Amentotaxus (catkin-yew) description

Amentotaxus

Pilger 1917 (p. 41)

Common names

Catkin-yew; sui hua shan shu [Chinese].

Taxonomic notes

A genus of six species:

Although Page (in Kubitzki, Fam. Gen. Vasc. Pl. 1: 299-302. 1990) included it in the Cephalotaxaceae, molecular data place Amentotaxus sister to Torreya, which also resembles it in seed size, seed shape, and in usually having bilaterally symmetric clusters of pollen sacs (Fu et al. 1999). Cheng et al. (2000) corroborated this conclusion using chloroplast matK gene analysis, and separately using nuclear data (nrITS sequences). Various relatively recent authors have treated A. assamica, A. formosana, and A. hekouensis within A. argotaenia, and A. poilanei within A. yunnanensis. One more recent molecular study (Gao et al. 2016) has used multiple lines of molecular evidence to assess infrageneric relationships between A. argotaenia, A. formosana, A. hekouensis, and A. yunnanensis. That analysis placed an A. argotaenia + A. yunnanensis clade sister to an A. formosana + A. hekouensis clade, and based on morphological relationships, A. assamica would presumably fall into the former clade, and A. poilanei into the latter. It is entirely possible that molecular studies addressing all 6 species would alter these perceptions, though.

Description

Dioecious evergreen shrubs or small trees. Twigs opposite. Winter buds tetragonal-ovate, acute, glossy, scales decussate, in 3–5 whorls of 4, adaxially ridged. Leaves decussate, but brought into a single plane by twisting of petioles; blade straight to slightly falcate, usually >5 mm wide, adaxial surface mottled when fresh, rarely smooth, rugose or when dry, resin canal present below sheath of vascular bundle, sclereids present, rarely absent; base decurrent, margin slightly downcurved. Pollen cones are quite distinctive, aggregated into (1-)2–6(–10) long, slender, compound racemes or spikes arising on distal ends of branches; cones opposite, sessile or subsessile, ellipsoid or subglobose; microsporophylls numerous, shield-shaped; pollen sacs 3–8. Cones compressed-tetragonal or flattened abaxially, basal part with 6–10 pairs of decussate bracts arranged in 4 rows each of 3–5 bracts; ovule 1, sessile, erect. Seed ripening in 1st year, long pedunculate, ellipsoid or obovoid-ellipsoid, enclosed except for apex in a saclike aril that turns bright red or reddish-yellow when ripe; bracts persistent at base (Fu et al. 1999).

Distribution and Ecology

China, India, Laos, Vietnam and Taiwan (Farjon 1998, Averyanov et al. 2014). All taxa are listed by the IUCN as of conservation concern, being either "vulnerable" or "endangered", due chiefly to small populations, habitat loss, and ongoing population declines. They primarily grow in the understory of moist submontane and montane semi-deciduous and evergreen forest (Gao et al. 2017).

Distribution data from GBIF (2022). Note that the GBIF database only contains reliable locations for four species. A. argotaenia is red, A. formosana is orange, A. poilanei is yellow, and A. yunnanensis is green.

Remarkable Specimens

There are no data for species other than A. formosana, which achieves 36 cm dbh and 10 m tall, and 126 years of age.

Ethnobotany

Several species have limited, local use for their wood or as ornamentals. Outside of their native range, Amentotaxus is seldom seen except in major botanical gardens or arboreta, where it is cultured indoors or in tropical to warm-temperate climates.

There have been no dendrochronological studies for species other than A. formosana, which has been used in one study of population growth and age structure.

Observations

See the species accounts.

Remarks

The name Amentotaxus is derived from Taxus, recognizing its status in the yew family; and the Latin amentum, string, recognizing the distinctive racemes of pollen cones.

Citations

Averyanov, L.V., Nguyen, T.H., Sinh, K.N., Pham, T.V., Lamxay, V., Bounphanmy, S., Lorphengsy, S., Phan, L.K., Lanorsavanh, S., and Chantthavongsa, K. 2014. Gymnosperms of Laos. Nordic Journal of Botany 32(6):765–805. doi:10.1111/njb.00498.

Cheng Yuchang, Robert G. Nicolson, Kim Tripp, and Shu-Miaw Chaw. 2000. Phylogeny of Taxaceae and Cephalotaxaceae genera inferred from chloroplast matK gene and nuclear rDNA ITS region. Molecular Phylogenetics and Evolution 14(3):353–365.

Gao L.M., Y. Li, L. K. Phan, L. J. Yan, P. Thomas, K. P. Long, M. Möller, and D. Z. Li. 2016. DNA barcoding of East Asian Amentotaxus (Taxaceae): Potential new species and implications for conservation. Journal of Systematics and Evolution 55(1):16–24.

Pilger, R.K.F. 1917. Kritische Übersicht über die neuere Literatur betreffend die Familie der Taxaceae. Botanische Jahrbücher für Systematik, Pflanzengeschichte und Pflanzengeographie. 54:1-43. This publication is available online at botanicus.org.