Amentotaxus hekouensis L.M. Gao, 2019

Gao, Lian-Ming, Tan, Shao-Lin, Zhang, Gui-Liang & Thomas, Philip, 2019, A new species of Amentotaxus (Taxaceae) from China, Vietnam, and Laos, PhytoKeys 130, pp. 25-32 : 26-28

Amentotaxus hekouensis L.M. Gao sp. nov. Figs 2 , 3 , Table 1

Diagnosis.

Amentotaxus hekouensis L.M. Gao resembles A. argotaenia (Hance) Pilg., but differs in its larger leaf size (8-12.5 cm × 0.9-1.4 cm), long acuminate leaf apex, leaf margin flat with slightly wavy, stomatal bands white or greenish-white with 25-30 rows, stomatal bands equal or slight narrower than marginal bands; pollen-cone racemes borne 1-2, cones in 12-16 pairs, microsporophylls 6-8, each with 4-6 pollen sacs.

Type.

CHINA. Yunnan: Honghe, Hekou County, Nanxi Town, Longyinchong village, 22°41'8.9"N, 104°01'11.5"E, 926 m alt., 16 April 2016 (with male cone), G. L. Zhang, GLM-164271 (holotype: KUN!; isotypes: KUN!)

Morphological description.

Small tree to 4-5 m tall; branch cylindric or subtetragonal, grey; leafy branchlets ascending or sub-erect, broadly rectangular to oblong-elliptic in outline, 6-12 × 11-20 cm, axis green in 1st year, greenish-yellow in 2nd and 3rd years, quadrangular or subterete in cross section. Leaves borne at 50-80° to branchlet axis, distichous, twisted at the short petiolate or nearly sessile base, petiole 2-4 mm long, almost opposite, 4-6 leaf pairs on each branchlet; leaves leathery, thin, linear or linear-lanceolate, 8-12.5 × 0.9-1.4 cm, straight, slightly falcate at the apex, cuneate at base, asymmetric, apex long acuminate, leaf margin flat or slightly down-curved, usually slightly wavy; leaf marginal band dark green in fresh, yellowish-green in dry, 2.5-3.2 mm wide; stomatal bands white or greenish-white, 2.1-3.0 mm wide, equal or slight narrower (> 3/4) to marginal bands, 25-30 rows, densely arranged; midvein slight sunken or flat adaxially, raised abaxially, 1.2-2.0 mm wide, narrower than the stomatal bands and marginal bands, green, same colour as the branchlet. Male-cone racemes borne 1-2, ca. 8.0 cm long; cones in 12-16 pairs, ovoid, cones at base maturing earlier than those at apex; microsporophylls 6-8, peltate, each with 4-8 pollen sacs. Ovulate cone and mature seed unknown. Male cones maturing March to April.

Additional specimens examined.

CHINA. Yunnan: Hekou County, Nanxi Town, 20 Sept 2006, L. M. Gao et al. GLM-06209 (KUN!); ibid., 20 Oct 2012, L.M. Gao GLM-123943 (KUN!), ibid., 31 Jan 2016, L. M. Gao et al. GLM-164258, GLM-164259 (KUN!), ibid., 21 Oct. 2001, Y. M. Shui et al. 15078 (KUN); Funing County, Long-may, 24 April 1940, C.W. Wang 88812 (KUN); Malipo County, 4 Jan. 1940, C.W. Wang 86175 (KUN). Vietnam. Lao Cai: Muong Khuong, Nam Chay commune, Moi village, 21 Nov. 2009, CKF team CKF250 (KUN, CPC, CMBG); Hoa Binh: Mai Chau, Pa Co commune, 3 Dec. 2003, S.G. Wu et al. WP413 (KUN). Laos. Xiang Khouang: Phak Leung Mt., Tanh village, Dec. 2008, X. Gong GX-5 (KUN).

Distribution and ecology.

Amentotaxus hekouensis L.M. Gao has only been found in small disjunct areas in China (Funing, Malipo and Hekou County, Yunnan Province), Vietnam (Muong Khuong, Lao Cai Province; Mai Chau, Hoa Binh Province) and Laos (Xiang Khouang) ( Figure 4 ). It is confined to the montane evergreen forest on lime stone mountains at elevations between 850 and 1200 (-1750) m. In part of its distribution along the border between China and Vietnam, it is sympatric with A. yunnanensis .

Phenology.

Male cones of Amentotaxus hekouensis mature in March to April; seeds have not been seen so far.

Etymology.

The specific epithet refers to the type location in Hekou County.

Conservation status.

Several surveys have been carried out in this region since 2006 and only a few small trees of the new species are known. Amentotaxus hekouensis occurs in small and isolated patches of forests at very low densities. All the known localities are subject to degradation from surrounding agriculture and forest clearance. Given its montane habitat, the new species may also be susceptible to the impacts of climate change. The combination of a restricted, fragmented distribution with very limited Area of Occupancy, small population size and habitat conversion and destruction throughout its range indicate that its IUCN status should be Endangered under Criterion B2ab(ii,iii) ( IUCN 2016b).

Figures

Figure 2. Amentotaxus hekouensis L. M. Gao (from the holotype, drawn by Ling Wang). A Branchlets with male cone B pollen sacs.

Figure 3. Amentotaxus hekouensis L. M. Gao. A Habitat B habit C branchlet with adaxial leaves D branchlet with abaxial leaves E young shoot F branchlet and male cone racemes with microsporophylls G male cone racemes H microsporophylls and pollen sacs.

Figure 4. Geographical distribution of Amentotaxus hekouensis L. M. Gao.