Taxonomic novelties in Scapania.

Five new supraspecific taxa of Scapania are proposed, Scapania subg. Gracilidae, Scapania subg. Pseudomacrodiplophyllum, Scapania sect. Americanae, Scapania sect. Hyperboreae, and Scapania sect. Simmonsia.

Introduction

The northern temperate leafy liverwort genus (Dumort.) Dumort. was the subject of two comprehensive molecular phylogenetic studies (Vilnet et al. 2010, Heinrichs et al. 2012). These studies provided evidence for incongruence of the present supraspecific classification (Potemkin 2002) with the molecular tree topologies. Extensive morphological homoplasy hampers a morphological circumscription of several lineages identified in the molecular studies; however, several new combinations and taxa are needed to arrive at a monophyletic supraspecific classification (Fig. 1). In the following, the new taxa are introduced.

Figure 1.

Phylogeny of with the new taxa indicated in bold. Modified from Heinrichs et al. (2012, Fig. 1).

Taxonomy

(H. Buch) Váňa, Hentschel, Joch. Müll. & Heinrichs comb. et stat. nov.

Basionym.

sect. Gracilidae H. Buch, Commentat. Biol. 3(1): 106. 1928.

Type.

Lindb., Morgonbladet (Helsinki) 1873(286): 2. 1873.

Note.

According to the molecular phylogenies presented by Heinrichs et al. (2012), sect. Gracilidae forms a lineage outside Scapania subg. ; hence, we propose subgenus rank (Fig. 1).

Váňa, Hentschel, Joch. Müll. & Heinrichs subg. nov.

Diagnosis.

subg. Pseudomacrodiplophyllum includes species which differ from other Scapania elements by the presence of multicellular gemmae with intersecting walls, basal leaf cell walls with intermediate thickenings and pluriplicate perianths.

(Mitt.) Müll. Frib., Nova Acta Acad. Caes. Leop.-Carol. German. Nat. Cur. 83: 262. 1905.

[ (Mitt.) Perss.] forms the sister clade to the rest of Scapania (Vilnet et al. 2010, Heinrichs et al. 2012); hence, a new subgenus is introduced here to accommodate this species (Fig. 1).

Váňa, Hentschel, Joch. Müll. & Heinrichs sect. nov.

The new section of subg. Scapania is characterized by its type, the dioicous Müll. Frib. Distinctive features of and sect. Americanae are thick-walled, pigmented stem epidermis cells with thinner-walled cells on the ventral side of the stem, closely and sharply ciliate-dentate leaf-margins, with largest teeth up to five cells long and terminal cells considerably longer than wide, leaf-lobes that are usually decurrent beyond the level of the keel, a verruculose or striate-verruculose cuticle, and two-celled gemmae at the margins of unmodified leaves. The dorsal leaf-lobes often develop an undulate or folded base and may even show minute lobules or auricles.

Müll. Frib., Bull. Herb. Boissier, sér. 2, 3: 44. 1902.

is placed sister to sect. Compactae (Müll. Frib.) H. Buch with weak bootstrap support (Heinrichs et al. 2012). It differs from members of sect. Compactae by its dioicous condition; hence we place it in a new section rather PageBreakthan in sect. . In our current circumscription, sect. Americanae is monospecific, however, extension of the taxon sampling in forthcoming molecular studies may disclose further representatives.

Váňa, Hentschel, Joch. Müll. & Heinrichs sect. nov.

Species of sect. Hyperboreae resemble members of sect. Curtae (Müll. Frib.) H. Buch but differ by the presence of brownish to reddish gemmae, and a usually larger size.

Jørg., Förh. Vidensk.-Selsk. Kristiania 1894(8): 56. 1894.

The presence of the type species of sect. Irriguae (Müll. Frib.) H. Buch, (Nees) Nees, in sect. Curtae necessitates the introduction of a new section for the remaining elements of sect. Irriguae. Molecular data so far supported the presence of Loeske & Müll. Frib. and (Arnell) H. Buch in subg. sect. Hyperboreae, as well as (Vilnet et al. 2010; Heinrichs et al. 2012).

(R.M. Schust.) Váňa, Hentschel, Joch. Müll. & Heinrichs comb. et stat. nov.

subsect. Simmonsia [“”] R.M. Schust., Hepat. Anthocerotae N. Amer. 3: 612. 1974.

Bryhn & Kaal., Rep. Second Norweg. Arctic Exped. Fram 2 (11): 51. 1906.

forms an isolated lineage within subg. , hence, we erect a section for this species rather than using subsectional rank (Schuster 1974). Distinctive features of the monotypic section are the deflexed-involute, broad, concave ventral leaf lobes that stand away from the stem at almost right angles and leaf cell walls with very large, nodulose trigones.