Benstonea fortuita Callm. & Buerki 2016, spec. nova

Benstonea fortuita Callm. & Buerki, spec. nova (Fig. 2).

Typus: MALAYSIA [BORNEO]. State Sabah: Tenom Dist., 21 km from Tenom on road to Sipittang, Lumako FR, 5°00’22”N 115°51’53”E, 620 m, 9.X.2014, fr., Callmander et al. 1197 (holo-: G [G00341180]!; iso-: BM!, SING!, SAN!)

Benstonea fortuita Callm. & Buerki is distinguished among the genus by its subacaulescent habit, its leaf abruptly attenuate at the apex with a short apicule (0.5-1 cm), its ventral pleats armed, its stout acuminate style (3-4 mm), slightly curved proximally, and its solitary globose syncarp.

Subacaulescent shrub <1m tall. Leaves glaucous, white below, 100-120 cm long, 4-5 cm wide in the middle, 3.5 cm wide near the sheath, abruptly attenuate in the upper part, shortly apiculate (c. 0.5-1 cm long), narrowing towards the base, subcoriaceous; marginal prickles beginning at 6-9 cm above the base and extending to the apex, antrorse, c. 2 mm in the lower third, 2-6 mm apart, to c. 1 mm in the mid third, 5-10 mm apart; minute in the distal third, c. 2 mm apart; ventral pleats armed in the last 25-28 cm of the leaf with minute prickles; sheath not auriculate, whitish. Infructescence terminal, monosyncarpic, erect at maturity; syncarp in the middle of the clump of leaves, pale green, subglobose, c. 6 cm in diam.; peduncle straight, 10 cm long, 0.7 cm wide at apex, trigonous, white in vivo, longitudinal veins visible, covered with 4-5 bracts scars. Drupes c. 150, 23- 25 mm high, 4-6 mm wide, c. 6 mm in depth, 5-6-angled; pileus pyramidal, pale to dark green in vivo, shrunk when dried, 8-10 mm high (excluding style). Style unique, stout acuminate, 3-4 mm long, slightly curved proximally; stigmatic groove brown in vivo, linear, positioned on abaxial side; endocarp c. 6 mm long, walls c. 0.4 mm thick; seed locule elliptic, 4 × 3 mm; apical mesocarp fibrous, discrete, c. 4 mm long; lower mesocarp fibrous. Staminate plant unknown.

Etymology. – This species is only known from a single population where only one fruiting individual was observed. We were very fortunate to come across this rare and discrete taxon and the species epithet reflects our feeling when we discovered this new Benstonea.

Distribution and ecology. – Benstonea fortuita is only known by few individuals in southwestern Sabah in the lowland Dipterocarp forest at an altitude of 600 m (Fig. 1).

Conservation status. – Despite being known from a Forest Reserve [FR], this species is considered rare and seriously threatened. The only known population is located in the southern tip of the Lumako FR in a secondary Dipterocarp forest where few dominant trees still protect the understorey due to past logging. Benstonea fortuita is assigned a preliminary status of “Critically Endangered” [CR B1ab(i,iii,iv,v)] following IUCN Red List Categories and Criteria (IUCN, 2012).

Notes. – The overall morphology of the new species can be compared to: B. glaucophylla (Ridl.) Callm. & Buerki, B. parva (Ridl.) Callm. & Buerki, and B. undulifolia (Ridl.) Callm. & Buerki. All three species share wide, abruptly attenuate leaves and a solitary syncarp with B. fortuita. Nevertheless, the new species can easily be discriminated from these species by the combination of characters presented in Table 1.

In their phylogeny, BUERKI et al. (2016) showed that the new species B. fortuita belongs to clade I together with the endemic Bornean B. platystigma (Martelli) Callm. & Buerki. Although both species have the same ecology (lowland humid forest), B. fortuita can easily be distinguished from B. platystigma by its habit (subacaulescent shrub <1 m tall vs. low shrub), leaves (wide, 4.5 cm and apex abruptly attenuate vs. narrow, 1.5 cm and apex gradually attenuate), style and stigmatic groove (stout acuminate, slightly curved proximally with a linear stigmatic groove vs. antrorsely bent down, flattened proximally with a subreniform groove) and fruits (pale green syncarp when ripe vs. bright red syncarp when ripe).