Durio gerikensis M.N.Faizal, Edward, Latiff & Hadrul, 2022

Ghazalli, Mohd Norfaizal, Hashim, Mohamad Hadrul, Besi, Edward Entalai, Mat-Esa, Muhammad Ikhwanuddin, Zaini, Ahmad Zaki, Saranum, Mohd Masri, Salleh, Salmaniza, Jajuli, Rosliza, Sah, Muhammad Shafie Md, Talip, Noraini & Latiff, A., 2022, Durio gerikensis (Malvaceae), a new Arilless Durio from Hulu Perak, Malaysia, Phytotaxa 543 (1), pp. 21-30 : 22-27

Durio gerikensis M.N.Faizal, Edward, Latiff & Hadrul , sp. nov. ( Figs 1 , 2 , 3 , 5 & 6 )

Diagnosis:— Durio gerikensis morphology is partially similar to D. lanceolatus . It has oblong-lanceolate leaves (vs. elliptic-lanceolate to ovate), base acute (vs. acute to round); flowers in 6–28 flowered cymes, on young to older branches, reddish pink petals (vs. 3–4 flowered cymes, on older branches, yellow petals); and its fruit is arilless, not edible and contains two to four valves (vs. creamy aril, almost tasteless and unpalatable). When compared to D. singaporensis fruits (another species with arilless fruits) it has 5-lobed, white leathery aril which later dried and not edible. Additionally, D. gerikensis fruits can be readily differentiated from both D. lanceolatus and D. singaporensis with the persistent calyx on the mature fruits and the four-valved fruits (vs. early caducous calyx and more than 4- valved fruits).

Type:— PENINSULAR MALAYSIA, Perak, Gerik, 29 th July 2020, N 5° 24.77906; E 101° 1795603, Mohd. Norfaizal, Hadrul, Muhamad Ikhwan , Edward Entalai , Mohd Masri MDI 12456 [holotype MDI; isotype KEP] .

Description:— A tree of medium to big size, ca. 40 m tall, 1.7–2.3 m in diameter, vigour high; main trunk 2.5–3.24 m in height; canopy shape oval-irregular, branching density medium to dense, branching pattern semi-erect; bark rough, faintly lenticellate, greyish to light brown. Leaf petiole 1.3–1.5 cm long, terete. Leaves oblong-lanceolate, 9.3–11.6 × 2.7–4.1 cm, thin leathery, apex acute, acumen 4–(7)– 9 mm long, base rounded, margin undulate, upper surface dark green, glabrous with sparse simple, unicellular trichomes, with sparse, slightly dull, lower surface slight golden-green, densely covered with layers of dentate-lepidote scales, simple peltate scale and 5–20-armed stellate trichomes with a central cushion, midribs channelled above, pointed below in triangle shape, lateral veins 17–19 pairs, conspicuous on upper surface, inconspicuous on lower surface. Inflorescences composed of 6–28-flowered fasciculate cymes, observed on young and old branches and twigs. Flower bud ovoid to globose, apex rounded, 1.4–1.65 × 1.3–1.45 cm, peduncle 1.4–1.7 cm long. Pedicel terete, 2.4–3.4 cm long. Epicalyx 2–3-lobed, lobes ovate to subovate, 1.5–1.8 × 2 cm, apex rounded, green to brownish golden, densely stellate with simple, unicellular hairy inside, brown, rough scaly outside. Calyx 5- lobed, lobes 0.3–0.55 × 0.7–0.8 cm, golden brown, glabrous to sparsely hairy inside, green to yellow, rough, scaly outside. Petals 4–5, pink to light pink, spathulate, 2.1–2.7 × 0.7–1.2 cm, with minute hairs outside. Stamens arranged in 5–7 phalanges, each phalanx branched at 6–7 mm with 4–7, pink or cream to goldenbrown, 2–3.5 cm long, unequal, sparsely glabrous to stellate hairy filaments; anthers reniform, in a cluster of 5–8, dehiscing by slits, yellowish to golden-brown. Ovary ellipsoid to sub-ovoid, densely covered with appressed, golden scales, 7–8.5 × 4–6 mm; style ca. 22 mm long, erect, covered with stellate hairs at distal and proximal ends; stigma globose to capitate, yellow to brownish-golden. Fruit dry, globose, 6.1–7.5 × 5.2–6.1 cm, dehiscent (dehisce before drooping) capsules with persistent calyx, epicarp spinulate, green to golden-yellowish, apex blunt or slightly pointed on the beak, stalk 1.3–1.7 cm long, two- to four-valved (usually three), each valve with only single arilless seed. Seed ovoid, 3.8–4.5 × 3.1–3.8 cm, brown.

Distribution and habitat:— Durio gerikensis has been found in two adjacent locations (Lenggong and Gerik) in the district of Hulu Perak, Perak, Peninsular Malaysia. The species grows in a mixed dipterocarp forest, near Orang Asli (Malayan aborigines) settlements; and associated with Artocarpus elasticus Reinw. ex Blume (Reinwardt 1825: 481) , A. rigidus Blume (Blume 1825: 482) , Pentaspadon motleyi Hook. f. (Hooker 1860: 168), Durio zibethinus (Murray 1774: 581) , Uvaria grandiflora Roxb. ex Hornem. (Roxburgh 1832: 665) , Lithocarpus elegans (Blume 1825:208) Hatus. ex Soepadmo ( Soepadmo 1970: 236) . Presently known only from these two individuals in situ observation in Hulu Perak and extant population of this species is still under evaluation. We propose that this species status as Critically Endangered (CR) species, which is evaluated as facing an extremely high risk of extinction in the wild with only a few individuals observed in the forest. For ex situ conservation, we successfully germinated twenty (20) seeds and it is intended for field gene bank conservation program in Malaysian Agricultural Research and Development Institute (MARDI), as well as for distribution to other existing botanical gardens or parks in Malaysia. We also advise the Forestry Department of Peninsular Malaysia in which those localities observed to protect the living specimens for future references.

Phenology:— Flowering in April to May, fruiting in July to early August.

Etymology:— Named after the type locality, Gerik, Hulu Perak, Peninsular Malaysia.

Notes: — Durio gerikensis also shares the similarities with D. lanceolatus in oblong-lanceolate or elliptic-lanceolate leaves with acute to rounded base, and D. singaporensis in having arilless seeds and more than 4-valved fruit. But D. gerikensis differs from latter two by having different morphological characters ( Table 1 ).

Additional specimen examined:— Durio gerikensis: PENINSULAR MALAYSIA, Perak, Lata Lawin FR, Lenggong, 29 th July 2020, Mohd Norfaizal, Hadrul, Muhamad Ikhwan, Edward Entalai, Mohd Masri MDI12459 (MDI). Durio lanceolatus: BORNEO-SABAH : Beaufort Hill, SAN 36983 (SAN); Ranau, SAN 128833 (SAN); 1 mile Northeast of Beaufort, SAN 15060 (KEP); Tawau, Elphinstone, SAN 21779 (SING).— SARAWAK: Bukit Raya, Kapit, S22284 (SAR); Gunung Buri, 25 th Mile, 1 st /2 nd Div. boundary, S36993 (SAR); Ng. Mengiong, Ulu Balleh Kapit, 3 rd Division Mixed dipterocarp forest on ridge at 1000ft altitude, S29180 (SING); Lundu, Gunung Ending, path to summit from waterfall, lowland dipterocarp forest, SAN 15373 (SING); Syarikat Salmas, Sampadi, F.R. Lundu, 1 st Division, S37805 (KEP; SAR); Gunung Buri, 75 th mile, 1 st Division, S36933 (SAR); Ulu Ropan, Belalong watershed, S5265 (KEP); Ulu Ropan, S5253 (SAR); Gunung Buri 7 th mile, 1 st /2 nd division boundary, S36933 (KEP); Ng. Mengiong, Ulu Balleh, Kapit, 3 rd division, S29180 (KEP).— BRUNEI: Ulu Ropan-Belulong watershed, BRUN 5652 (KEP), Pseuadgan FR, BRUN 80159 (KEP). Durio singaporensis Ridl. : PENINSULAR MALAYSIA-TERENGGANU: Sg. Terengganu near Kuala Kerbat, Kuala Lasir, FRI 20236 (KEP); Kemaman, low ridge North-west from Pengkalan Kajang, FRI 20187 (KEP); Terengganu hills, Sg. Terengganu, near Kuala Kerbat South of Kuala Lasir, FRI 20236 (KEP); Jerangau, Dungun, KEP 80808 (SING); Ulu Sg. Terengganu, Ulu Terengganu, KEP 8462 (KEP); Ulu Sg. Terengganu, Kuala Penang, Ulu Terengganu, FRI 8462 (SAR); Sg. Terengganu, Kemaman, Pengkalan Kajang, FRI 20817 (SAR).—PAHANG: Lesong FR, FRI 28362 (KEP); Pancing Forest, 15 km north to Pancing, Kuantan, KEP 10466 (KEP); Eastern edge of Chini FR, South of Tasik China, FRI 17287 (KEP); Eastern edge of Chini FR, South of Tasek Chini, FRI 17287 (SING); Lesong FR, FRI 19839 (KEP); G. Tapis, FRI 10928 (SAR); Lesong FR, Pahang, FRI 8656 (SAR); Eastern edge of Chini FR, South of Tasik Chini, FRI 17287 (SAR); Ridge to G. Tapis, FRI 10928 (SAR); Bt. Kajang FR, FRI 45499 (KEP).—NEGERI SEMBILAN: Gunung Angsi FR KEP23695 (KEP).—JOHOR: Sg. Kayu, Mawai, Jemaluang Road KEP 29257 (KEP); Sg. Sedeli, KEP 36974 (KEP), Gunung Janing, Labis FR, Ulu Endau, KEP 110407 (KEP), Gunung Berlumut, FRI 8780 (SING); N.E. Johor, lenggor FR Hillside, at. 500’, FRI8656 (SING), Sungai Sedili below Mawai, KEP 36974 (SING); S. Kayu, Mawai, Jemaluang road, Field No. 29257 (SING); Kluang FR Hillside, FRI 7534 (KEP), Gunung Berlumut, FRI8780 (KEP); Renggam FR, Johor, FRI 2185 (KEP); Road to Sg. Kahang, North to Labis FR FRI 17789 (SAR); Kuala Kemapan HS Labis, W.D.F., FRI 34152 (KEP).

Figures

FIGURE 1. Durio gerikensis A) tree (habit) at the type locality. B) branching pattern. C) leaves. D) bark. E) abaxial surface of the leaves. F) adaxial surface of the leaves. Photographs (A) by Mohd Masri Saranum; (B–F) by Mohd Norfaizal Ghazalli.

FIGURE 2. Durio gerikensis A) fruiting leafy twig. B) different fruit stages, and arilless seeds. C) arilless seeds (close up). D) dehisced fruits with three lobes (left) and one lobe (right). (E) immature fruit (F) mature and dehisced fruit with persistent calyx. Photographs A–F by Mohd Norfaizal Ghazalli.

FIGURE 3. Durio gerikensis A) inflorescence young flower buds. B) inflorescences flower buds on branches. C) inflorescences on branch. D) flowers in fasciculate cymes. E) epicalyx. F) opened epicalyx. G) calyx. H) calyx adaxial view. I) stamens in 5 phalanges. J) petals. K–L) pistil (ovary, style and stigma) and pedicel. N) full part of the pistil and pedicel. O) portion of style and stigma at the end of style. P) ovary. Q) phalanges of stamens. R) close up of stamens. S) dehisced anthers. Photographs A–C by Mohd Norfaizal Ghazalli; D–S by Edward Entalai Besi.

FIGURE 5. Durio gerikensis A) opened epicalyx. B) intact epicalyx. C) calyx adaxial view. D) calyx. E) stamen. F) ovary. G) petal. H) anther. I) pistil and pedicel. J) phalanges of stamen. K) inflorescence. L) flower bud. Illustrated by Zulkifli Zainol Alam.

FIGURE 6. Durio gerikensis A) fruit. B) fruit attached to the branch. C) abaxial view of the fruit. D) dehiscent fruit. E) leaf morphology with dentate-lepidote trichome, 18–20-armed stellate trichomes, dentate-lepidote scales and 5-armed stellate trichomes with a central cushion. Illustrated by Zulkifli Zainol Alam.