Thursday, July 5, 2018

[Botany • 2018] Rohdea harderi (Asparagaceae) • A New Species from northern Vietnam

Rohdea harderi  N. Tanaka, D. P. Hannon & Aver.

in Tanaka, Hannon, Harder, Averyanov & Lahmeyer, 2018.

Rohdea harderi N. Tanaka, D. P. Hannon & Aver., a new species from northern Vietnam, is described and illustrated. It is most closely allied to R. verruculosa from SW China, but differs mainly by the narrower annular appendage at the throat of the perianth tube, explanate, subacute, crenulate, externally smooth perianth segments, smaller stigma and obovoid ovary. Its affinity is briefly discussed on the basis of floral traits. A key to the species known from Vietnam is also provided.

Key Words: Convallarieae, Indochina, phenotypic traits, Tupistra

Fig. 1. Rohdea harderi. A habit with flowering scape; B aerial basal portion of plant; C habit with scape after flowering; D & E flowers; F fruit; G seed; H inflorescence; J inflorescence in late anthesis; K inflorescence after flowering.

Photographs A – C, F – K by D. P. Hannon, D & E by S. C. Lahmeyer. Layout by N. Tanaka.

Fig. 2 Flower and bracts of Rohdea harderi.
A flower, front view; B flower vertical section with intact pistil inside perianth tube, annulus arrowed; C partial perianth with stamen removed from near base, ventral view with annulus arrowed; D – G pistil, D side view; E trisect stigma on top, view from above; F ovary torn to show locular interior bearing 4 ovules on placentae; G ovary, cross-section, showing interior with ovules; H – K stamens: H dorsal view; J side view; K ventral view; L sterile bract from distal portion of peduncle, ventral view, expanded; M floral bract (right) and bracteole (left; arrowed) on part of rachis.

 Scale bar at A for A, B, L, M; at D for D – K. 
Drawn from a cultivated plant at Huntington Botanical Gardens (accession number 90679). Drawn by N. Tanaka.

Rohdea harderi N. Tanaka, D. P. Hannon & Aver. sp. nov. 

Type: Vietnam, Son La province, D. K. Harder et al. 7276, dried herbarium specimen prepared by D. P. Hannon s.n. on 21 April 2017 from a plant cultivated at Huntington Botanical Garden (HBG 90679) (holotype, HNT 13048!).

Recognition: Most closely allied to Rohdea verruculosa (Q. H. Chen) N. Tanaka (Tanaka 2003: 332, excluding Tupistra annulata H. Li & J. L. Huang and its homotypic synonym), but differs from it chiefly by the narrower annulus (0.5 vs 1 – 1.5 mm wide) at the throat of the perianth tube, explanate, crenulate, subacute, smooth perianth segments (vs incurved, nearly entire, caudate(-filose), externally verruculose segments), smaller stigma (0.7 – 0.8 vs c. 1.3 mm across), and obovoid ovary (vs ovoid or globose ovary). 

Distribution: Endemic to NW Vietnam: Dien Bien and Son La provinces.

In Dien Bien province, Rohdea harderi occurs on shady forest floor or among rocks in humid, highly degraded primary evergreen broadleaved forest on very steep slopes of mountains composed of solid limestone at elevations 1100 – 1300 m a.s.l. (Averyanov et al. as CPC 2115, LE).

In Son La province, it occurs as undergrowth on light to heavily shaded forest floor in secondary or primary forest with some timber species (mainly Burretiodendron Rehder and conifers) removed along ridgetop of crystalline limestone around 1468 m in elevation (Harder et al. 7276 as D. P. Hannon s.n., HNT 13048).

Etymology: The specific epithet honours Dr Daniel K. Harder as founder of the Missouri Botanical Garden’s Viet Nam Botanical Conservation Program, who discovered, collected and brought the new species into cultivation, thereby greatly contributing to the improvement of our knowledge on the plant.

Noriyuki Tanaka, Dylan P. Hannon, Daniel K. Harder, Leonid V. Averyanov and Sean C. Lahmeyer. 2018. Rohdea harderi (Asparagaceae), A New Species from northern Vietnam. Kew Bulletin. 73:31.  DOI: 10.1007/s12225-018-9756-3

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