Cephalotaxus harringtonii var. wilsoniana

Taiwan plum yew
Conservation status
Endangered  (IUCN 3.1)
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Gymnospermae
Division:	Pinophyta
Class:	Pinopsida
Order:	Cupressales
Family:	Taxaceae
Genus:	Cephalotaxus
Species:	C. harringtonii
Variety:	C. h. var. wilsoniana
Trinomial name
Cephalotaxus harringtonii var. wilsoniana (Hayata) Kitam.
Synonyms
Cephalotaxus sinensis subsp. wilsoniana (Hayata) Silba Cephalotaxus sinensis var. wilsoniana (Hayata) L.K.Fu & Nan Li Cephalotaxus wilsoniana Hayata

Cephalotaxus harringtonii var. wilsoniana, commonly known as Taiwan plum yew and Wilson plum yew, is an endangered variety of conifer endemic to Taiwan.

Taxonomy

Etymology

The genus name Cephalotaxus comes from the Greek "kephale", meaning head. The suffix taxus refers to the yew plant. Together these names mean "head yew" which is in reference to the flower structures that appear as tight clusters or heads. The needle like leaves resemble a yew thus the name "head yew". The common name plum yew comes from the cones that resemble a plum in both shape and color.

History

The Taiwan plum yew was originally considered as a variety of Cephalotaxus sinensis due to similar morphology, however DNA evidence suggests that it is more closely related to its Japanese cousin Cephalotaxus harringtonii. It has also been considered as a separate species. Currently, some authorities do not recognize the Taiwan plum yew as a distinct taxon, and consider it to be a synonym of the parent species.

Description

The foliage is similar to true yews. The leaves are arranged in a "v"-shaped linear row on the stem, and on the base of the stem the leaves are arranged in a spiral. The foliage is a rich green when mature. New shoots are a bright green and darken after three to four years.

Distribution and habitat

The Taiwan plum yew is endemic to the island of Taiwan where it grows in humus rich soil or gravel cliffs. They grow as small trees or bushes in the understories of wet subtropical forests or warm-temperate forests. This variety grows in mixed deciduous and evergreen forests and prefers locations with light to full shade. It is found at elevations of 1,500 to 2,000 meters.

Reproduction and dispersal

This variety is distinguished by the reproductive strobili. The seed of the plum yew is approximately the size of an olive or small plum and is larger than those of a true yew. The seed is enclosed by a hard, thin shell and a fleshy outer coat. The outer coat changes colors as the seed ripens from a blue-green to a rich red and finally to a purple-brown. Once it turns purple-brown the fleshy outside degrades causing it to detach from the seed.

This Taiwan plum yew is dioecious with the male and female strobili on different plants. Male strobili are created in clusters of anthers attached to a flat head. The anthers are about 0.25 inches in diameter and are arranged in the axils of the leaves. Female strobili develop in ovules. Often found in pairs of six to twelve, these ovules are attached to an oval, mauve colored cone which will start to expand at 0.5 inches up to 1.25 inches when matured. There is one mature seed per cone, and three to five female cones are grown on stalks near or at the end of the current or last year's branch. Female cones are wind-pollinated.

Seeds have a long maturation time, and the pollen cones usually take nine to eleven months from initiation to dispersal. Female cones take twenty-one months to mature from initiation.

Cultivation

Cultivation of the variety Cephaltaxus harringtonia var. wilsoniana is limited to a only a few nurseries.

Conservation

The variety is considered endangered due to habitat loss caused by logging, population fragmentation, and ground clearance to make room for plantations of Cryptomeria species. It is concentrated in the northern part of Taiwan where conservation is widespread.

Uses

The wood is used for fire and medicinal purposes. The seeds from female cones are also collected for oil. It is increasingly used in medicine due to the anticancer compounds found in the vegetative tissues and seeds. Experiments have been conducted with ester alkaloids, but no therapeutic applications have been announced.