Juncus hondurensis J. Proćków, 2020

Proćków, Jarosław, 2020, Juncus hondurensis (Juncaceae), an endemic rush species new from Honduras, Phytotaxa 439 (1), pp. 93-101 : 95-98

Juncus hondurensis J. Proćków , sp. nov. — Figs. 1–3 .

Type:— HONDURAS, Dep. de Francisco Morazán: Jutiapa, 25 km NE de Tegucigalpa, bosque húmedo subtropical, pinares, 1700 m alt., 20 May 1988, I. Padilla 604 (holotype BM 907052!).

Description:—Perennial, herbs, 37.5–40 cm tall (up to 65 cm —information from the label). Rhizome (probably) densely branching ( Fig. 3 ). Culms erect, 1.3–1.4 mm diam., terete or somewhat angular (square) in some parts in x.s., weakly many-striate when dry. Cataphylls present but inconspicuous. Foliar leaves 1–2 basal and 1 cauline to each culm, lamina of basal leaves ca. 19 cm long, of cauline leaves 2.6–4.8 cm long; sheaths of basal leaves ca. 4 cm long, of cauline leaves 3.3–4.8 cm long, margins scariose and terminating in two 0.5–0.8 mm long (ca. 1.3 mm in basal leaves), scariose, rounded auricles; basal blades 1.4–1.6 mm diam., cauline blades 1–1.3 mm diam., round to elliptic in x.s., nodulated by sometimes conspicuous septa, very close together, (1.5–) 1.7–2 mm apart (in cauline leaves). Inflorescence 7–13-headed, 1–2 times branched anthela, up to 9 × 4 cm; heads semi-globose, 6.5–7.5 mm diam., many-flowered; the ultimate head bearing branches 0.4–0.5 mm diam. Lower inflorescence bract 1.2–3.4 cm long, resembling basal and cauline leaves but much shorter, distal bracts shorter, the ultimate ones scale-like and ca. 3.7 mm. long, floral bracts to ca. 3 mm long, stramineous, with scariose margins. Inner tepals shorter than outer ones (sometimes only slightly), or rarely longer. Outer tepals 2.5–3(–3.3) mm long, inner tepals 2.3–2.6(–2.8) mm long, lanceolate to broadly lanceolate, acute, castaneous or sometimes brownish-stramineous, margin scariose, outer tepals concave, inner ones slightly concave, sometimes slightly narrower than the outer ones. Stamens 6, (1.3–) 1.4–1.5 mm long; anthers oblong to linear, (0.55–) 0.65–0.75 mm long and usually shorter than the filament (rarely equalling them). Filaments (0.65–)0.75–0.85(–0.9) mm long. Capsule broadly ellipsoid to elongate-spherical, more cylindrical at the bottom (in x.s.), and three-lobed in the upper part (in x.s.), apically rounded and apiculate, (2.5–)2.7–2.9(–3) × (1.1–)1.6–1.9(–2) mm, (slightly) longer, equalling or (slightly) shorter than the tepals, light brown at the base and up to the middle, and dark brown at the apex (sometimes also lighter there), unilocular. Seeds narrowly to broadly ellipsoid, apiculate, (0.3–)0.4–0.44 × 0.16–0.21 mm, reticulate, 14–16-striate, yellow brown.

Juncus hondurensis combines features not found together in any other species of Juncus . Three species ( J. articulatus Linnaeus (1753: 327) , J. debilis , J. ebracteatus ) belong to the group of rushes of section Ozophyllum with densely branching rhizomes and the acute and trigonous capsule longer than the tepals. In J. articulatus capsules are broadly ovoid, dark castaneous to black, and in J. debilis capsules are narrowly ovoid, light brown). In J. ebracteatus capsules are extended into a 1–2 mm long beak that is terete. Capsules of J. hondurensis are, however, broadly ellipsoid to elongate-spherical, more cylindrical at the bottom (in x.s.), and three-lobed in the upper part (in x.s.), apically rounded and apiculate, light brown at the base and up to the middle, and dark brown at the apex (sometimes also lighter there); see Table 1. Moreover, J. hondurensis has 6 stamens (vs. 3 stamens in J. debilis ), and its seeds are 14–16-striate, narrowly to broadly ellipsoid, and smaller, (0.3–)0.4–0.44 × 0.16–0.21 mm (vs. seeds 24–26-striate, ovoid, 0.45–0.6 × 0.24–0.26 mm in J. articulatus ); see Table 1.

Juncus pallescens Lamarck belongs to the group of rushes of the Ozophyllum section with densely branching rhizomes and the capsule equalling or shorter than the tepals, and the ultimate peduncles> 0.45 mm diameter: its tepals are 3.0– 4.5 mm long, subequal, acuminate, and filaments (0.6–)1.0– 1.2 mm long. Other useful features are cauline leaves 10–25 cm long, 1.5–2.0 mm in x.s., perfectly (not distinctly) septate; and capsule ellipsoid to obovoid, unilocular, truncate to bluntly acute, trigonous (to trilobed in T.S.); see Table 2.

Juncus hondurensis tepals are much shorter: outer ones 2.5–3(–3.3) mm long, inner ones 2.3–2.6(–2.8) mm long, and inner tepals are shorter than outer ones (sometimes only slightly), or rarely longer, acute; filaments are also shorter: (0.65–)0.75–0.85(–0.9) mm long. Other differences can be also taken into account: J. hondurensis cauline leaves are much shorter (2.6–4.8 cm long) and thinner (1–1.3 mm diam.), sometimes perfectly distinctly septate; for capsule features of J. hondurensis see above; see Table 2.

Juncus acuminatus Michaux and J. microcephalus Humboldt, Bonpland & Kunth belong to the same group (with densely branching rhizomes and capsule equalling or shorter than tepals) but the ultimate peduncules are <0.4 mm diameter ( J. acuminatus has tepals soft, capsule trigonous, valves inflexed along the margins at maturity, and 3 stamens (N America to Honduras), and very variable J. microcephalus has tepals soft as well, but capsule round, and valves inflexed at the apex at maturity). While the ultimate head-bearing branches of J. hondurensis are 0.4–0.5 mm diameter, tepals are rigid, and capsules different (see above). Furthermore, J. hondurensis has 14–16-striate seeds (vs. 16–20-striate ones in J. microcephalus ), semi-globose heads (vs. conical to globose ones in J. microcephalus ), shorter filaments, (0.65–)0.75–0.85(–0.9) mm long (vs. c. 1 mm long in J. microcephalus ), and a few less significant differences in cauline leaf features and length, stem in x.s. and sheath length; see Table 3.

Distribution:—Known only from locus classicus ( Honduras, Dep. de Francisco Morazán: Jutiapa, 25 km NE de Tegucigalpa) from the subtropical humid pine forest.

General comments:—The species requires further research. In herbaria I have not found a similar specimen, having searched personally several large collections, e.g., E, K, MA, P, and databases with images of many others. Even in the native herbarium, which is listed on the herbarium label (Herbario Universidad Nacional Autónoma de Honduras, Tegucigalpa (former acronym UNAH, now TEFH)), no duplicate of this specimen has been found. Further research in the field is necessary in the Mesoamerica region, especially in similar habitats, i.e., subtropical humid pine forests, and at a similar height above sea level (ca. 1700 m alt.). As this new taxon is known from only one locality, the species may be considered Critically Endangered (CR) following the IUCN criteria for endangered species, and it is therefore considered to be facing an extremely high risk of extinction in the wild. The specific epithet, hondurensis , refers to the country it is described from.

Figures

FIGURE 1. Juncus hondurensis J. Proćków. Flowers (A–D, F–G), fruit (A–D, F) and anthers (B, E–F). Images from the holotype (views of different heads on the plant). Red arrow indicates the insertion of the filament. Scale bars, 1 mm.

FIGURE 2. Juncus hondurensis J. Proćków. Seeds (A–D). Images from the holotype.

FIGURE 3. Juncus hondurensis J. Proćków. The holotype sheet with the habit of the plants and magnifications of the inflorescence (middle right) and the bottom part of the plants (top left).