Didiclis chiangdaoensis X.M. Zhou, Yu P. Hu & Chantanaorr., 2025
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publication ID |
https://doi.org/10.11646/phytotaxa.705.2.9 |
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DOI |
https://doi.org/10.5281/zenodo.16719957 |
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persistent identifier |
https://treatment.plazi.org/id/03A70C3A-E139-FF9D-A7E2-FD898239F809 |
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treatment provided by |
Felipe |
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scientific name |
Didiclis chiangdaoensis X.M. Zhou, Yu P. Hu & Chantanaorr. |
| status |
sp. nov. |
Didiclis chiangdaoensis X.M. Zhou, Yu P. Hu & Chantanaorr. , sp. nov. ( Figs. 1–3 View FIGURE 1 View FIGURE 2 View FIGURE 3 ).
Type:— THAILAND. Chiang Mai Province: Doi Chiang Dao Wildlife Sanctuary, Doi Chiang Dao Summit , elev. ca. 2200 m, 19.397 656 N, 98.889 145 E, under the limestone, 10 October 2019, Xin-Mao Zhou, Sahut Chantanaorrapint & Orawanya Suwanmala 1356 (holotype: PYU!; Isotypes: BCU!, BKF!, PSU!) .
Diagnosis: — Didiclis chiangdaoensis is partly similar to other species in the Bisulcata group in having resupinate strobili, dimorphic sporophylls, and obovate dorsal leaves. However, this species is characterized by its extremely small plants (<10 cm) (vs. over 20 cm in other species of the Bisulcata group) and entire margins of sterile leaves (vs. denticulate or ciliolate margins of sterile leaves in other species of the Bisulcata group).
Plants terrestrial, creeping to ascending, 3–10 cm ( Figs. 2A, B View FIGURE 2 ; 3 View FIGURE 3 ). Rhizophores borne from base to upper part of main stem, on ventral side in axils of branches, 1.0–2.0 cm, 0.1–0.3 mm in diam., stramineous, roots much forked ( Fig. 3 View FIGURE 3 ). Main stems branched from near base upward, pinnately branched, stramineous, main stem 0.4–0.8 mm in diam. ( Fig. 3 View FIGURE 3 ), with one vascular bundle, subquadrangular, sulcate, not zigzag, glabrous, primary leafy branches 1–6 pairs, 1–3 times pinnately branched, branchlets sparse to dense, adjacent primary branches on main stem 0.5–2.0 cm apart, leafy portion of main stem including leaves 3.2–6.0 mm wide at middle ( Fig. 3 View FIGURE 3 ), ultimate branches 3.0– 6.5 mm wide including leaves ( Figs. 2C, D, E, F View FIGURE 2 ; 3 View FIGURE 3 ). Sterile leave not white-margined, margins entire ( Fig. 1A, B, C, D View FIGURE 1 ). Axillary leaves on branches symmetrical, elliptic, 2.0–2.6 × 0.9–1.2 mm, base exauriculate, cuneate to rounded, apex obtuse ( Figs. 1D View FIGURE 1 ; 2D, F View FIGURE 2 ); these on stem oblong-ovate, base rounded, 1.7–2.9 × 1.0– 1.5 mm ( Fig. 1C View FIGURE 1 ). Dorsal leaves approximate, nearly symmetrical, those on main stem not obviously larger than those on branches ( Figs. 1B View FIGURE 1 , 2C View FIGURE 2 ; 3 View FIGURE 3 ); dorsal leaves on branches 1.3–1.9 × 0.6–0.9 mm, carinate, base cordate, oblique, apex aristate, up to 1/5–1/4 as long as leaf, 0.1–0.2 mm ( Fig. 2C, E, G View FIGURE 2 ). Ventral leaves asymmetrical, those on main stem not obviously larger than those on branches ( Figs. 1A View FIGURE 1 ; 3 View FIGURE 3 ); ventral leaves on branches distant, spreading or slightly deflexed, oblong or oblong-ovate, 2.4–2.8 × 1.2–1.4 mm, apex slightly acute; acroscopic base slightly enlarged, not or slightly overlapping stem and branches ( Figs. 2C, E, G View FIGURE 2 ; 3 View FIGURE 3 ). Strobili solitary, terminal, complanate, resupinate, 2.6–4.5 × 3.4–4.7 mm ( Figs. 1E, F View FIGURE 1 ; 2D, F View FIGURE 2 ; 3 View FIGURE 3 ); sporophylls strongly dimorphic; dorsal sporophylls oblong-falcate, apex acuminate to apiculate, with sporophyll-pteryx nearly complete and denticulate ( Fig. 1G View FIGURE 1 ); ventral sporophylls ovate, apex acuminate to aristate, with sporophyll-pteryx complete and minutely denticulate; carinate or not, margin entire, very minutely denticulate in upper portion of margins, elsewhere entire or subentire ( Fig. 1H View FIGURE 1 ); megasporangia in basal portion on lower side of strobili; microsporangia orbicular. Microspores pale yellow, hemispherical, 31.1–41.8 um, laesurae extend to the equator, surfaces covered with small papillae or verrucae with fused spines ( Fig. 1L, M, N View FIGURE 1 ). Megaspores dark brown, spheroidal, 385–477 um, laesurae equal to radius, perispore smooth and densely covered with snowy verrucous composed by honeycombed ornamentation ( Fig. 1I, J, K View FIGURE 1 ).
Geographical distribution:— Didiclis chiangdaoensis is currently only found in limestone area, subalpine forest, Doi Chiang Dao summit, Chiang Mai Province, and may represent an endemic species of northern Thailand.
IUCN Red List category:—This species is only known from its type locality along the walking trail of a tourist site. Only one population, consisting of fewer than 20 individuals, was found. Two field trips were carried out in this area by the authors in 2018 and 2019, respectively, but only one population was discovered. We believe that tourist activities in this region threat the survival of the species. We here assess this species as Critically Endangered (CR) according to the IUCN criteria (2024).
Etymology: — The epithet “ chiangdao ” refers to Doi Chiang Dao Wildlife Sanctuary and Biosphere Reserve, Chiang Mai Province, Thailand, where the new species was discovered. The Latin suffix “ -ensis ” refers to its geographical origin.
Add Additional specimens examined:— THAILAND. Chiang Mai Province: Doi Chiang Dao Wildlife Sanctuary, Doi Chiang Dao summit, elev. ca. 2200 m, 19.397 656 N, 98.889 145 E, 9 October 2019, Sahut Chantanaorrapint & Orawanya Suwanmala 3933 (PSU).
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.