Didymocarpus puhoatensis X.Hong & F.Wen, 2018

Hong, Xin, Li, Zhen-Long, Maciejewski, Stephen, Wen, Fang & Do, Truong Van, 2018, Didymocarpus puhoatensis (Gesneriaceae), a new species from Vietnam, PhytoKeys 94, pp. 87-93 : 88-91

Didymocarpus puhoatensis X.Hong & F.Wen sp. nov. Figures 1 , 2

Diagnosis.

Although it is morphologically similar to D. brevicalyx , it differs by stem densely pubescent, orbicular purple bracts, apices of calyx lobes obtuse, filaments glabrous, staminodes 2; and also similar to D. epithemoides , but differs from the latter in having purple calyx, funnel-form corolla, 4-5 cm long, glabrous, dark purple-blackish, ovary glandular puberulent.

Type.

VIETNAM. Ngh ệ An Province : Qu ế Phong , Thong Th ụ, Pu Hoat Nature Reserve (Khu B ảo tồn thiên nhiên Pù Ho ạt), 19°52'30.5"N, 104°56'15.1"E, alt. 390 m, 18 July 2014, flowering, Truong Van Do et al. VNM-CN439 (holotype: IBK; isotype: VNM) .

Description.

Deciduous, perennial, lithophytic herb, 10-30 cm tall. Stems erect, single, sparsely puberulent to glabrescent, the upper, leaf-bearing part and young stems densely covered with whitish multicellular eglandular hairs. Dry season plants unknown. Rainy season leaves opposite, anisophyllous; petioles terete, 0.5-2.5 cm long, densely covered with multicellular eglandular hairs as on the stems; blades asymmetrically ovate, 6-10 cm long, 5-8 cm wide, apex bluntly acute, base slightly oblique, obtuse- cuneate, margin finely serrate or finely doubly serrate, papery, upper surface densely covered with whitish multicellular eglandular hairs, green, lower surface sparsely covered with hairs as on upper surface, pale green, venation pinnate, secondary veins 4-8 on each side of midrib, mostly opposite sometime alternate, obscure above, prominent beneath, covered with whitish multicellular eglandular hairs. Inflorescences terminal or from the upper leaf axils, cymose, ca. 12 cm long, 4-10 (-30) flowered; peduncles slender, 6-10 cm long, light green, sparsely covered with multicellular glandular hairs; pedicels 1-1.5 cm long, pale green, with indumentum as on the peduncle. Bracts paired, orbicular, ca. 5 mm long and wide, green to pale purple, glabrous. Calyx consisting of a tube and shallowly 5-lobed margin, symmetrical, campanulate, 6 mm long, glabrous, somewhat tawny to pinkish purple, tube ca. 5 mm long, 3 mm in diameter; lobes triangular, ca. 1 mm long, ca. 2 mm wide, apices obtuse. Corolla funnelform, 4-5 cm long, glabrous outside, blackish purple, becoming light purple at base; tube ca. 3.5 cm long, base narrow, ca. 2 mm wide, dilated and slightly ventricose towards the throat; widest at throat, diameter ca. 9 mm; corolla bi-lipped, lobes suborbicular; lower lip 3-lobed, ca. 8 mm long, 6 mm wide, more or less equal; upper lip 2-lobed, ca. 4 mm long and wide. Fertile stamens adnate to corolla ca. 1.5 cm from base; anther locules, ca. 2.5 mm long, ca. 1.5 mm wide, densely covered with brownish multicellular eglandular hairs; filaments slender, ca. 1 cm long, white, glabrous; staminodes 3, reduced to thin filaments, lateral ones 3 mm long, the other one 1 mm long, glabrous, adnate to corolla ca. 1 cm from base. Disc cylindrical, ca. 2 mm long, margin irregular. Pistil ca. 2-3 cm long; ovary narrowly linear, ca. 2 cm long, sparsely glandular puberulent, base reddish, with purple tinge towards stigma and apex green; stigma 1, peltate, concave, papillose, cream. Capsules unknown.

Phenology.

It flowers and fruits from June to September.

Etymology.

The specific epithet is derived from the type locality, Pu Hoat Nature Reserve, Nghệ An Province, Vietnam.

Distribution and habitat.

This new taxon is an endemic species from Pu Hoat Nature Reserve of Vietnam. The species grows on limestone rocks in tropical monsoon forest with sufficient seasonal run-off water, at an elevation of 390 m a.s.l. It distributes much lower in altitude and the habitat is much hotter and more humid than other species with stems of the genus.

Preliminary conservation assessment.

As population information of Didymocarpus puhoatensis is still unclear, it is not appropriate to make an assessment of the extinction risk faced by this new taxon. Thus, the category of Data Deficient (DD) should be appropriate, according to IUCN (2016) criteria. Fortunately, the known habitat of the species is protected as part of a nature reserve. Besides prolonged droughts and illegal logging in the area, there are other potential risks to the persistence of this new species.

Key to the species of Didymocarpus in the Vietnam

1	Ovary smooth	2
-	Ovary hair	4
2	Corolla outer hair; leaf blade ovate or elliptic, ca. 4-10 × 2-6 cm	D. pulcher
-	Corolla outer smooth; leaf blade near round or broadly elliptic, ca. 1-4 × 1-4 cm	D. kerrii
4	Base of leaf often axisymmetric; bract lanceolata, ca. 2-3 mm long; sepal tube ca. 3 mm long, sepal lobed ca. 1-1.5 mm long	D. poilanei
-	Base of leaf often oblique; bract elliptic ovate or orbicular, ca. 3-8 mm long; sepal tube ca. 8-9 mm long, sepal lobed ca. 2-3 mm long	5
5	Peduncle 4-10 cm, glabrous; bracts connate at base; calyx 1-1.2 cm; corolla 3-4 cm, purple to pinkish purple	D. purpureobracteatus
-	peduncles 6-10 cm, glandular hairs; bracts separate; calyx 6 mm; corolla 4-5 cm, blackish purple	D. puhoatensis

Figures

Figure 1. Didymocarpus puhoatensis X. Hong & F. Wen A Habitat B Adaxial surface view of leaf blade C Adaxial surface view of leaf blade D Cyme with flowers, showing the bracts E Lateral view of corolla, showing the calyx consisting of a tube.

Figure 2. Flower of Didymocarpus puhoatensis X. Hong & F. Wen A-B Frontal view of corolla, showing the disc-like stigma C Top view of corolla D Upward view of corolla E Opened corolla, showing stamens and staminodes F Pistils without corolla.