2019) found molecular support for its status as a distinct species. Hitherto it has not been recognised by bryologists in Britain and Ireland because of the difficulty in separating it from S. ruralis, which is highly plastic in its morphology, especially in anthropogenic habitats. Further study of the status of S. calcicola in Britain and Ireland is needed, and for the time being we prefer to include it in a broadly defined S. ruralis.

145 Syntrichia ruralis var. epilosa was reported from Buckinghamshire and East Suffolk, new to Britain, by O’Leary and Fisk (Citation2019).

146 In a study based on Scandinavian material Hedenäs et al. (Citation2019) found molecular support for the recognition of Syntrichia ruraliformis as a distinct species.

147 Syntrichia montana var. calva was reported from Gloucestershire, new to Britain, by Martin (Citation2011). The varietal name calva was published in 1851, after Bruch's death in 1847, and therefore Bruch's name should not be cited in its authorship.

148 Hodgetts et al. (Citation2020) ascribe the basionym of Syntrichia papillosa to Wilson. However, in describing the basionym Tortula papillosa Spruce (Citation1845) ascribes the name to Wilson ‘MSS’ without unequivocally associating him with the validating description (ICN Art. 46.2, 46.5). The citation ‘Wilson ex Spruce’ is therefore appropriate. Spruce (Citation1867) was also the first author to make the combination in Syntrichia.

149 Fedosov et al. (Citation2017) separated Blindiadelphus at generic level from Seligeria on the basis of morphological and molecular evidence.

150 Hodgetts et al. (Citation2020) ascribe the combination Seligeria brevifolia to Lindberg. However, the paper in question was written by Lindberg and Arnell (Citation1890).

151 Hodgetts et al. (Citation2020) ascribe the combination Seligeria patula to I.Hagen. However, Hagen (Citation1906) refers to a paper by Lindberg (Citation1871) [‘1870’] in which Lindberg cites his own manuscript name ‘S. patula, Lindb. MS.’. The citation Lindb. ex I.Hagen is therefore appropriate.

152 Dickson's Bryum polyphyllum was validated in his index, published on 4 October 1801. The species epithet was also validated as Dicranum polyphyllum by Swartz (Citation1801), for which the date of publication is October to December 1801. As it seems likely that Dickson's publication preceded that of Swartz, we have cited him for the basionym.

153 Schistidium maritimum subsp. piliferum was reported from Shetland, new to Britain, by Hodgetts (Citation2010).

154 As noted in Hill et al. (Citation2008), S. elegantulum subsp. wilsonii H.H.Blom intergrades with subsp. elegantulum in Britain and Ireland, and consequently the subspecies are not recognised here.

155 Schistidium helveticum was reported from Scotland, new to Britain, by Blockeel et al. (Citation2009).

156 We follow Hodgetts et al. (Citation2020) in treating Grimmia sessitana as a synonym of G. reflexidens, but the taxonomy and nomenclature of these two taxa require further study.

157 Grimmia anomala was reported new to Britain and Ireland by Lönnell et al. (Citation2012).

158 Hodgetts et al. (Citation2020) ascribe the basionym of Racomitrium affine to F. Weber and D. Mohr. However Weber and Mohr (Citation1807) cite a Schleicher exsiccate of Trichostomum affine, and the citation ‘Schleich. ex F.Weber & D.Mohr’ is therefore appropriate.

159 In reviewing British and Irish material of Racomitrium heterostichum, Blockeel (Citation1991) treated R. obtusum as conspecific with R. heterostichum because of the difficulty in separating piliferous forms of R. obtusum from R. heterostichum s.str. However most specimens of R. obtusum are easily identified and therefore we follow Hodgetts et al. (Citation2020) in recognising it as a distinct species. Its detailed distribution in Britain and Ireland remains to be assessed, but Frisvoll (Citation1984) selected Dillenian material from Wales as the lectotype, and in his later monograph (Citation1988) he cited several confirmed records from Britain and Ireland.

160 Hedenäs (Citation1994) cited Hedwigia emodica Hampe ex Müll.Hal. as a synonym of H. ciliata var. leucophaea and the former name has been used for European plants by several subsequent authors, including Hodgetts et al. (Citation2020). However the type of H. emodica is from the Himalayan mountains, and Dalton et al. (Citation2013) noted that ‘according to Hedenäs (2011, pers. comm.), recent molecular work still in progress suggests that var. leucophaea may be a species in its own right distinct from H. emodica’. In view of this uncertainty, we retain the European name here, H. ciliata var. leucophaea.

161 Hedwigia striata was reinstated as a species in Britain and Ireland by Blockeel and Bosanquet (Citation2016) following the revision of Buchbender et al. (Citation2014). Whitehead and Fergusson's proposal to restore H. striata to the rank of species was made during a meeting of the Manchester Cryptogamic Society and subsequently reported anonymously in the journal The Naturalist (Anon Citation1879). It is uncertain whether the meeting report quotes the wording used by Whitehead and Fergusson, and therefore we prefer to use the ’ex’ citation here.

162 The treatment of Hedwigia integrifolia as a synonym of Braunia imberbis follows Dalton et al. (Citation2012). However according to De Luna (Citation2016) Braunia imberbis and some non-European species group together in a separate clade, suggesting that they may not belong in Braunia. Further research is needed.

163 Damayanti et al. (Citation2012) showed that the South American Bartramia stricta is not the same as the plant traditionally known by that name from Europe and the circum-Mediterranean region. They re-described the latter as B. rosamrosiae Damayanti, J.Muñoz, J.-P.Frahm & D.Quandt. Müller (Citation2014) subsequently synonymised B. rosamrosiae with B. aprica. As noted by Hodgetts et al. (Citation2020), it is not certain that this synonymy is correct, but we retain the name B. aprica pending further clarification.

164 Koponen and Isoviita (Citation2010) showed that the correct name for Philonotis arnellii is P. capillaris.

165 Hodgetts et al. (Citation2020) comment that ‘It also became apparent that morphology in Bryaceae often provides entirely misleading evidence of phylogeny …  Thus, morphological evolution in Bryaceae appears to be “decoupled” from phylogeny.’ For this reason, we have chosen to maintain Bryum as a single large genus, treating the genera of Hodgetts et al. (Citation2020) as subgenera or (Bryum and Imbribryum N.Pedersen) as sections.

166 Hodgetts et al. (Citation2020) ascribe Bryum marratii to Hook.f. & Wilson, but the Hooker in question was W.J. Hooker.

167 Bryum apiculatum was reported from England (Cornwall) by Holyoak (Citation2009). However subsequent studies have shown that the English plants are closely related to B. dichotomum and they are thought possibly to belong to an undescribed species (Hodgetts et al. Citation2020).

168 Bijlsma et al. (Citation2020) suggest that the European taxon previously known as Bryum microerythrocarpum Müll.Hal. & Kindb. is not identical with South American B. subapiculatum. However, they note that they ‘could not study the rhizoidal gemmae and other microscopic details’ of South American material. We therefore retain the name B. subapiculatum pending further clarification.

169 Hodgetts et al. (Citation2020) ascribe the combination Bryum intermedium to Blandow, but it was published earlier by Turton (Citation1806).

170 Hodgetts et al. (Citation2020) ascribe the name Bryum elegans to Nees. However, in describing this species, Bridel (Citation1826–Citation1827) attributed the name to Nees but did not unequivocally associate him with the validating description (ICN Art. 46.2, 46.5). The citation ‘Nees ex Brid.’ is therefore appropriate.

171 Hodgetts et al. ascribe the combination Bryum pseudotriquetrum var. bimum to Liljeblad, but Stafleu and Cowan (Citation1981) note that from page 257 onwards Liljeblad’s (Citation1816) Flora was edited by J. H. Wallman with the assistance of Swartz, Acharius, and Fries for the cryptogams.

172 Hodgetts et al. ascribe the generic name Mielichhoferia to Nees & Hornschuch. However, the genus is ascribed explicitly to Hornschuch alone in Nees von Esenbeck et al. (Citation1831).

173 We follow Smith (Citation2004) and Hill et al. (Citation2008) in treating Pohlia elongata var. acuminata as a synonym of P. elongata var. elongata.

174 Hodgetts et al. (Citation2020) ascribe the combination Pohlia proligera to Lindb. ex Broth. but Arnell (Citation1894) had previously made the combination, attributing the name to Lindberg. According to the Tropicos database Kindberg’s 1888 basionym Webera proligera is a nomen nudum, but was validly published by Breidler (Citation1891).

175 British and Irish plants of Pohlia flexuosa belong to var. pseudomuyldermansii, which is recognised by Hodgetts et al. (Citation2020). However, Townsend (Citation1995, Citation2007) provided evidence from Asia that var. pseudomuyldermansii is not distinct from the type, and therefore we do not distinguish the varieties here.

176 Hodgetts et al. (Citation2020) ascribe the varietal epithet glacialis to Bridel. In describing the basionym Bryum glaciale, Bridel (Citation1826–Citation1827) attributed the name to Schleicher but did not unequivocally associate him with the validating description (ICN Art. 46.2, 46.5). The citation ‘Schleich. ex Brid.’ is therefore appropriate.

177 Hanusch et al. (Citation2020) have recently described Epipterygium atlanticum Hanusch as a new species from Macaronesia, with a single record from Britain (Aberdeen, Scotland). A full appraisal of its status and morphological definition in Britain (and probably also Ireland) is needed.

178 The treatment of Zygodon stirtonii as a full species follows Mazimpaka and Lara (Citation2014). In publishing Z. stirtonii Stirton (Citation1873) ascribed the name to Schimper and clearly did not intend to be its author. However, the wording of the diagnosis appears to be Stirton's own, not Schimper's, so the ‘ex’ citation is correct (ICN Art. 46.5).

179 Zygodon forsteri was transferred to Codonoblepharon by Goffinet et al. (Citation2004) on the basis of molecular data.

180 Orthotrichum cupulatum var. riparium is recognised by Hodgetts et al. (Citation2020), but it is incompletely distinct in Britain and Ireland. Lewinsky-Haapasaari (Citation1998) similarly noted for Scandinavia that ‘it is most likely an environmental modification and not worthy of any taxonomic status’. We therefore follow Smith (Citation2004) and Hill et al. (Citation2008) in not accepting the variety here.

181 Medina et al. (Citation2012) showed that Orthotrichum consimile is a complex of four species, of which one occurs in Europe. The correct name for the European species is O. columbicum.

182 Orthotrichum scanicum was reported from Derbyshire, new to Britain, by Blockeel (Citation2012).

183 Orthotrichum rogeri was reported from Sussex, new to Britain, by Bosanquet (Citation2015).

184 Orthotrichum schimperi was not recognised as distinct from O. pumilum by Smith (Citation2004) and Hill et al. (Citation2008). However Blockeel (Citation2019) revised herbarium material and found that both taxa are present in Britain. We recognise them as distinct species here following Hodgetts et al. (Citation2020).

185 Orthotrichum cambrense was described as a new species from Wales (Carmarthenshire) by Bosanquet and Lara (Citation2012).

186 Orthotrichum alpestre was reported from Banffshire, new to Britain, by Blockeel and Lara (Citation2015). Hodgetts et al. (Citation2020) ascribe the name to Bruch & Schimp. However, in describing the species in Bryologia Europaea, Bruch and Schimper attributed the name to Hornschuch, but without unequivocally associating him with the validating description (ICN Art. 46.2, 46.5). The citation ‘Hornsch. ex Bruch & Schimp.’ is therefore appropriate.

187 Orthotrichum patens was reported from Suffolk and Derbyshire, new to Britain, by Blockeel and Fisk (Citation2018).

188 Plášek et al. (Citation2015) proposed that the genus Orthotrichum should be restricted to species with cryptopore stomata, and they proposed that the monoicous species with phaneropore stomata should be accommodated in the genus Dorcadion Adans. ex Lindb. However the name Dorcadion is illegitimate and Lara, Garilleti, et al. (Citation2016) created the new genus Lewinskya to replace it.

189 Lewinskya acuminata was reported from Derbyshire, new to Britain, by Blockeel (Citation2009).

190 Using molecular data, Vigalondo et al. (Citation2019) showed that Lewinskya fastigiata (Bruch ex Brid.) Vigalondo, F.Lara & Garilleti should be recognised as distinct from L. affinis. British and Irish material of L. affinis s.lat. has not yet been revised in the light of this conclusion, but it is very probable that L. fastigiata occurs here, having previously been reported by Spruce (Citation1845) and Wilson (Citation1855).

191 Plášek et al. (Citation2015) created the new genus Plenogemma for the dioicous species Ulota phyllantha. Mitogenomic studies by Sawicki et al. (Citation2017) support its recognition.

192 Plášek et al. (Citation2015) created the new genus Pulvigera for the dioicous species Orthotrichum lyellii. Mitogenomic studies by Sawicki et al. (Citation2017) support its recognition.

193 Caparrós et al. (Citation2016) reinstated Ulota crispula and U. intermedia as distinct taxa at species level. Blockeel (Citation2017a) applied their criteria to British and Irish material.

194 The segregation of Orthotrichum gymnostomum and O. obtusifolium in Nyholmiella is supported by molecular evidence in the studies of Goffinet et al. (Citation2004) and Sawicki et al. (Citation2010).

195 The treatment of infraspecific taxa in Fontinalis antipyretica at subspecies rank follows Hill et al. (Citation2006) and Hodgetts et al. (Citation2020).

196 Fontinalis antipyretica var. cymbifolia has leaves that are deeply channelled but not keeled. It has long been recognised in Britain and Ireland, and Lockhart et al. (Citation2012) noted its occurrence at several recently discovered localities in Ireland. However F. antipyretica exhibits great morphological diversity, and in the absence of evidence that var. cymbifolia is genetically distinct we follow Hodgetts et al. (Citation2020) in reducing it to synonymy with the type.

197 We follow Hodgetts et al. (Citation2020) in treating Fontinalis squamosa var. curnowii as synonymous with the type.

198 We follow Hill et al. (Citation2008) in treating Plagiothecium denticulatum var. undulatum as synonymous with the type.

199 Wolski and Nowicka-Krawczyk (Citation2020) have recently reinstated Plagiothecium longisetum Lindb. as a species distinct from P. nemorale. They cite several specimens of P. longisetum from Britain and Ireland. Further specimens are cited by Wolski et al. (Citation2020). A full appraisal of the status of P. longisetum in Britain and Ireland is needed.

200 Kučera and Hedenäs (Citation2020) confirmed that the genetic affinities of Campyliadelphus elodes are with Palustriella and Cratoneuron, and they transferred it to the new genus Kandaea.

201 The molecular analyses of Schlesak et al. (Citation2018) and Kučera et al. (Citation2019) place Hypnum bambergeri within Campylium in the Amblystegiaceae.

202 Kučera et al. (Citation2019) pointed out that Campyliadelphus (Kindb.) R.S.Chopra is an unnatural genus. They wrote ‘we propose conservatively to retain Campyliadelphus for the moment at the cost of leaving Campylium (including Hypnum bambergeri) paraphyletic. The potential transfer of C. chrysophyllus to Campylium would also necessitate the segregation of C. elodes, which was found to be related to Cratoneuron filicinum, to a new genus or its inclusion in Cratoneuron’. In a subsequent paper, Kučera and Hedenäs (Citation2020) confirmed the transfer of C. chrysophyllus to Campylium.

203 Amblystegium serpens var. salinum is probably an ecotype of extreme and usually saline habitats, and we follow Hodgetts et al. (Citation2020) in treating it as a synonym of the type.

204 Hodgetts et al. (Citation2020) ascribe the basionym of Conardia compacta to ‘Drumm. ex Mull.Hal.’. However in describing Hypnum compactum, Müller (Citation1849–Citation1851) does not use the epithet in the same combination as Drummond, and therefore the basionym should be attributed to Müller alone (ICN Art. 46.4).

205 The inclusion of Pseudocalliergon in Drepanocladus follows Hedenäs and Rosborg (Citation2008).

206 Hodgetts et al. (Citation2020) ascribe the combination Drepanocladus trifarius to ‘Broth. ex Paris’, but the combination by Brotherus in Engler and Prantl (Citation1887–Citation1915) was published earlier, in 1908 (Tropicos database).

207 Oliván et al. (Citation2007) showed that Hygrohypnum smithii, H. molle and H. duriusculum are in a separate clade from other species traditionally included in Hygrohypnum. Ochyra (Citation2013) recognised Platyhypnum as a valid name at generic level for these species.

208 Hodgetts et al. (Citation2020) ascribe the basionym of Platyhypnum molle to ‘Dix. ex Hedw.’. ‘Dix.’ is a typographic error for ‘Dicks’, but in any case the basionym Hypnum molle Hedw. is a conserved name with a neotype without any reference to Dickson.

209 Vanderpoorten and Hedenäs (Citation2009) provided evidence from molecular data to confirm that Amblystegium confervoides does not belong in Amblystegium and should be recognised in Serpoleskea. Hodgetts et al. (Citation2020) ascribe the combination Serpoleskea confervoides to Schimper, but it was made by Loeske (Citation1905). Serpoleskea was not a valid genus in Schimper's lifetime.

210 Gardiner et al. (Citation2005) and Ignatov et al. (Citation2007) provided molecular evidence for the separation of Campylidium (Kindb.) Ochyra from Campylophyllum. However, Campylidium is an illegitimate name and Goffinet et al. (Citation2009) replaced it with Campylophyllopsis.

211 Vanderpoorten and Hedenäs (Citation2009) provided evidence from molecular data to confirm that Amblystegium radicale does not belong in Amblystegium and should be recognised in Pseudocampylium.

212 Microhypnum sauteri was reported from West Sutherland, new to Britain, by Rothero (Citation2020b). Hypnum sauteri was transferred to the new genus Microhypnum by Kučera, Kuznetsova, et al. (Citation2019).

213 Ignatov and Ignatova (Citation2004) transferred Hygrohypnum ochraceum and H. polare to a new genus Hygrohypnella. Oliván et al. (Citation2007) confirmed that these two species are genetically distinct from other species traditionally included in Hygrohypnum.

214 Gardiner et al. (Citation2005) and Ignatov et al. (Citation2007) provided molecular evidence for the inclusion of Pseudoleskea Schimp. and Ptychodium Schimp. in Lescuraea.

215 Hodgetts et al. (Citation2020) attribute the combination Lescuraea plicata to Brotherus. However, Brotherus (Citation1892) ascribes the combination to Lindberg and acknowledges Lindberg's contribution in the introduction to his paper. The combination is therefore correctly attributable to Lindberg (ICN Art. 46.5).

216 Hodgetts et al. (Citation2020) attribute the species epithet circinatum to Bruch, but the basionym Hypnum circinatum was published by Bridel (Citation1812).

217 Huttunen and Ignatov (Citation2010) showed that the genus Platyhypnidium M.Fleisch. is polyphyletic and most of its species are found within a Rhynchostegium clade. Thus Platyhypnidium is not sustainable, and P. riparioides and P. lusitanicum should be placed in Rhynchostegium.

218 Hodgetts et al. (Citation2020) attribute the basionym of Cirriphyllum crassinervium to Taylor, but although the name Hypnum crassinervium was due to Taylor, the description was by Wilson (in Supplement to the English Botany of the late Sir J. E. Smith and Mr. Sowerby: 2: 2706. 1831).

219 Oxyrrhynchium pumilum has been placed in numerous different genera. Aigoin et al. (Citation2009) showed that it merits recognition in a monotypic genus Microeurhynchium.

220 Hodgetts et al. (Citation2020) attribute the basionym of Scleropodium cespitans to Wilson ex Müll.Hal. However, Wilson's name was Hypnum caespitosum, which is illegitimate. Müller (Citation1849–Citation1851) coined a similar name to replace it.

221 British material of Eurhynchiastrum pulchellum was studied by Hill (Citation1993) and was found to belong to var. diversifolium. We follow Guerra (Citation2016) in treating E. diversifolium as a distinct species.

222 Homalothecium lutescens var. fallax is recognised by Hodgetts et al. (Citation2020), but it has no support from molecular data in the consensus tree included in Hedenäs et al. (Citation2014). Therefore we follow Hill et al. (Citation2008) and previous British and Irish checklists in treating it as a synonym of the type.

223 Hypnum resupinatum is often treated at species level, and molecular data support its status as a taxon distinct from H. cupressiforme s.str. (Kučera et al. Citation2019). Although Hodgetts et al. (Citation2020) accept it as a full species, they note that ‘it might equally be treated as a variety of Hypnum cupressiforme’. We prefer the latter treatment. It is a troublesome taxon morphologically and some morphotypes of H. cupressiforme in Britain and Ireland mimic it closely (Preston and Hill Citation2019, p. 277).

224 Kučera et al. (Citation2019) show that Hypnum imponens is in a clade together with Callicladium haldanianum (Grev.) H.A.Crum which is sister to the clade that includes Hypnum cupressiforme. They accordingly use the combination Callicladium imponens. In our opinion, Callicladium H.A.Crum thus defined is morphologically poorly delimited and we propose transferring C. haldanianum (not present in Britain or Ireland) back to Hypnum.

225 Schlesak et al. (Citation2018) and Kučera et al. (Citation2019) provided molecular evidence for the placement of Hypnum callichroum and H. hamulosum in Stereodon and the recognition of this genus in a separate family Stereodontaceae.

226 Hodgetts et al. (Citation2020) ascribe the combination Stereodon callichrous to Lindberg, but it was validated by Bridel (Citation1826–Citation1827) in the Index to volume 2 of his work.

227 Câmara et al. (Citation2018) showed that Hygrohypnum eugyrium and H. subeugyrium belong in the Pylaisiaceae and that their placement in Pseudohygrohypnum is justified.

228 Pseudohygrohypnum subeugyrium was confirmed as a longstanding but neglected British species by Blockeel et al. (Citation2019).

229 Câmara et al. (Citation2018) transferred Hypnum revolutum to the newly defined genus Roaldia. However recent authors have not agreed on the treatment of H. revolutum var. dolomiticum (Milde) Mönk. Câmara et al. (Citation2018) did not recognise it at any taxonomic rank, but it is accepted as a full species Roaldia dolomitica (Milde) Hedenäs, Schlesak & D.Quandt by Schlesak et al. (Citation2018) and Kučera et al. (Citation2019). It has been recorded only once in Britain (Scotland), in 1932, and we regard its presence as doubtful in the absence of molecular confirmation. Therefore we do not list it here.

230 Câmara et al. (Citation2018) showed that genetically Hypnum vaucheri is distantly related to Hypnum cupressiforme and belongs in the Pylaisiaceae. They transferred it to the new genus Buckia.

231 Câmara et al. (Citation2018) showed that Ctenidium procerrimum belongs in the Pylaisiaceae and that its placement in Pseudostereodon is justified.

232 Ochyra and Stebel (Citation2008) transferred Rhytidiadelphus triquetrus to Hylocomiadelphus. Molecular analysis by Ignatov, Ignatova, et al. (Citation2019) showed that R. triquetrus was nested within species of Hylocomium in its broad traditional sense, thus providing support for the recognition of Hylocomiadelphus.

233 Hodgetts et al. (Citation2020) attribute the combination Hylocomiastrum pyrenaicum to M. Fleischer, but it was published by Brotherus (in Engler and Prantl Citation1887–Citation1915). Brotherus ascribed the name to Fleischer but did not indicate that Fleischer made a special contribution to the work (ICN Art. 46.2, 46.5). The citation ‘M.Fleisch. ex Broth.’ is therefore appropriate.

234 Refer to the annotation for Hylocomiastrum pyrenaicum for an explanation of the author citation here.

235 Hodgetts et al. (Citation2020) attribute the genus Cryphaea to D. Mohr. However the genus was published by Weber (Citation1814) in a work published by C. F. Mohr.

236 Hodgetts et al. (Citation2020) attribute the combination Cryphaea heteromalla to D. Mohr. However the combination was made by Bridel (Citation1819).

237 Crosby and Buck (Citation2011) pointed out that Pterogonium Sw. is an illegitimate name, and they created Nogopterium to replace it.

238 Stech et al. (Citation2011) and Werner et al. (Citation2015) found insufficient evidence to justify continued recognition of Leucodon sciuroides var. morensis and we follow them here.

239 Olsson et al. (Citation2011) segregated Alleniella S.Olsson, Enroth & D.Quandt and Exsertotheca S.Olsson, Enroth & D.Quandt from Neckera. They comment: ‘the typical Neckera characters (deeply undulate, glossy, complanate and asymmetric leaves and a weak costa) seem to represent the ancestral state and were later lost independently in Leptodon and Forsstroemia’. Their taxonomic solution is to create further (slightly artificial) genera in order to retain the two latter genera, when these genera could simply have been sunk rather painlessly into Neckera, especially since most groups in the Neckera clade comprise species that are currently placed in that genus. We consider that the data equally justify the retention of a larger Neckera s.lat., incorporating Leptodon D.Mohr and Forsstroemia Lindb.

240 Hodgetts et al. (Citation2020) attribute the genus Homalia to (Brid.) Bruch & Schimp. However Homalia Brid., Bryol. Univ. 1: xlvi; 2: 807, 812 is a conserved name.

241 Ignatov, Fedorova, et al. (Citation2019) showed that Anomodon attenuatus is genetically closer to the Neckeraceae than to Anomodon viticulosus. They raised Pseudanomodon to generic rank to accommodate it.

242 Ignatov, Fedorova, et al. (Citation2019) showed that Heterocladium dimorphum is strongly differentiated genetically from H. heteropterum, and they placed it in a separate genus Heterocladiella. However, its taxonomic relationships with the Lembophyllaceae and Neckeraceae require further study.

243 We follow Hodgetts et al. (Citation2020) in recognising Heteropterum flaccidum as a full species. However, its morphological separation from reduced forms of H. heteropterum and H. wulfsbergii remains problematic (Hill et al. Citation2008).

244 Hodgetts and Vanderpoorten (Citation2018) provided evidence that Isothecium myosuroides var. brachythecioides should be recognised as a full species, for which the earliest name is I. interludens.

245 Ctenidium molluscum exhibits an enormous range of morphological variation. However the vars. condensatum and robustum intergrade with the type and no genetic basis for their recognition has yet been found. We follow Hodgetts et al. (Citation2020) in not recognising infraspecific taxa within this species.