Selaginella dushanensis J. K. Huang & S. Y. Dong sp. nov.

Figs 3, 4

Type.

China • Guizhou: Dushan County, Jia Feng Yan; 25°59'15"N, 107°40'15"E, elev. 770 m, in evergreen broadleaf forest, 7 November 2024, S. Y. Dong & J. K. Huang D 6750 (holotype, IBSC, barcode 1047559; isotypes: IBSC -1047560, PE).

Diagnosis.

Selaginella dushanensis is similar to S. monospora and S. submonospora, but differs from the latter two mainly by its median leaves with long aristate apices (vs. apices acuminate in S. submonospora or short aristate in S. monospora). This new species is morphologically also similar to S. effusa and S. subeffusa, but differs by its lateral leaves with the upper bases not overlapping stems (vs. distinctly overlapping stems in the latter two).

Description.

Terrestrial, creeping, 10–30 cm long; rhizophores restricted throughout the creeping stems and branches, singly borne on ventral side in the axils of branches, reddish, glabrous; main stem branched from the base, terete, glabrous, stramineous in colour, 0.7–1.0 mm in diam., 5.0–8.0 mm wide including leaves; primary branches alternate, 1.0– 2.5 cm apart along the main stem, once or twice pinnately branched, with ultimate branches including leaves being 3.0–5.0 mm wide; vegetative leaves herbaceous, dimorphic, arranged in four rows (two dorsal and two ventral); axillary leaves symmetrical, those on main stems slightly larger than those on branches, elliptic to ovate, 1.7–2.5 × 0.8–1.5 mm, base cuneate to obtuse, apex acuminate, margin denticulate; median leaves asymmetrical, slightly carinate, those on main stems larger than those on branches, slightly distant on main stems and imbricate on distal portions of stems and branches, ovate or broadly ovate, 0.8–1.7 × 0.6–1.3 mm, base obliquely shallowly cordate with the outer potion obviously narrower than the inner portion, margin denticulate or denticulate-ciliolate, apex long aristate (arista ca. 2 / 3 to as long as the leaf blade); lateral leaves asymmetrical, those on main stem larger than those on branches, distant on lower and middle portions, contiguous on distal portions of stems and branches, slightly deflected, ovate or ovate-oblong, 2.0–3.5 × 0.8–2.0 mm, margin denticulate, rounded at base, with acroscopic base enlarged, not or slightly overlapping stems and branches, apex acute; strobili solitary or pairs, terminal on the branches, compact, dorsiventrally complanate, 3.0–5.0 × 1.8–2.5 mm; sporophylls strongly dimorphic, resupinate (i. e. the smaller sporophylls in the ventral plane); dorsal sporophylls ovate-lanceolate, 1.1–1.8 × 0.3–0.5 mm base rounded, apex acute, margin denticulate, with the sporophyll-pteryx complete and denticulate; ventral sporophylls ovate-lanceolate, 0.8–1.2 × 0.3–0.6 mm, obviously carinate, base rounded, apex long acuminate, margin denticulate; megasporangia borne in basal portion of strobilus on lower side; megaspores pinkish to reddish-brown, subglobose, 220–280 μm in diam., surface papillate; microspores pale yellow, tetrahedral-globose, 24–32 μm in diam., surface verrucate with dense honeycomb-like microsculpture.

Distribution and habitat.

Selaginella dushanensis is currently known only from the type locality: Jia Feng Yan Forest in Dushan County, south-eastern Guizhou. The species occurs on wet rocks in montane evergreen broadleaved forest, along a perennial stream at elevations of 700–800 m.

Etymology.

The specific epithet dushanensis is derived Dushan County, south-eastern Guizhou, where the new species was first discovered.

Conservation status.

Currently, the only known population of Selaginella dushanensis is located in Dushan, Guizhou. The individuals are scattered along a stream bank for a distant of ca. 500 metres. We estimate that there are more populations of this species existing in south-eastern Guizhou and adjacent regions, which are to be discovered in the future. The exact population size and distribution range remain unclear. We provisionally assess its conservation status as Data Deficient (DD) according to IUCN Red List Categories and Criteria (IUCN 2024).