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Research Article
Sindora stipitata (Detarioideae, Leguminosae), a new species from Thailand
expand article infoWilawan Promprom, Wannachai Chatan, Peerapon Saisaard§
‡ Mahasarakham University, Mahasarakham, Thailand
§ Unaffiliated, Surin Province, Thailand
Open Access

Abstract

Sindora stipitata, a new species in the subfamily Detarioideae (Leguminosae), collected from Nakhon Phanom Province, Thailand, is described and illustrated. The new species is morphologically similar to S. leiocarpa but differs in its smaller stature (3–5 m high), 6-foliolate paripinnate leaves, falcate persistent stipules, presence of a petal auricle, absence of a petal claw, stipitate ovary and capitate stigma. A key to the Thailand and Malesia species of Sindora is provided.

Keywords

Sindora , Fabaceae , Nakhon Phanom Province, plant diversity, Thailand, taxonomy

Introduction

Sindora Miq. is a genus in the tribe Detarieae (Detarioideae: Leguminosae) (McKinder 2005). It consists of 18–20 species distributed in Southeast Asia, one in Africa (Larsen et al. 1984, Lock and Heald 1994, McKinder 2005), two species in the South Asia (Kumar and Sane 2003) and two species in China (Chen et al. 2010). Three species have been identified in Thailand. Of these, S. siamensis Teysmann ex Miq. is a very common species of dry deciduous dipterocarp forests and beach forests, especially the type variety (Larsen et al. 1984).

During floristic surveys in the years 2009 to 2016 in the northeast of Thailand, a specimen of Sindora was collected from the Phulangka National Park in Nakhon Phanom Province which, on further investigation, was found to be clearly different from the previously reported species. It closely resembled S. leiocarpa Backer ex de Wit from Malesia. This was confirmed after comparing it against the type and description of S. leiocarpa and is here described as a new species.

Materials and methods

Morphological characters were studied based on living plants observed during a field trip in the northeast of Thailand in the years 2009 to 2016 and from dried herbarium specimens housed in BKF and K. The studies consulted all relevant taxonomic literature in Thailand and neighbouring countries. Measurements were made using a vernier caliper and were examined under a stereo dissecting microscope. The conservation status of the new species was evaluated based on the guidelines of the International Union for Conservation of Nature (IUCN 2017).

Taxonomy

Sindora stipitata Chatan & Promprom, sp. nov.

Figs 1, 2

Diagnosis

Sindora stipitata is very similar to S. leiocarpa from Malesia, but it is easily distinguished by the following characters: a smaller stature (3-5 m high), 6-foliolate paripinnate leaves, falcate persistent stipules, presence of a petal auricle, absence of a petal claw, stipitate ovary and capitate stigma.

Figure 1. 

Sindora stipitata. A habit and habitat B branches and inflorescences C branch with leaves and stipules D branch with fruits. Photographs of the type specimen by W. Chatan.

Figure 2. 

Line drawing of Sindora stipitata Chatan & Promprom, sp. nov. A a branch with leaves and inflorescence B floral bud C floret D posterior sepal (abaxial side) E posterior sepal (adaxial side) F one of the remaining narrower sepal (abaxial side) G one of the remaining narrower sepal (adaxial side) H petal (adaxial side) I free staminode J fused stamen K pistil. Illustration by W. Chatan (based on type specimen).

Type

THAILAND. Nakhon Phanom Province: Phu Langka National Park, elevation 250–350 m, 17°59'18.7"N 104°07'50.1"E (Fig. 3), 20 April 2012, W. Chatan 1231 (Holotype: BKF!; Isotype: K!).

Figure 3. 

Distribution of Sindora stipitata Chatan & Promprom (*) in Phu Langka National Park, Nakhon Phanom Province, Thailand.

Description

Small tree, 3–5 m high. Stem diameter 3–5 cm. Stipules falcate, 23–25 × 1.0–1.3 mm, coriaceous, glabrous on both surfaces, persistent, venation distinctly reticulate. Leaves 6-foliolate, paripinnate, leaflets opposite; petioles 3.0–5.5 cm long, with sparse minute hairs or glabrescent; rachis 7–11 cm long, with sparse minute hairs or glabrescent. Leaflets rigidly coriaceous, elliptic or ovate or obovate or oblong, 7.5–11.5 × 3.5–5.3 cm; apex obtuse or sometime shallowly emarginate; base obtuse or cuneate, slightly asymmetric, glabrous on both surfaces, sometimes with a few minute hairs on the blade margin; abaxial side dull. Petiolules 3–6 mm long; glabrescent or with sparse minute hairs. Inflorescences paniculate, lax, up to 20 cm long, lateral branches up to 6 cm long, both rachises and lateral braches densely pubescent; bracts and bracteoles ca. 4.5 × 1.5 mm, puberulous; pedicels 11–12 mm long, densely puberulous. Buds ca. 15 × 10 mm, elliptic. Pedicel 10–11 mm long, densely puberulous. Hypanthium asymmetrically short and funnel-like, 0.5–1.0 mm long, brownish-yellow. Calyx lobes 4, thick, brownish-yellow, without any spiny outgrowth on the outer surface, densely puberulous outside, appressed hairs inside; the posterior lobe boat-shaped and obovate, 14–20 × 10–11 mm, apices acuminate; the other three lobes narrower, 15–20 × 4–6 mm, narrowly oblong or elliptic, apices narrowly acute. Corolla comprised of a solitary boat–shaped petal, lanceolate or narrowly obovate, thick, 15–17 × 5–6 mm, apices acute or acuminate, bases auriculate, puberulous outside, glabrous inside. Stamens 10, dorsifixed; upper stamen free, staminodal, 10–11 mm long, lower 2/3 of filament length densely puberulous, upper 1/3 of filament length sparsely hairy and glabrous near apex; remaining nine stamens, fertile, joined at the base into a sheath; sheath ca. 8–9 × 4.0–4.5 mm, densely puberulous on both surfaces; the two largest stamens are fertile, free parts of filament ca. 22–25 mm, lower half of the free parts of filament sparsely hairy and the upper half glabrous; anthers 5.5–6.0 × 1.5–1.6 mm, glabrous; other fertile stamens seven, free parts of filament 7–8 mm, lower 1/3 of the free parts densely puberulous, upper 2/3 of the free parts sparsely hairy and glabrous near apex; anthers, 2.5–3.0 × 1.0–1.2 mm, glabrous. Pistils with 5–6 mm stipe length; stipes densely puberulous; ovary asymmetrically elliptic; 7–8 × 4.5–5.0 mm, densely puberulous, no spiny outgrowth; style 9–11 mm long, densely puberulous on lower parts and sparsely hairy on the anterior side of upper parts; stigma capitate, glabrous. Pods circular or ellipsoid to obovate, 3.3–9.0 × 3.5–5.5 cm diameter, flattened, slightly smooth, unarmed, obscurely veined, with 1.5–5.0 mm long beaks, sparsely hairy on both surfaces, densely appressed hairs on the margin; seeds 1–4.

Other specimen examined

THAILAND. Nakhon Phanom Province: Phu Langka National Park, 29 June 2013, fruiting, P. Saisaard 55 (BKF).

Flowering and fruiting

Flowering in March–May and fruiting April–June.

Distribution

The new species is a Thai endemic and is known from only the type locality in the Phulangka National Park, Ban Pheang District, Nakhon Phanom Province, North-eastern Thailand.

Ecology

This new species grows in open areas of dry deciduous forest at an elevation of 250–350 m.

Vernacular name

Ma Kha Tae Nakhon Phanom, Mak Tae.

Etymology

The specific epithet refers to its distinctly long ovary stipe. This character is one of many morphological characters that distinguishes the new species from its closely related species.

Preliminary conservation status

Sindora stipitata is known only from the type locality and its estimated extent of occurrence is less than 100 km2. The number of mature individuals was less than 1,000 and the occupied area is continuing to decline slightly. Therefore, it should be considered as “Critically Endangered” according to the IUCN criteria B1 (IUCN 2017).

Discussion

Sindora stipitata is closely related to S. leiocarpa, a plant that grows in Sumatra (Jimbi, Palembang and Riau) and Borneo (Sarawak, Brunei, Sabah and Kalimantan) (Hou 2000), but is easily distinguished from the latter by several morphological characters. Details of the differences between S. stipitata and S. leiocarpa are presented in Table 1.

The new species is also related to S. coriacea (Baker) Prain. Both have unarmed sepals, but S. stipitata is clearly different from S. coriacea by its stature of a small tree (3–5 m high) (vs. a large tree up to 50 m high), its abaxial leaflet surface dull brown (vs. shining), the two largest stamen 22–25 mm long (vs. ca. 10 mm long) and anthers 5.5–6 mm long (vs. 2–3 mm long). The new species also clearly differs from S. laotica Gagnep., a species that is distributed near the border of Thailand (in Vientiane, Phou Khao Khouay National Biodiversity Conservation Area, Lao) and Vietnam (Larsen, Larsen and Vidal 1980); the two species are different in that there is no spiny outgrowth on the outer surface of the calyx of the new species (vs. calyx spinescent). The following identification key for Sindora in Thailand and Malesia is constructed by modification of the key from the Flora Malesiana (Hou 2000).

Table 1.

Distinguishing features between S. stipitata Chatan & Promprom and S. leiocarpa de Wit.

Characters S. stipitata sp. nov. S. leiocarpa
1. Habit Small tree 3–5 m high, 3–5 cm diam. Large tree, 25–45 m high, 45–80 cm diam.
2. Stipule Falcate, 23–25 mm long Lancelate, 3–5 mm long, caducous
3. Leaflet size 7.5–11.5 × 3.5-5.3 cm 2.5–9.5 × 2–5 cm
4. Pedicel length 10–11 mm 1–1.5 mm
5. Sepal size 14–20 × 4-11 mm 2–6 × 2–3.5 mm
6. Petal length 15–17 mm 5–6 mm
7. Petal claw Absent Present at about the lower half
8. Petal auricle Present Absent
9. Staminal sheath 8–9 mm long (high) 2–3 mm long (high)
10. Free filament part length of united stamens 7–25 mm ca. 7 mm
11. Anther length of two largest stamens 22–25 mm 2–2.5 mm
12. Anther length of seven smallest fertile stamens 7–8 mm Up to 0.75 mm
13. Ovary stipe length 5–6 mm Subsessile or shortly stipitate (ca. 1 mm)
14. Ovary length 7–8 mm ca. 4.5 mm
15. Stigma Capitate Obscure

Key to Sindora Species in Thailand and Malesia

1 Leaflets minutely puberulous or pubescent on both surfaces S. siamensis
Leaflets glabrous on both surfaces or minutely puberulous or pubescent on the lower surface or rarely sparsely puberulous above 2
2 Leaflets glabrous on both surfaces 3
Leaflets only minutely puberulous or pubescent on the lower surface or rarely sparsely puberulous above 8
3 Apex of leaflet obtuse, rounded, retuse or emarginate 4
Apex of leaflets acute to acuminate 6
4 Calyx lobes densely spinescent S. supa
Calyx lobes smooth, unarmed 5
5 Petal auricle present, petal claw absent, ovary stipe 5-6 mm long S. stipitata
Petal auricle absent, petal claw present, ovary subsessile or shortly stipitate S. leiocarpa
6 Midrib on the lower surface of the leaflet without a gland near the tip S. inermis
Midrib on the lower surface of the leaflet with a gland near the tip 7
7 Midrib narrow and shallowly grooved on the upper surface S. coriacea
Midrib slightly prominent on upper surface S. galedupa
8 Fertile stamens 9, the uppermost staminode absent S. javanica
Fertile stamens and staminodes 10, the uppermost staminode present 9
9 Calyx lobes with spinescent outgrowths or warts 10
Calyx lobes smooth, unarmed 13
10 Leaves 3-jugate 11
Leaves 4- or 5-jugate 12
11 Leaflets with apex acute or acuminate S. sumatrana
Leaflets with apex obtuse, the tip slightly notched S. echinocalyx
12 Calyx with spiny outgrowth mostly at the upper half S. wallichii
Calyx with loosely, irregularly, minute, spiny outgrowth outside S. affinis
13 Leaflets 3- or 4-jugate. Petals hairy on the longitudinal, central part S. beccariana
Leaflets often 5- or 6-jugate. Petal glabous inside 14
14 Ovary glabous in the longitudinal, central part S. bruggemanii
Ovary all densely woolly 15
15 Abaxial side of leaflet usually densely hirsute S. velutina
Abaxial side of leaflet sparsely and minutely puberulous S. irpicina

Acknowledgements

The authors are indebted to the curators and officers of L for providing information on the type specimens investigated in this study. We would like to thank Mr. Teerawut Namsawang, Mr. Nopphanun Kanithaisong and the officers in Phulangka National Park while collecting plant specimens during field trips. Thanks for linguistic advice from Dr. Jolyon Dodgson, Faculty of Science, Mahasarakham University. This research was financially supported by Mahasarakham University.

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