Pylaisia afoninae B. H. Allen & W. R. Buck, 2015

Pylaisia afoninae B. H. Allen & W. R. Buck , sp. nov.

Fig. 1 View Fig : A–J

Plants medium sized in reddish-tinged to golden mats. Stems creeping, to ca. 2 cm long, irregularly branched, the branches to 6 mm long; cross-section with 3–6 rows of small, thick-walled cells surrounding abruptly larger, thin-walled cells, central strand weakly developed; axillary hairs with all cells pale yellow, with a single, short, basal cell and (2–)4–6 rectangular apical cells; pseudoparaphyllia complex, subfilamentous to the outside, foliose with deeply and broadly incised margins to the inside; rhizoidal initials abaxial to leaf insertions; rhizoids slender, smooth, red, not or sparsely and irregularly branched. Branch and stem leaves similar, densely foliate, wrinkled, appressed-imbricate when dry, erect when moist, oblong-ovate, short-decurrent, rounded to the insertion, 1.47–1.75 × 0.75–0.86 mm, ± abruptly long-acuminate, the acumen ca. 1/4–1/5 the leaf length, concave, somewhat plicate; margins subentire throughout, plane throughout or occasionally erect on one side below; costa short and double; laminal cells linear-fusiform, 33–55 × 5.5–8.0 µm, thin-walled, not significantly shorter toward apex or insertion but thick-walled and porose at insertion; alar region opaque, well developed, restricted to basal corners and not reaching costa, cells quadrate to oblate, ca. 12–15 cells across insertion and 10–15 cells up the margins, decurrent by 1–2(–3) enlarged cells in extreme corners, often remaining on stems upon dissection. Asexual propagula not seen. Dioicous (?). Perigonia bud-like, sessile along main stems, 0.6–0.8 mm high; leaves ovate, 0.6 mm long, acute; margins plane, subentire; costa absent; paraphyses numerous. Perichaetia not seen.

TYPE. PERU. Cajamarca: Celendin, La Tranca-Gelig ( Celendin ), 6°35’28"S, 79°03’46"W, 2800 m; sobre rocas; 18 Aug 1984, A. Sagástegui 12148A (with J. Mostacero L. & S. Leiva G.) (holotype MO; GoogleMaps isotypes MHA, GoogleMaps NY) GoogleMaps .

Pylaisia afoninae is a high elevation moss with medium-sized, reddish to golden plants that grow in dense mats with irregularly to subpinnately branched stems and prostrate or ascending branches. Its stems have complex, subfilamentous to foliose pseudoparaphyllia with deeply and broadly incised margins; very thick-walled epidermal cells and weakly developed central strands. The gametophytes of P. afoninae are odd for Pylaisia because their leaves are wrinkled, appressed-imbricate when dry; this gives the plants a somewhat turgid aspect. Pylaisia afoninae has stem leaves that are strongly concave and typically rounded at base. The leaves have plane, subentire margins; smooth, linear-fusiform cells; short, but distinct double costae; weak leaf decurrencies; and remarkably well-developed, opaque alar regions with quadrate to oblate cells that extend 10–15 cells up the basal margins. An interesting feature of P. afoninae is the presence below the alar cells of 1–2(–3) enlarged, hyaline cell(s) that are very similar to the inflated basal cells encountered in Ectropothecium leptochaeton (Schwägr.) W.R. Buck. All species presently placed in Pylaisia are autoicous, but P. afoninae appears to be dioicous: only perigonia have been observed. Another of the odd features of P. afoninae is its occurrence on rocks in an overwhelmingly corticolous genus.

Pylaisia falcata is comparable in size to P. afoninae and sometimes grows on rocks. Furthermore, both species have similarly shaped leaves with long-acuminate apices. However, it differs from P. afoninae in its autoicous sexual condition and in having silky plants with typically falcate-secund to circinate, almost flat leaves. In addition, the leaves of P. falcata have poorly developed alar regions with only 2–6 oblate, quadrate, or subrectangular, hyaline, thick-walled alar cells at the basal margins. Hypnum vaucheri Lesq. is remarkably similar to P. afoninae in size, leaf shape, alar cell development, and in having linear-fusiform leaf cells. In addition, H. vaucheri often grows on rocks or soil, is dioicous, and has broadly foliose pseudoparaphyllia with dentate or ciliate margins. However, the typical form of H. vaucheri differs from P. afoninae in having smoothly falcate-secund leaves and its pseudoparaphyllia are never as broadly and deeply incised as those of P. afoninae . Although there is an arctic-alpine, julaceous form of H. vaucheri with compactly appressed, straight leaves ( H. vaucheri fo. tereticaulis Ando ), this form differs from P. afoninae in having small plants with broadly ovate leaves and very short, broad leaf cells. Nevertheless, H. vaucheri is a widespread, exceedingly variable species and it is possible that P. afoninae represents a previously unrecognized form of the species. The strongest evidence for a placement of this taxon in Pylaisia is the presence of its deeply and broadly incised pseudoparaphyllia (see, Arikawa, 2004, Figs. 6G, 6I, 6N). Whether the taxon belongs in Pylasia or Hypnum can only be definitively determined by the discovery of its sporophytes.