Plagiothecium semimortuum var. macquariense G.J.Wolski, 2024

Wolski, Grzegorz J., Latoszewski, Mikolaj, Cargill, D. Christine & Buck, William R., 2024, Re-assessment of type material of Plagiothecium novae-seelandiae Broth. and descriptions of four new Plagiothecium taxa (Bryophyta, Plagiotheciaceae) from Australasia, PhytoKeys 238, pp. 95-117 : 95

Plagiothecium semimortuum var. macquariense G.J.Wolski var. nov.

Type.

Holotype: Australia, Tasmania , Macquarie Island, NW slope of Mt. Haswell, Caroline Cove, 54°44'S, 158°51'E, in Poa foliosa dominated vegetation on northwest slopes of Mt. Haswell , 120 m alt., leg. R. D. Seppelt 15316, 30 Jan. 1985 (HO610220!) .

Description.

Plants small, ascending and julaceous, yellow-green, with metallic luster, forming dense mats; stems 0.5-1.0 cm long, in cross-section rounded, with a diameter of 250-280 μm, the central strand well-developed, epidermal cells thick-walled, 7-13 × 6-11 μm, the parenchyma thin-walled, 9-11 × 8-10 μm; leaves symmetrical, narrowly ovate, folded, imbricate, closely arranged on the stem, concave, therefore leaves splitting when flattened, leaves from 1/3 up to 2/3 without protoplasts, those leaves from the middle of stem 1.9-2.2 mm long and the width measured at the widest point 0.9-1.1 mm; the apex acute and denticulate; costae two, rather thick and strong, extending usually to ⅓ of leaf length; laminal cells more or less symmetrical, length and width variable but dependent on location: 112.5-140 × 7.5-10 μm at the apex, 112.5-125 × 7.5-10 μm at midleaf, 88-112 × 15 μm toward insertion; due to the width of the cells, cell areolation tight; decurrency of 4-5 rows of rounded and inflated cells, forming distinct auricles, 200 μm long; sporophytes so far unknown; sexual condition unknown (Figs 9 , 10 ).

Plagiothecium semimortuum var. macquariense so far has been recorded from Australia - Macquarie Island (HO610219, HO610227, HO610220) and mainland Tasmania (HO71698) (Fig. 11 ). Specimens were noted in Poa foliosa (Hook.f.) Hook.f. dominated vegetation on northwest slopes of Mt. Haswell (HO610220); in Pleurophyllum Hook.f. dominated plateau herbfield (HO610219); on undercut bank at edge of creek (HO610227). Each specimen of P. semimortuum var. macquariense was collected in lowland areas (70 to 200 m alt).

Etymology.

The name of this variety - Plagiothecium semimortuum var. macquariense - refers to Macquarie Island (Australia, Tasmania), from which the plant was first recorded, and where the holotype (HO610220) was collected.

Figures

Figure 3. Selected taxonomic features of P. lamprostachys A shape and dimensions of the leaf B leaf apex C cells from the middle part of the leaf D leaf basal cells (from the type of material of H. lamprostachys BM 000677528!, photo. G. J. Wolski, 01 August 2023).

Figure 9. Selected taxonomic features of Plagiothecium semimortuum var. macquariense A, B shape and dimensions of leaf C julaceous turf D dimensions and shape of cells from middle part of the leaf (from the type of P. semimortuum var. macquariense HO 610220, photo. G. J. Wolski, November 13, 2022).

Figure 10. Comparison of leaf shapes and dimensions of all described taxa A P. novae-seelandiae var. brotheri B P. novae-seelandiae var. novae-seelandiae C P. lamprostachys D P. semimortuum var. macquariense E P. semimortuum var. semimortuum F P. funale G P. cordatum (based on the types of the above-mentioned taxa, see Figs 3 - 9).

Figure 11. Distribution of the newly described taxa. Explanation: white triangles - P. semimortuum var. semimortuum; yellow circles - P. semimortuum var. macquariense; purple circles - P. novae-seelandiae var. brother; aquamarine squares - P. cordatum (Google Maps, accessed September 15, 2023).