Distinct from A. tipuliferus I.M.Turner & Utteridge (Fig. 2C, D), the only other Artabotrys species in Thailand with linear petals, by its relatively long flower pedicels (8–16 mm long vs. 2–4 mm long) and sessile (vs. stipitate) monocarps. Similar to A. multiflorus C.E.C.Fisch. (Fig. 2E, F) but distinguished by its chartaceous (vs. coriaceous) leaves, acute (vs. obtuse to acute) petal apex and linear (vs. narrowly lanceolate) petals, specifically its longer and narrower outer petals (35–45 mm long, blade 1–2 mm wide vs. 18–30 mm long, blade 3–5 mm wide) and inner petals (32–40 mm long, blade 1–1.5 mm wide vs. 18–27 mm long, blade 2–4 mm wide).

Figure 2. 

A, B Artabotrys longipetalus sp. nov. A habit and inflorescence (T. Insura 57) B flowers, showing linear petals with acute apex (T. Insura 57) C, D Artabotrys tipuliferus C flowers, showing short flower pedicel and linear petals (S. Phusomsaeng 272) D fruit, showing short fruit pedicel and stipitate monocarps (T. Insura 56) E, F Artabotrys multiflorus E flowers, showing lanceolate petals with acute to obtuse apex F hooked inflorescence with many flowers. Photos: A, B, D T. Insura C Royal Botanic Garden Edinburgh E, F P. Chalermglin.

Peninsular Thailand. Surat Thani Province: Ban Na San District, Tai Rom Yen National Park, Dat Fa Waterfall, 730 m elev., 25 February 2006, S. Gardner ST2374 (holotype: BKF [SN 198209]; isotypes: BKF [SN 198210], QBG [SN 49402]).

Climbers, to ca. 10 m tall. Twigs drying light brown to brownish black, glabrous, epidermis non-flaky. Leaf laminas 8.5–15 cm long, 2.9–7.7 cm wide, elliptic to oblong-elliptic, chartaceous, glabrous above and below; base cuneate or decurrent on petiole; apex acute to acuminate, acumen up to 5 mm long; midrib raised to flush above, prominent below; secondary veins 7–12 pairs per leaf, raised to flush above and below; tertiary venation reticulate, visible on both surfaces; petiole 2–8 mm long, 1–1.5 mm in diameter, glabrous. Inflorescences 1–15-flowered, peduncles recurved (often laterally compressed and hook-like), glabrous, lateral branches condensed, pedicels 8–16 mm long, ca. 1 mm in diameter, subglabrous. Sepals 3, free, valvate, ca. 1.5 mm long, 1.5–2 mm wide, ovate, glabrous inside, sparsely puberulent outside, apex acute, green in vivo. Petals 6, free, valvate, sparsely appressed-pubescent to glabrous on both surfaces except the glabrous base inside, membranous, greenish yellow in vivo, blade often curly, base concave. Outer petals 3, 35–45 mm long, claw 2–2.5 mm wide, blade 1–2 mm wide, linear, apex acute. Inner petals 3, 32–40 mm long, claw 1.5–2 mm wide, blade 1–1.5 mm wide, linear, apex acute. Stamens 25–35, ca. 1 mm long, ca. 1 mm wide, oblong, anther connective apex truncate. Carpels 8–10, ovary ca. 1 mm long, ca. 0.5 mm wide, stigma ca. 0.5 mm long, cylindrical. Fruit of up to 8 monocarps borne on a glabrous pedicel 19–22 mm long, ca. 4 mm in diameter. Monocarps ca. 26 mm long, 18–20 mm wide, broadly ellipsoid, rough, glabrous, apex weakly beaked (ca. 1 mm long) or rounded, sessile, colour in vivo unknown, drying brownish black, pericarp thickness unknown. Seeds not seen.

Flowering specimens collected in February and August; fruiting specimens collected in May.

So far only known from peninsular Thailand (Fig. 6). It occurs in lowland rain forests at elevation 100–730 m, in both undisturbed and partially disturbed sites, sometimes along ridges.

Etymology. The specific epithet reflects the long petals of this species.

Artabotrys longipetalus is only known from three localities, with estimated EOO and AOO of 1,165 km² and 12 km², respectively. All the localities are well within the boundaries of various National Parks in Thailand. Nevertheless, this species may become threatened with future climate change and/or other unpredictable threats owing to its restricted AOO and few known locations. Therefore, we suggest a status of Vulnerable [VU D2].

Peninsular Thailand. Nakhon Si Thammarat Province: Lan Saka District, Khao Luang National Park, Karom Waterfall, 100 m elev., 11 August 2006, T. Insura 57 (BKF). Surat Thani Province: Vibhavadi District, Kaeng Krung National Park, ridge ca. 2 km east of Ban Cham village, 200 m elev., 13 May 2006, S. Gardner & P. Sidisunthorn ST2731 (BKF).

Artabotrys longipetalus is similar to A. multiflorus from Myanmar (Dawna Range) and Thailand (Kanchanaburi and Tak) in having long, narrow petals and sessile monocarps with rounded to weakly beaked apex. Also comparable to the new species, A. arachnoides J.Sinclair from New Guinea shares a similar floral morphology of long, linear, curly petals and long flower pedicels but differs in its highly coriaceous leaves, larger sepals (4–5 mm long) and larger petals (50–60 mm long, 2–3 mm wide). A number of Artabotrys species also possess linear petals but have very short flower pedicels (2–4 mm long): A. speciosus Kurz from the Andaman Islands, A. sumatranus Miq. from Sumatra, Java and Borneo (Kalimantan), and A. tipuliferus from peninsular Thailand and Peninsular Malaysia. Significantly, A. longipetalus was previously confused with A. sumatranus in Insura (2009). “Artabotrys sumatranus” in Insura (2009) consists of mixed elements: the description and line drawing of the vegetative parts and flowers match A. longipetalus whereas the description and line drawing of the fruit match A. tipuliferus. Apart from the short flower pedicels, A. tipuliferus can be further distinguished from the new species by its apiculate anther connective apex and the presence of a monocarp stipe (ca. 1 cm long) whereas A. sumatranus is distinct from the new species in having shorter petals (up to 15 mm long) and apiculate anther connective apex.

Distinct from other Artabotrys species in Thailand in having oblique leaf base and erect-pubescent lower leaf surface. Similar to A. uniflorus Craib (Fig. 4D–F) but with oblique (vs. rounded or rarely cuneate) leaf base, flat (vs. three-angled) petal blades, apiculate (vs. truncate) anther connective apex and short-stipitate (vs. sessile) monocarps that are weakly beaked (beak ca. 1 mm long vs. 2–5 mm long).

Peninsular Thailand. Surat Thani Province: Vibhavadi District, Khlong Yan Wildlife Sanctuary, trail from headquarters, ca. 200 m elev., 31 August 2002, D.J. Middleton et al. 1487 (holotype: BKF [SN 142020]; isotype: A).

Figure 3. 

Artabotrys insurae sp. nov. A habit and leaves, showing caudate to acuminate leaf apex (C. Leeratiwong 18-1522) B oblique leaf base and inflorescence with hooked peduncle (C. Leeratiwong 18-1522) C flower, showing oblong-ovate outer petals and oblong-elliptic inner petals (C. Leeratiwong 18-1522) D fruit (C. Leeratiwong 17-1116). Photos: C. Leeratiwong.

Climbers, to ca. 5 m tall. Twigs drying light brown to greyish black, sparsely to densely erect-pubescent, becoming glabrous, epidermis non-flaky. Leaf laminas 9–19 cm long, 3.7–7.5 cm wide, oblong-elliptic to oblong-obovate, chartaceous, glabrous above except the sparsely erect-pubescent midrib and secondary veins, sparsely to densely erect-pubescent below; base oblique; apex caudate to acuminate, acumen up to 15 mm long; midrib sunken above, prominent below; secondary veins 8–13 per side, sunken to flush above, raised below; tertiary venation reticulate, visible on both surfaces; petiole 3–10 mm long, 1–1.5 mm in diameter, erect-pubescent. Inflorescences 1-flowered (rarely 2-flowered), peduncles recurved (often laterally compressed and hook-like), sparsely erect-pubescent, lateral branches condensed, pedicels 5–15 mm long, ca. 1 mm in diameter, sparsely to densely erect-pubescent. Sepals 3, free, valvate, 6–10 mm long, 5–6 mm wide, ovate, sparsely puberulent inside, densely puberulent outside, apex acute, green in vivo. Petals 6, free, valvate, sparsely to densely puberulent on both surfaces except the glabrous base inside, chartaceous, yellow in vivo, blade flat, base concave. Outer petals 3, 17–29 mm long, claw 6–8 mm wide, blade 6–12 mm wide, oblong-ovate, apex acute. Inner petals 3, 16–28 mm long, claw 4–6 mm wide, blade 3–6 mm wide, oblong-elliptic, apex acute. Stamens 20–30, ca. 2 mm long, ca. 1 mm wide, oblong, anther connective apex apiculate. Carpels 10–14, ovary ca. 3 mm long, ca. 0.5 mm wide, stigma ca. 2 mm long, cylindrical. Fruit of up to 10 monocarps borne on a subglabrous pedicel 8.5–20 mm long, 2–2.5 mm in diameter. Monocarps 23–27 mm long, 10–13 mm wide, ellipsoid, smooth, glabrous, apex weakly beaked (ca. 1 mm long), base contracted into a stipe 1.5–4 mm long, green in vivo, drying brownish black, pericarp ca. 2 mm thick. Seeds 15.5–17.8 mm long, 9.4–10.7 mm wide, 4.6–5.2 mm thick, generally smooth with wrinkled area on sides, light yellowish brown.

Figure 4. 

A–C Artabotrys insurae sp. nov. A habit (T. Insura 58) B flower, showing flat petal blades (T. Insura 58) C fruit, showing weakly beaked monocarps with distinct stipes (D.J. Middleton et al. 1487) D–F Artabotrys uniflorus D habit E flower, showing three-angled petal blades F fruit, showing strongly beaked monocarps that are sessile. Photos: A, B T. Insura C D.M. Johnson D–F P. Chalermglin.

Flowering and fruiting specimens collected in August and September. Fruiting specimens also collected in February and June.

So far only known from peninsular Thailand (Fig. 6). It occurs in lowland moist and dry forests, secondary forests and forest edges at elevation 80–200 m.

The specific epithet was given in honour of Mr Tawee Insura, whose prolific collection of Artabotrys specimens during his MSc study led to the discovery of several new species and new records for Thailand.

Artabotrys insurae is estimated to have an EOO of 15,994 km² and an AOO of 20 km². This species largely occurs within various Wildlife Sanctuaries, which constitute Protected Areas in Thailand. A population exists in a remnant forest adjacent to Khao Le Buddhist Temple in Songkhla; such vegetation is regarded as sacrosanct and hence would likely remain undisturbed. We suggest a status of Vulnerable [VU D2] for this species because its restricted AOO makes it susceptible to future threats such as climate change.

Peninsular Thailand. Narathiwat Province: Sukhirin District, Hala-Bala Wildlife Sanctuary, 7 September 2006, T. Insura 75 (BK, BKF). Songkhla Province: Hat Yai District, Ton Nga Chang Wildlife Sanctuary, Puangpen et al. N192 (QBG); idem, Ton Nga Chang Waterfall, 150 m elev., 2 February 1997, C. Leeratiwong s.n. (PSU); idem, 80 m elev., 12 August 2006, T. Insura 58 (BK, BKF); Sadao District, Khao Le, 150 m elev., 16 August 2018, C. Leeratiwong 18-1522 (PSU); Sadao District, Ton Nga Chang Wildlife Sanctuary, Pha Dam Ranger Station, 350 m elev., 2 June 2017, C. Leeratiwong 17-1116 (PSU).

This species is most similar to A. uniflorus from peninsular Thailand (Chumphon, Ranong, Phang-Nga and Surat Thani) in having erect-pubescent lower leaf surfaces, 1-flowered (rarely 2-flowered) inflorescences, caudate to acuminate leaf apex and relatively narrow monocarps (10–15 mm wide). Its distribution overlaps with A. uniflorus in Surat Thani. Artabotrys siamensis Miq. from Northern, Northeastern, Eastern and Southwestern Thailand is also similar in having erect-pubescent lower leaf surfaces, but is distinct due to its coriaceous leaves, cuneate leaf base, thicker petals, numerous carpels (25–29 per flower), numerous monocarps (up to 22 per fruit) and broader monocarps (15–20 mm wide).

Peninsular Malaysia and peninsular Thailand (Fig. 6), in lowland rain forests.

Peninsular Thailand. Songkhla Province: Rattaphum District, Boripat Forest Park, 4 July 1986, J.F. Maxwell 86-444 (A) [A00571911]; idem, 6 April 2006, T. Insura 61 (BK, BKF). Satun Province: Thale Ban National Park, Ton Plio Falls, open area by stream, 115 m elev., 3 June 2001, R. Pooma et al. 2004 (BKF) [SN 134816]. Trang Province: Na Yong District, Ton Pliw Waterfall, 7 April 2006, T. Insura 62 (BK, BKF); idem, 7 April 2006, T. Insura 63 (BK, BKF); idem, 7 April 2006, T. Insura 64 (BK, BKF).

Figure 5. 

Artabotrys pleurocarpus A habit and mature flower B habit and developing fruit C developing flowers on hooked inflorescence D fruits, showing monocarps borne on very distinct stipes. Photos: T. Insura.

This species was hitherto known from Malacca, Kedah and Perak in Peninsular Malaysia (Sinclair 1955). Specimens of A. pleurocarpus from peninsular Thailand were formerly misidentified as A. kurzii Hook.f. & Thomson or identified to genus level; they were only recently re-identified during our preparation of the Artabotrys treatment for the Flora of Thailand. The specimens from peninsular Thailand and Peninsular Malaysia closely match one another in leaf and fruit morphology and there can be no doubt that they are conspecific. Therefore, this represents the first record of A. pleurocarpus in Thailand. Artabotrys pleurocarpus is distinct among the Thai species on account of its fruit morphology, with relatively few monocarps (up to 9 per fruit) that are prominently beaked (2–3 mm long), quite large (22–30 mm long, 15–20 mm wide) and borne on a long stipe (7–10 mm long). The fruits therefore superficially resemble those of Polyalthia species, but specimens can be easily assigned to Artabotrys if the inflorescence/infructescence hook is present. Although A. kurzii from Myanmar (Pegu) was previously confused with A. pleurocarpus, it bears little resemblance to A. pleurocarpus, differing in its obovate (vs. oblong-lanceolate to oblong-elliptic) leaves, mucronate (vs. caudate to acuminate) leaf apex and short petioles (1–2 mm long vs. 4–6 mm long).

Singapore, Peninsular Malaysia, peninsular Thailand (Fig. 6) and probably Myanmar (see notes), in lowland rain forests.

Figure 6. 

Distributions of A. crassifolius, A. insurae, A. longipetalus and A. pleurocarpus in peninsular Thailand. Only the region in peninsular Thailand is shown; adjacent areas in Peninsular Malaysia and Myanmar are removed.

Peninsular Thailand. Trang Province: Palian District, Lam Plok Waterfall, ca. 20 m elev., 4 May 2010, W. Eiadthong 2010-1 (BK, BKF).

The protologue for A. crassifolius cites a specimen from Martaban in Myanmar. In addition, a regional checklist (Kress et al. 2003) and a forest flora (Kurz 1877) indicate the presence of this species in Tenasserim (Taninthayi), Myanmar. However, Turner (2015) was unable to trace the syntype or any other specimen of this species from Myanmar; our attempts to trace those specimens were likewise in vain. The occurrence of A. crassifolius in Myanmar therefore requires future verification. Artabotrys crassifolius can be distinguished from other species in Thailand as its young twigs, flower pedicels and lower surface of sepals have a dense covering of long appressed hairs that is visible with the naked eye. In Thailand, this species is currently known from a single gathering from Trang, which exhibits the unique indumentum mentioned earlier and has monocarps with shape and size matching A. crassifolius. The specimens of this gathering were previously filed as ‘Artabotrys indet’ and only recently identified for the Flora of Thailand project. Outside of Thailand, A. crassifolius is widespread in Peninsular Malaysia but restricted to the Central Catchment Nature Reserve and Bukit Timah Nature Reserve in Singapore.