Plagiothecium schofieldii G.J.Wolski & W.R.Buck, 2021

Wolski, Grzegorz J., Nowicka-Krawczyk, Paulina & Buck, William R., 2021, Plagiothecium schofieldii, a new species from the Aleutian Islands (Alaska, USA), PhytoKeys 184, pp. 127-138 : 127

Plagiothecium schofieldii G.J.Wolski & W.R.Buck sp. nov.

Type.

U.S.A. Alaska, Shumagin Islands, Simeonof Island, mainly near saddle between Hill 1436 and 1265, wet cliff chimney, 54°55'N, 159°15'W, 19 July 1996, W.B. Schofield 106119, Holotype MO 5135779 .

Description.

Plants small, light green to yellow, with a delicate metallic luster, forming very dense, often homogeneous mats. Stems erect, 1.5-3.0 cm long (Fig. 3 ), in cross-section rounded, with a diameter of 300-380 μm, the central strand developed, epidermal cells 10-25 × 6-12 μm, the parenchyma thin-walled, 20-40 × 15-32 μm; leaves julaceous, imbricate, very closely arranged on the stem, when dry not shrunken, very concave, therefore very often damaged under the microscope, symmetrical, ovate to elliptic, those from the middle of the stem 1.4-3.0 mm long, and the width measured at the widest point 0.9-1.9 mm; the apex obtuse and apiculate, often denticulate; costae two, thick and strong, extending usually to ½ of the leaf length, reaching 0.5-2.0 mm; laminal cells linear, rather symmetrical, in quite regular transverse rows, the length and width very variable but dependent on location: 66-178 × 14-33 μm at apex, 88-190 × 13-29 μm at midleaf, and 45-221 × 20-39 μm toward insertion, due to the very wide cells, cell areolation clearly loose; decurrencies of 4-5 rows of rounded, rounded-rectangular, inflated cells, 40-90 × 22-48 μm, forming distinct, quite long auricles, 300-750 μm long (Fig. 4 ). Autoicous. Sporophytes abundant; setae dark brown at base, yellowish-orange at apex, twisted when dry, 1.8-2.3 cm long; the capsules more or less erect, 700-950 × 280-350 μm; operculum short and rostellate; peristome double, well developed, 450-500 μm long; exostome teeth trabeculate at the ventral side.

Etymology.

The present species is named in honor of Wilfred “Wilf” Borden Schofield (1927-2008), who spent decades studying northern regions of North America, including the Aleutian Islands, and who on July 19, 1996, collected the specimen (No. 106119), chosen here as the holotype of Plagiothecium schofieldii . According to Stephen Talbot (pers. comm.), Schofield recognized this plant as distinct in the field.

Distribution and ecology.

Plagiothecium schofieldii so far has only been recorded from Adak Island, Attu Island and Simeonof Island in Alaska. In this area it has been recorded on wetlands and hills, wet cliff chimney, open, moist crevice of a cliff, shaded face of hole on slope, shaded humid outcrop, along creek and adjacent slope, near saddle between hills and near base of mountain.

Additional specimens examined.

U.S.A. Alaska: Adak Island, Finger Bay, along creek and adjacent slope, open, moist, crevice of cliff, 15-30 Jun 1975, D. K. Smith 3864 (NY02589541); Attu Island , near Jaemin Pass , slopes of Ribson Ridge , shaded face of hole on slope, 52°53'N, 173°10' W, 10 Aug 2000, W. B. Schofield & S. S. Talbot 115646, UBC ACC# B185126; Shumagin Islands , Simeonof Islands , near base of larger mountain, N. side, 54°55'N, 159°15' W, shaded humid outcrop, 17 Jul 1995, W. B. Schofield, S. S. Talbot & G. Argus 104056, ACC# B159650 (MO5140205); wetlands and Hill 624, 54°55'N, 159°15'W, seepy cliff chimney, 7 Jul 1996, W. B. Schofield 105769, ACC# B161483 (MO5148015) .

Figures

Figure 3. Stems with the sporophytes of Plagiothecium schofieldii. Part of the turf of holotype (W. B. Schofield 106119, MO 5135779). Scale bar: 1 cm.

Figure 4. The most important taxonomic features of Plagiothecium schofieldii. Dimensions of cells from the apex A the middle B and basal part of the leaf C leaves D-E leaf apex F auricles G. Scale bar: 100 µm (A-C, F-G); 500 µm (D-E). Photos from the holotype (W. B. Schofield 106119, MO 5135779).