Ophioglossum isanense S. Petchsri, Li-Bing Zhang & T. Jaruwattanaphan 2022, sp. nov.
Creators: name: Petchsri, Sahanat
name: Zhang, Li-Bing
name: Jaruwattanaphan, Tassanai
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Polypodiopsida
Ophioglossales
Ophioglossaceae
Ophioglossum
Ophioglossum isanense

description: Ophioglossum isanense S. Petchsri, Li-Bing Zhang & T. Jaruwattanaphan, sp. nov.
(Figs. 2 & 3, Table 1).
Type:— THAILAND. Sakon Nakhon Province: Phu Phan National Park, 17°03.45’N 103°58.20’E, ca. 500 m, 21 July 2017, S. Petchsri & M. Kidyoo 2017-07 (holotype BCU!; isotypes BKF!, QBG!).
Diagnosis:— Similar to Ophioglossum jaykrishnae Patil et al. (2020: 240) in having colored trophophylls and spike stalks when young, but differs in smaller size, cylindrical rhizomes (vs. tuberose to subglobose), the presence of persistent leaf sheath at top of rhizome, elliptic or lanceolate leaf shape, common stalk and abaxial side of trophophylls brownish green (vs. brownish pink throughout) and exine surface psilate with scattered microperforation (vs. tubereulate-varicose).
Terrestrial, 1.5–6.5 cm in height. Rhizome cylindrical, 0.2–0.4 cm tall, 1 mm in diameter, bearing 1–2 stoloniferous roots, to 3.5 cm long. Common stalk or phyllophore 1–2.5 cm long, terranean-subterranean, white when subterranean, brownish-green when terranean, glabrous, covered with persistent, brown leaf sheath at base. Trophophylls 1–2(–3) on a rhizome; elliptic or elliptic–lanceolate, entire, acute at apex, narrowly cuneate at sessile base, 0.5–2 cm long, 0.7–1.5 cm broad, green on upper side, green or green-brownish on lower side; costae not distinct; veins anastomosing, areoles hardly visible, often with many included free veinlets in many smaller areoles; texture softly herbaceous, rather fleshy, glabrous; fertile segment simple, with fertile stalks of 1.8–3.0 cm long, inserted on adaxial side at trophophyll lamina base, brownish at lower portion; strobili or fertile spike 0.5–1.0 cm long, ending with minute sterile tip. Sporangia up to 0.5 mm in diameter; 4–10 on either side, globose, embedded. Spores trilete, equatorial diameter 16–28 μm; globose to triangular-globose in polar view; arms distinctly raised, ridged, joined up to the middle of proximal pole and extending up to margins; ornamentation coarsely microrugulate to microreticulate on distal face, psilate with scattered micro perforation on proximal face (Figs. 2G–H).
Distribution: —The new species is found growing naturally in the NE, and SE regions of Thailand (Figure 4).
Ecology: —On sandy soil in open areas of mixed deciduous forest on a sandstone plateau at an elevation of ca. 300–500 m (Figs. 2A–B) or terrestrial in seasonal swamp area at low altitude.
Etymology: —The species epithet “ isanense ” refers to the Northeast Thailand or Isan where the species was found.
Conservation status: — Ophioglossum isanense is assessed here as Near Threatened (NT) following the IUCN Criteria (2019). It is known only from four natural sites. The first site is the type locality, Phu Phan National Park, with an estimated area of occupancy around 1 km 2. It is a small population, comprising about 100 individuals. The second site is Phu Pha Lek National Park, located in Sakon Nakhon Province also with as small a population as the type locality. The third site is Pha Nam Thip Wildlife Sanctuary, Roi Et Province, comprising a small population of less than 100 individuals. The last known site is a seasonal swamp area at Watthana Nakhon District, Sa Kaeo Province. This area might be disturbed by non-timber forest products gathering activities and this could affect the survival chances of this species.
Additional specimens examined (paratypes):— THAILAND. Sa Kaeo: Watthana Nakhon, Ban Phrao Community Forest, 60 m elev., 5 Dec 2018, S. Petchsri & C. Rattamanee 2017-30 (BCU!); Sakon Nakhon: Phu Phan National Park, 15 July 2017, T. Jaruwattanaphan, K. Sripathomkul & S. Longchuphon 20150715-8 (QBG!); Sakon Nakhon: Phu Phan National Park, 17 Aug 2020, T. Jaruwattanaphan, P. Limpanasittichai & S. Chokrussamehirun 200817-1 (QBG!); Sakon Nakhon: Phu Pha Lek National Park, 498 m elev., 16 Aug 2020, T. Jaruwattanaphan, P. Limpanasittichai & S. Chokrussamehirun 200816-4 (QBG!); Roi Et: Tum Pha Nam Thip Wildlife Sanctuary, 336 m elev., 15 Aug 2020, T. Jaruwattanaphan, P. Limpanasittichai & S. Chokrussamehirun 200815-7 (QBG!).
Taxonomic notes: —Because of the trophophyll colors, Ophioglossum isanense resembles O. thermale Komarov (1914: 85) sensu Kachhiyapatel et al. (2018) reported from Gujarat state, India, but the presence of brown persistent leaf sheath (Table 1) and molecular results (Fig. 1) indicated the distinctness of the new species from O. thermale. Ophiglossum isanense was previously labeled as O. cf. nudicaule Linnaeus f. (1781: 443) in our previous phylogenetic study (Zhang et al. 2020) due to its small size, but our molecular results confirm that these two species are different from each other. In addition, the type of O. nudicaule is Thunberg s.n.; South Africa: Cape of Good Hope (UPS-25286). In the tree, “ O. cf. nudicaule ” is an undescribed species awaiting more study. Although no topotypes of O. nudicaule from South Africa have yet been sampled in any molecular study, we believe they would go with “ O. nudicaule ” in the tree.
1 based on Patil et al. 2018, 2 based on Patil et al. 2020, 3 based on Kachhiyapatel et al. 2018.
Ophioglossum isanense also has the same size range as O. gujaratense Patil et al. (2018: 274–275) and O. jaykrishnae, the recently discovered member of Ophioglossum from Gujarat state, India. However, O. isanense strongly differs from O. gujaratense in rhizome shape, ornamentation on exine of spores and the number, color, shape, texture, angle to fertile stalk and size of trophophylls (Table 1). This is a consistent result with the molecular phylogeny (Fig. 1) of Zhang et al. (2020). Furthermore, O. isanense differs from O. jaykrishnae by its smaller size, rhizome shape, the presence of persistent leaf sheath at top of rhizome and ornamentation on exine of spores (Table 1).
description: Published as part of Petchsri, Sahanat, Zhang, Li-Bing & Jaruwattanaphan, Tassanai, 2022, Ophioglossum isanense sp. nov. (Ophioglossaceae, Pteridophyta) from Thailand, pp. 158-164 in Phytotaxa 533 (3) on pages 159-163, DOI: 10.11646/phytotaxa.533.3.1, http://zenodo.org/record/6048423