Torreya jackii

Chun 1925

Common names

长叶榧树 chang ye fei shu [Chinese].

Taxonomic notes

Li and Jin (2007) assessed genetic variation in T. jackii and found low in-population diversity but high between-population diversity, with differences increasing with distance between populations. This suggests that extant populations have been separate for some time and that differences have arisen due to environmental variation and/or genetic drift.

Torreya jackii forms a natural hybrid with T. grandis, which is T. grandis var. jiulongshanensis. See T. grandis for discussion. Moreover, Wang et al. (2019) provide molecular evidence of extensive natural introgression between the two species within their zone of overlap. That overlap only exists because of historical introductions of T. grandis for cultivation; thus T. grandis threatens the genetic integrity of T. jackii, emphasizing the importance of ecological reserves for preservation of this species.

Type: China, Zhejiang, Xianju, R.C. Ching 1779, lectotype PE (accessed 2022.12.18).

Description

Evergreen dioecious shrubs or small trees to 12 m tall and 20 cm dbh with a thin, open crown of spreading, drooping branches. Bark flaky, pale brown, weathering dark gray. Twigs slender, long and flexible, with opposite branching in a horizontal plane at 30-60° angles, but sometimes more than 2 laterals from a node; round, grooved along leaf bases, green in first year, then reddish brown. Very small buds at ends of twigs; bud scales at terminal node of previous year larger, broad-triangular, keeled, deciduous. Leaves mostly drooping, linear, 35-70 × 3-4 mm with a 1-2 mm twisted petiole, abruptly widening at the base, coriaceous, lustrous green on adaxial (upper) surface with a proximal, slightly depressed midvein; lower surface with a stomatal band on either side of a prominent midrib, margins flat or slightly downcurved; apex cuspidate; stomatal bands 0.5-0.7 mm wide, gray to pale brown, the stomata randomly distributed. Pollen cones axillary, solitary, 5-8 × 4.5-5 mm, pale yellow at maturity. Seeds borne in axillary structures, paired, sessile, with rounded, keeled bract scales subtending the aril; the ripe aril fleshy, smooth, reddish yellow, with a whitish or glaucous bloom, obovoid, 20-30 × 10-12 mm, mucronate at apex (Farjon 2010).

The droopiness, both of the crown and the foliage, immediately distinguish this from other species of Torreya, but it does resemble Cephalotaxus fortunei; however this species has leaves twisted at the base (and other differences).

Distribution and Ecology

China: N Fujian, NE Jiangxi, and S Zhejiang (Fu et al. 1999), at elevations of 120-1320 m (Yang and Luscombe 2013). The climate is warm temperate to subtropical with annual precipitation of 1350-1600 mm, mainly from a summer monsoon, and a mean annual temperature of 17-20°C with minima above -10°C. Soils are acidic, siliceous, with pH 4.2-5. Habitat is evergreen broadleaf forest, usually on shady steep slopes or near streams, with no other common conifers (Farjon 2010). Hardy to Zone 8 (cold hardiness limit between -12.1°C and -6.7°C) (Bannister and Neuner 2001).

T. jackii has a conservation status of "endangered" due to rapid and ongoing habitat loss, primarily to agriculture, and related to overexploitation for timber (large trees are now nonexistent) and the tree's low elevation distribution, which puts it into a zone that has seen rapid loss of forest habitat in recent decades (Yang and Luscombe 2013). This assessment is corroborated by molecular evidence indicating that the species has experienced "a dramatic population collapse during the past 300 years, when anthropogenic disturbances also increased dramatically" (Tong et al. 2021). T. jackii is protected in the Jiangshi Nature Reserve in Fujian province, declared especially to protect this species, and it occurs in several other reserves across its range (e.g. Yukeng Nature Reserve in Zhejiang province); however its distribution is still incompletely known, which hampers conservation efforts (Yang and Luscombe 2013).

The roots have a fleshy cortex that can store enough water to enable drought tolerance (Farjon 2010). The species forms a vesicular-arbuscular mycorrhiza, which is typical in the Taxaceae (Lu et al. 2021).

Remarkable Specimens

No data as of 2023.02.23.

Ethnobotany

Both wood and leaves are very fragrant. The wood is used to make agricultural implements, utensils, and handicrafts (Fu et al. 1999). The species is rarely seen in ornamental use, and outside China is mainly found only in major botanical gardens.

Observations

Remarks

The epithet honors Chun's professor, John T. Jack of the Arnold Arboretum (Chun 1925).

Citations

Chun, W. Y. 1925. Two new trees from Chekiang. Journal of the Arnold Arboretum 6:144. Available: Biodiversity Heritage Library, accessed 2022.12.18.

Fu Liguo, Li Nan, and Robert R. Mill. 1999. Taxaceae. In Wu Zheng-yi and Peter H. Raven (eds.). Flora of China, Volume 4. Beijing: Science Press; St. Louis: Missouri Botanical Garden. This document is available online. Go to http://www.efloras.org, click on "Flora of China," and search for the taxon of interest by its scientific name.

Li Junmin and Jin Zexin. 2007. Genetic variation and differentiation in Torreya jackii Chun, an endangered plant endemic to China. Plant Science 172(5):1048-1053.

Lu, Y., Ma, Q., Chen, C., Xu, X., and Zhang, D. 2021. Effects of arbuscular mycorrhizal fungi on the nitrogen distribution in endangered Torreya jackii under nitrogen limitation. Planta 254(3):1-12.

Tong, Xin, Jian‐Hui Li, Kai Jiang, Yuan‐Yuan Li, Chao‐Nan Liu, Shekhar Biswas, Rong Wang, and Xiao‐Yong Chen. 2021. Back to the brink: Phylogeography and demographic history of the endangered Torreya jackii. Journal of Systematics and Evolution 60(5):1158-1171.

Wang, Y. J., Xiao, K., and Kou, Y. X. 2019. Torreya jackii (Taxaceae): a special species that is genetically admixed, morphologically distinct, and geographically sympatric with parent species. Forests 10(2):174. https://doi.org/10.3390/f10020174

Yang, Y. and D. Luscombe. 2013. Torreya jackii. The IUCN Red List of Threatened Species 2013: e.T32379A2816957. https://www.iucnredlist.org/species/32379/2816957, accessed 2022.12.18.

See also

Li, Hao, Yu Tang, Kai-Yuan Liang, Yi Zang, Ezzat EA Osman, Ze-Xin Jin, Jia Li, Juan Xiong, Junmin Li, and Jin-Feng Hu. 2022. Phytochemical and biological studies on rare and endangered plants endemic to China. Part XXII. Structurally diverse diterpenoids from the leaves and twigs of the endangered conifer Torreya jackii and their bioactivities. Phytochemistry 198:113161.

The species account at Threatened Conifers of the World.