Artabotrys longipetalus J.Chen & Eiadthong, 2020

Chen, Junhao & Eiadthong, Wichan, 2020, New species and new records of Artabotrys (Annonaceae) from peninsular Thailand, PhytoKeys 151, pp. 67-81 : 67

Artabotrys longipetalus J.Chen & Eiadthong sp. nov. Fig. 2A, B

Diagnosis.

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).

Type.

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]).

Description.

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.

Phenology.

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

Distribution and habitat.

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.

Preliminary conservation status.

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].

Additional specimens examined.

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).

Notes.

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.

Figures

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.

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.