A new species Amentotaxus hekouensis L.M. Gao is described as new to science from Hekou, Yunnan of China, Lao Cai of Vietnam and Xiang Khouang of Laos. The new species is similar to A. argotaenia (Hance) Pilg. in linear or linear-lanceolate leaves, stomatal bands white and microsporophylls 6–8, each with 4–6 pollen sacs, but differs from the latter by its larger leaf size with 8–12.5 cm × 0.9–1.4 cm (vs. 2–11 cm × 0.5–1.1 cm in A. argotaenia), long acuminate leaf apex (vs. rounded to sharply triangular in A. argotaenia), stomatal bands with 25–30 rows (vs. 15–25 rows in A. argotaenia), stomatal bands equal to or slightly narrower than marginal bands (vs. narrower than marginal bands in A. argotaenia); pollen-cone racemes borne 1–2 (vs. 2–4 (10) in A. argotaenia), cones in 12–16 pairs (vs. ca. 12 pairs in A. argotaenia). Its distinctive nature has also been confirmed through DNA barcoding analysis of this genus. The new species is provisionally assessed as endangered (EN) due to its restricted distribution, small population size and the prevalence of habitat destruction within its range.

Amentotaxus hekouensis, New species, Endangered species, DNA barcoding, China

Amentotaxus Pilg. (Taxaceae), comprising of five or six species, is confined to southern China (including Taiwan), small areas of the eastern Himalayas and parts of Indo-China (Farjon 2010). All species of Amentotaxus are currently assessed as threatened at either national or global level (Wang and Xie 2004; IUCN 2016a). They usually occur in the understorey of moist submontane and montane semi-deciduous or evergreen forests (Gao et al. 2017). Amentotaxus argotaenia Pilg. is the most widespread species in this genus, recorded from most provinces of southern China as well as several areas of Vietnam and Laos (Fu et al. 1999; Farjon 2010; Nguyen et al. 2004; Averyanov et al. 2014). Amentotaxus yunnanensis H.L. Li is generally confined to the evergreen forests in the karst formation of southeast Yunnan, southwest Guizhou and adjacent areas of Vietnam and Laos (Fu et al. 1999; Farjon 2010; Averyanov et al. 2014). In 1996, A. hatuyenensis T.H. Nguyen was described from a single locality in Hagiang Province, northern Vietnam (Nguyen and Vidal 1996), but it is now regarded as a synonym of A. yunnanensis, based on morphological and molecular data (Phan et al. 2014; Gao et al. 2017). The remaining accepted species are restricted to Taiwan of China, eastern Himalayas and central Vietnam.

In September, 2006, specimens of an Amentotaxus tree were collected from limestone montane forest near Longyinchong village, Nanxi town, Hekou county, Yunnan province, China. Its morphology differed markedly from A. yunnanensis which commonly occurs in this region. In 2012, a second collection with the same morphology was found in the same region. In our DNA barcoding study (Gao et al. 2017), specimens from Hekou formed a distinct clade with specimens with similar morphology from Lao Cai in Vietnam and Xiang Khoang in Laos. The putative new species differs from all other recognised species in the length and width of the leaves, the shape of the leaf apex, curvature of the leaf margin, stomatal band width and its ratio to the leaf marginal bands. In 2016, several further surveys collected specimens with male cones that showed differences in the number of pollen sacs and the length of the racemes. Data analysis of trnL-F and ITS sequences for the newly collected specimen GLM-164271 had an identical sequence with the specimen GLM-06209 (Am 20) and CKF250 (Am 24), used in our DNA barcoding study (Gao et al. 2017), lending further support to the recognition of a new species (Figure 1). Although female cones have not yet been collected, other species in the genus do not show significant differences in the female cones (Fu et al. 1999; Farjon 2010).

Figure 1. 

Neighbour-joining (NJ) tree of ITS and trnL-F sequences of Amentotaxus based on P-distance with bootstrap values above 50%.

All measurements of the new Amentotaxus species were taken from dried herbarium specimens and field notes. In the description, length and width are represented as length × width. In total, eleven dried specimens of the new species were examined. All measurements of A. argotaenia (Hance) Pilg. and A. yunnanensis H.L. Li were based on literature (Fu et al. 1999; Farjon 2010) and our observations.

Amentotaxus hekouensis has distinct morphological features compared to the closely related A. argotaenia and the sympatric A. yunnanensis (Table 1). Its distinctive nature has also been supported by DNA barcoding analysis of this genus (Figure 1). Therefore, the description of a new species is supported by both morphological and molecular evidence. Due to its restricted distribution, small population size and the prevalence of habitat destruction within its range, A. hekouensis is assessed as endangered (EN).

We are grateful to Ms. Ling Wang from KUN for drawing the illustration of the holotype. We also thank Profs. Xun Gong, Yumin Shui from Kunming Institute of Botany, Chinese Academy of Sciences for providing the specimens from Laos and Vietnam of the new species. This work was supported by the Large-scale Scientific Facilities of the Chinese Academy of Sciences (Grant No: 2017-LSFGBOWS-02), the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB31010000), and the Program of Science and Technology Talents Training of Yunnan Province, China (Grant No: 2017HA014). The Royal Botanic Garden Edinburgh is funded by the Rural and Environment Science and Analytical Services division of the Scottish Government.