Macrosolen (Blume) Rchb. is a small parasitic shrub in the family Loranthaceae. The genus is characterized by being totally glabrous with 6-merous flowers subtended by one bract and two bracteoles (often connate), reflexed corolla lobes at anthesis, and 4-locular anthers. The genus comprises ca. 40 species widely distributed in tropical South and Southeast Asia. In Vietnam, it has been recorded by de Loureiro (1790, as Loranthus), Lecomte (1915, as Elytranthe), Danser (1938) and Hô (2003), and recently a taxonomic revision of Loranthaceae in the country by Han (2014) enumerated seven species of Macrosolen: M. annamicus Danser, M. avenis Danser, M. bibracteolatus (Hance) Danser, M. cochinchinensis (Lour.) Tiegh., M. dianthus Danser, M. robinsonii (Gamble) Danser and M. tricolor (Lecomte) Danser.
During botanical surveys in Bidoup Nui Ba National Park, Lam Dong Province, southern Vietnam in 2016, we encountered an undescribed species of Macrosolen. We here describe this new species as Macrosolen bidoupensis Tagane & V.S.Dang, and provide illustrations, and a key to the species of Macrosolen in Vietnam.
In addition to the morphological examination, DNA sequences are extremely helpful for delimiting species (Hebert and Gregory 2005, Dick and Webb 2012). We sequenced two DNA barcode regions of rbcL and matK following the recommendation of CBOL Plant Working Group (2009).
Materials and methods
To verify the validity of the new species, we undertook morphological comparisons to closely related species based on herbarium specimens (ANDA, BKF, BO, BRUN, FU, HN, KYO, SAR, TNS, VNM), specimen images on the web (e.g. JSTOR Global Plants, http://plants.jstor.org/ and Muséum National d’Histoire Naturelle, http://www.mnhn.fr/), and consulting the relevant literature (e.g. Barlow 1995, 1997, 2002, Qiu and Gilbert 2003, Hô 2003, Han 2014).
DNA amplification and sequencing of portions of the chloroplast genes rbcL and matK followed established protocols (Kress et al. 2009, Dunning and Savolainen 2010) as in Toyama et al. (2015).
Macrosolen bidoupensis Tagane & V.S.Dang, sp. nov. (Figures 1, 2)
Macrosolen bidoupensis is similar to Macrosolen tricolor Danser of China, Laos and Vietnam in leaf shape and size and by possession of a 2-flowered umbel, but differs in having a sessile to very short petiole (up to 0.7 mm long in M. bidoupensis vs. 2–3 mm long in M. tricolor), more lateral veins (4 or 5 vs. 2 or 3 pairs), slightly cordate to rounded leaf bases (vs. cuneate) and a basally green corolla tube (vs. reddish around the basal 1/3). The leaf shape is also somewhat similar to Macrosolen platyphyllus Danser of Thailand, Peninsular Malaysia and Borneo, but easily distinguished in having much smaller leaves and flowers, and very short petioles.
Figure 1. Macrosolen bidoupensis Tagane & V.S.Dang. A Branch with flower buds B 2-flowered inflorescence C Flower with corolla tube opened D Fresh fruit E Dried fruit F Seed G seed (left) and longitudinal section of seed (right). Materials: Tagane et al. V4083 (KYO). Drawn by N. Komada.
Figure 2. Macrosolen bidoupensis Tagane & V.S.Dang. A Branch with flower buds B Flower C Fruits. Photos by Tagane et al. V4083.
VIETNAM. Lam Dong Province, Bidoup Nui Ba National Park, in lower montane evergreen forest, 12°10'34.7"N, 108°41'08.4"E, alt. 1533 m, 21 Feb. 2016, with flowers, Tagane S., Nagamasu H., Naiki A., Dang V. Son, Ngyuen V. Ngoc, Binh T. Hoang & Wai J. V4083 (holotype-KYO!, fl. spirit collection; isotypes NTU!, the herbarium of Bidoup Nui Ba National Park!, VNM!).
Hemi-parasitic shrub, 25–40 cm tall, totally glabrous. Branches terete, grayish to grayish brown, lenticellate. Leaves opposite; blade elliptic, broadly elliptic, broadly ovate-elliptic, or circular, 1.2–4.8 × 1.2–3.5 cm, coriaceous, apex broadly obtuse to rounded, base slightly cordate to rounded, margin entire, grayish green and slightly lustrous adaxially, dull olive abaxially, midrib prominent at basal 1/3 to 1/2 abaxially, secondary veins 4 or 5 pairs, obscure or visible adaxially, obscure to faintly visible abaxially; petiole to 0.7 mm long. Inflorescences axillary, sometimes at older leafless nodes, 2-flowered umbels; peduncle ca. 0.9 mm long. Pedicel 1.1–1.5 mm long; central bract suborbicular, ca. 1 mm long, bracteoles suborbicular, connate, ca. 1 mm long; mature buds 2.8–3.2 cm long; calyx limb (calyculus) annular, ca. 0.7 mm long; corolla green tinged with red at top of tube and lobes, symmetrically 6-winged at about two thirds the length, tube 2.2–2.4 cm long in anthesis, gradually dilated, inflated, slightly curved, lobes lanceolate, 6–8 mm long, reflexed in anthesis; stamens 6, anthers ca. 2.3 mm long, filaments basally adnate to corolla tube, free part 2.3–3.3 mm long; ovary 2.8–3.3 mm long; style 2.8–3.2 cm long, stigma capitate. Berry reddish orange, subglobose to slightly depressed-barrel-shaped, ca. 8 mm high, ca. 6 mm wide, ovoid when dry, apex beaked by calyx limb. Seed 1, ellipsoidal, ca. 5 mm high, ca. 3 mm wide, longitudinally 6-grooved. The measurements of the flower characters are derived from the spirit collection.
Other specimen examined in Vietnam
Bidoup Nui Ba National Park; in lower montane evergreen forest, 12°10'34.9"N, 108°41'04.4"E, alt. 1533 m, 22 Feb. 2016, with fruits, Tagane et al.V4169 (FU, NTU, the herbarium of Bidoup Nui Ba National Park, VNM).
Flowering and fruiting specimens were collected in February.
Distribution and habitat
Vietnam (so far known only from Bidoup Nui Ba National Park, Lam Dong Province). In lower montane evergreen forest, ca. 1500 m altitude.
GenBank accession no
Tagane et al. V4083: LC259010 (rbcL), LC259011 (matK). The partial rbcL sequence of M. bidoupensis was identical to M. tricolor (GenBank accession no. HQ317771) of the total 517 bp and differed at 3 bases of the 518 total from M. cochinchinensis (KP094775 and HQ317768). The partial matK sequence of M. bidoupensis differed at 23 bases from M. cochinchinensis (EU544439) of the 813 total.
The specific epithet bidoupensis is derived from its type locality.
Least Concern (LC). Bidoup Nui Ba National Park is located on Central highland of Vietnam. It covers ca. 700.38 km2 and is the core zone of the Langbiang biosphere reserve (Bidoup-Nui Ba National Park 2016). Macrosolen bidoupensis is commonly found in the lower montane evergreen forest in the national park. Since the forest is widely seen and well-protected, we suggest this status as LC according to IUCN (2012).
A similar species, Macrosolen tricolor is known from lower elevations (below 100 m, Qiu and Gilbert 2003), and the two species do not occur sympatrically.