Panax siamensis J. Wen, 2023

Wen, Jun, Krupnick, Gary & Esser, Hans-Joachim, 2023, Panax siamensis J. Wen, a new species of the ginseng genus (Panax, Araliaceae) from northern Thailand, PhytoKeys 234, pp. 51-59 : 51

Panax siamensis J. Wen sp. nov.

Figs 1 , 2

Type.

Thailand. Chiang Mai. A southerly ridge of Doi Pa Mawn, an easterly spur of Doi Angka (i.e., Doi Inthanon), ca. 1350 m, berries bright red with a black top, 30 Dec 1926, in fr, H. B. G. Garrett 364 (holotype: BKF!; isotypes: ABD!, C!, E!, K!, TCD!) .

Diagnosis.

Rhizomes horizontally elongated with thick internodes. Leaves 3-5 at the tip of stem, exstipulate, with 7-9 leaflets; leaflets sessile or nearly so, tapering toward the base, lanceolate, long acuminate at apex, long acute at base, serrulate to doubly so at margin, membranaceous, bristly along veins and veinlets on both surfaces. Ovary 2-locular. Fruits subglobose, bright red with a black top, persistent stigmas recurved, 1-2 seeded, 5-6 mm long, 7-8 mm wide, 3-3.5 mm thick. Seeds ovate, 5-5.5 mm long, 3-4 mm wide, 2.5-3.5 mm thick, surface rough.

Description.

Perennial herb, 60-70 cm, hermaphrodite. Rhizomes horizontally elongated with thick internodes, brown outside, whitish inside; stems light green, 30-45 cm. Leaves 3-5 at the tip of the stem, with 7-9 leaflets, exstipulate, petioles 7-11 cm, glabrous; leaflets sessile or nearly so, tapering toward the base, lanceolate, basal leaflets 7-10 cm long, 2-2.5 cm wide, upper leaflets 13-17.5 cm long, 2-3 cm wide, long acuminate at apex, long acute at base, serrulate to doubly so at margin, membranaceous, bristly along veins and veinlets on both surfaces, bristles or setae 1-2.5 mm long, lateral veins 17-25 per side. Inflorescence consisting of a terminal umbel, sometimes with 1-2 lateral umbels, peduncle 15-20 cm, glabrous, terminal umbels with 70-90 flowers, lateral umbels with 20-30 flowers; pedicels puberulent to slightly so, pale light green, with dark violet color at both ends at late flowering to fruiting stage, 10-13 mm in terminal umbels, 6-8 mm in lateral umbels; bracteoles lanceolate, membranaceous, glabrous, 1.3-1.6 mm long, 0.2-0.3 mm wide, mostly not persistent at fruiting stage. Sepals 5, triangular, 0.4-0.5 mm long, 0.6-0.7 mm wide; petals light green, 1.6-2 mm long, 1-1.1 mm wide; anthers white, filaments pale light green, 2-2.2 mm; ovary 2-locular, stigma white. Fruits subglobose, bright red with a black top, persistent stigmas recurved, 1-2 seeded, 5-6 mm long, 7-8 mm wide, 3-3.5 mm thick. Seeds ovate, 5-5.5 mm long, 3-4 mm wide, 2.5-3.5 mm thick, surface rough.

Additional specimens examined.

Thailand. Chiang Mai: Mae Soi Ridge, Mae Soi Subdistrict, near Ban Bah Cluary ( Meo Village ), 1475 m, 11 Aug 1991, in fl, shaded place, mixed evergreen hardwood and pine forest, J. F. Maxwell 91-722 (A, CMUB, E); Ob Luang National Park , Mae Soi Conservation Area , Bah Gluay (Hmong) village area, between the Ranger Station and the village, on the N side of the road passing through the Bah Gluay village , elev. 1550 m, evergreen forest, plant c. 60-70 m tall, fruits red with a black top, 04 Nov 2003, fr, J. Wen 7371 (KUN, US).

Phenology.

Flowering in August; fruiting in November to December.

Distribution.

Northern Thailand; elevation 1350-1550 m.

Ecology.

In shaded areas of monsoon evergreen hardwood forests, or in mixed evergreen hardwood and pine forests, granite bedrock.

Etymology.

The species epithet denotes the geographic distribution of the species in Thailand.

Conservation

The area of occupancy (AOO) of this species as measured with a 2 × 2 grid is estimated to be 12 km2; the extent of occurrence (EOO) is estimated to be 39.54 km2. Apart from habitat destruction, no specific threats are known. It is not found in cultivation, and it is not known from any ex situ collections. With a restricted area of occupancy, only three known locations, and a plausible future threat due to stochastic events or habitat disturbance brought about by human activities near villages, Panax siamensis is preliminarily assessed with a status of Vulnerable (VU D2) according to IUCN Red List Criteria ( IUCN 2012, 2022).

Figures

Figure 1. Illustration of Panax siamensis J. Wen based on J. Wen 7371 (US) A habit B horizontal rhizome with base of stem C leaflet margin D leaflet abaxial surface E infructescence F enlarged infructescence G bracteoles subtending pedicels at flowering stage H older flowers after petals falling off, showing 2 - locular ovary I young fruiting stage J seed K seed surface.

Figure 2. Field images of Panax siamensis and its habitat A habitat in monsoon evergreen forest B infructescence showing red fruits with a black top C habit. Photo credit: A (Ricky Ward), B, C (Jun Wen).