Hyophila flavolimbata S. He

Yi, Yan-Jun, He, Si & Ma, Wen-Zhang, 2015, Hyophila flavolimbata, a new species of Pottiaceae from northwestern Yunnan, China, Phytotaxa 231 (2), pp. 182-186 : 183-185

Hyophila flavolimbata S. He & Y.-J. Yi, sp. nov. ( Figs. 1 & 2 )

Diagnosis: —It differs from Hyophila involuta by a differentiated leaf marginal border consisting of 3–4 rows of lightly yellowish thick-walled cells, leaf cells completely plane on both abaxial and adaxial leaf surfaces, a reddish stem with papillose epidermal cells, a layer of pseudoleptoids next to hydroids in central strand, and the presence of subguide cells in costa.

Type: — CHINA. Yunnan: Gongshan County, Eastern slope of the Gaoligongshan. Along road 2.5 km from tunnel at Heipu Pass , 49 km from the city of Gongshan , at roadside, on seeping rock, alt. 3365 m, 27°46’48” N, 98°27’29” E, 13 Sept. 2013, Ma et al. 13-4879 (holotype, KUN; isotypes, CAS, E, MO) ; Shevock et al. 43028 (paratypes, CAS, E, KUN, MO) .

Plants small to medium-sized, dull green to dark green above, reddish brown below, in loose tufts. Stems erect, simple, 17–25(–35) mm tall, reddish, sparsely foliate in lower part of stems; in cross section stem epidermis consisting of 1–2 layers of thick-walled cells, papillose on stem surface, cortical cells thin-walled, a central strand strongly differentiated, a layer of pseudoleptoids (reddish thick-walled cells) present next to hydroids in the central strand; axillary hairs 5–10 cells long, with elongate upper cells and shorter basal cells, all hyaline. Leaves widely spreading when wet, slightly contorted when dry, spathulate to oblong-obovate or broadly ligulate, 1.6–2.2 × 0.9–1.2 mm, widest part above leaf middle, narrowed toward the base, obtusely apiculate at apex, not decurrent, often incurved on one side at leaf base; margins plane, denticulate to dentate above, entire below, bordered by 3–4 rows of thick-walled cells, forming a distinct, light-yellowish band; costa subpercurrent, ventral surface cells rectangular to elongate-rectangular, two stereid bands present, guide cells 4–6 in 1 layer, subguide cells 4–5 present on dorsal side of the guide cells; upper and median leaf cells rounded quadrate, 15–20(–25) μm in width, moderately thick-walled, median cells often with corner thickenings, plane or weakly convex on both abaxial and adaxial leaf surfaces; basal leaf cells short- to elongate-rectangular, 20–60 × 15–25 μm, hyaline, thin- to moderately thick-walled. Brood branches present. Perigonia and perichaetia not seen. Sexuality unknown. Laminal KOH color reaction yellow.

Etymology: —The specific epithet taken from the Latin flavus (yellowish) and limbatus (border) refers to the differentiation of a yellowish border at leaf margin.

Conservation status: —The new species should be included into the category “not evaluated” (NE), since it is only known from a single type locality.

Distribution and habitat: —Only known from a high elevation zone in China and maybe found in other similar habitats in the region; on seeping or wet rock with moderate exposure to sunlight.

Discussion: —The most obvious feature of Hyophila flavolimbata is its Lightly brownish tangerine leaf margin bordered by 3–4 rows of thick-walled cells ( Fig. 1 , G; Fig. 2 , B). A broad marginal band of the leaves stands out clearly in water mount under a binocular stereo microscope. In addition, the following three characteristics observed in this new species are quite distinctive among Hyophila species even within the Pottiaceae . Firstly, the epidermal cells of stem are only in 1–2 layers, strongly thick-walled, and papillose ( Fig. 2 , J, L). The papillae appear to be a type of cuticular ones, sometimes strong and sometimes weak. Secondly, the presence of pseudoleptoids in the stem cross section is quite exceptional, which consists of a ring of reddish, thick-walled cells located just next to hydroids in the central strand ( Fig. 2 , F, K). This type of structure has only been seen in the Polytrichaceae . Thirdly, besides the two stereid bands on both sides of the guide cells, which are 4–6 in 1 layer, there are 4 or 5 non-stereid cells. They are somewhat smaller and positioned dorsally just next to the typical enlarged guide cells as seen from the cross section of costa ( Fig. 2 , H, I). These non-stereid cells may be regarded as a second layer of the guide cells; however, they seem to be intercepted by the stereid cells. Here, we have described them as the subguide cells.

Hyophila flavolimbata is clearly related to H. involuta , a widely distributed species in the world. Both species share some similarities in leaf shape and areolation. Besides the several characteristics discussed above, the new species is readily distinguished from H. involuta by the larger upper and median leaf cells (15–25 μm in width), which are often with corner thickenings ( Fig. 2 , D) and plane on both abaxial and adaxial leaf surfaces ( Fig. 2 , G–I). In contrast, the upper and median leaf cells of H. involuta are smaller (8–12 μm in width), without corner thickenings, and often bulging-mammillose on the adaxial leaf surface. Within the Pottiaceae , H. flavolimbata also resembles Crumia latifolia (Kindberg in Macoun 1889: 94) W. B. Schofield (1966: 610) and Scopelophila ligulata ( Spruce 1847: 331) Spruce (1881: 14) in having similar spathulate to ligulate leaf shape and a distinct marginal border formed by a few rows of thick-walled cells; but it differs from the latter two species by the presence of two stereid bands in its costa and a strong central strand in its stem. Both C. latifolia and S. ligulata have a single stereid band and no central strand. The new species is likewise similar to Ganguleea angulosa (Brotherus & Dixon in Dixon 1910: 302) R. H. Zander (1989: 427) from Himalayas in leaf shape and non-papillose leaf cells, but the latter has a single stereid band in its costa and lacks a central strand in its stem. Hyophila flavolimbata belongs to the subfamily Barbuloideae tribe Barbuleae based on the new classification of Pottiaceae ( Zander 2007) even though the genus Hyophila was placed in the subfamily Pottioideae tribe Hyophileae ( Zander 1993) or in the subfamily Trichostomoideae (Hill et al. 2006) . When fertile plants are present, the species of Hyophila are immediately recognized by their cylindrical, eperistomate capsules. Although the occurrence of stalked gemmae in the upper leaf axils has been used in the diagnosis of some species of Hyophila , their constancy has yet to be fully established for most taxa (Eddy 1990). In fact, only few brood branches have been found in the new species ( Fig. 1 , D).

Figures

FIGURE 1. A–I. Hyophila flavolimbata S. He & Y.-J. Yi. A, dry plants. B, wet plants. C, a wet branch. D, a brood branch. E–F, leaves. G, leaf apex. H–I, leaf bases. (All prepared from the isotype, Ma et al. 13-4879, MO).

FIGURE 2. A–L. Hyophila flavolimbata S. He & Y.-J. Yi. A, apical leaf cells. B, marginal leaf cells. C, basal leaf cells. D, median leaf cells. E, lower marginal leaf cells. F, J, K, cross sections of stems with a layer of pseudoleptoids pointed by arrows. G–I, cross sections of leaves with subguide cells pointed by arrows. L, part of stem cross section showing papillose epidermal cells (All prepared from the isotype, Ma et al. 13-4879, MO).