Pilgerodendron

Pilgerodendron
Conservation status
Vulnerable  (IUCN 3.1)[1]
CITES Appendix I (CITES)[2]
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Gymnospermae
Division:	Pinophyta
Class:	Pinopsida
Order:	Cupressales
Family:	Cupressaceae
Subfamily:	Callitroideae
Genus:	Pilgerodendron Florin
Species:	P. uviferum
Binomial name
Pilgerodendron uviferum (D.Don) Florin
Synonyms[3]
Juniperus uvifera D.Don Libocedrus uvifera (D.Don) Pilg. Thuja tetragona Hook. Libocedrus tetragona (Hook.) Endl.

Pilgerodendron is a genus of conifer belonging to the cypress family Cupressaceae.^[3] It has only one species, Pilgerodendron uviferum, which is endemic to the Valdivian temperate rain forests and Magellanic subpolar forests of southern Chile and southwestern Argentina. It grows from 40 to 54°20' S in Tierra del Fuego, where it is the southernmost conifer in the world.^[4][5] It is a member of subfamily Callitroideae, a group of distinct Southern Hemisphere genera associated with the Antarctic flora.^[6][7]

Pilgerodendron is very closely related to the New Zealand and New Caledonian genus Libocedrus, and many botanists treat P. uviferum within this genus, as Libocedrus uvifera (D.Don) Pilg.^[8] It is also a taxonomical synonym for Libocedrus tetragona (Hooker).^[9] The species is known locally as ciprés de las Guaitecas^[10] (after the Guaitecas Archipelago), and elsewhere by its scientific name, as pilgerodendron. The genus is named after Robert Knud Friedrich Pilger.^[6]

P. uviferum is a dioecious, slow-growing, narrowly conical evergreen tree that grows from 2–20 m in height, with a trunk up to 1.5 m in diameter. Taller specimens and wider trunks (reportedly up to 3 m in diameter) are known to have existed before it was overexploited. The leaves are scale-like and arranged in decussate pairs, with each leaf equal in size, giving the shoots a square cross-section (unlike the Libocedrus species, where pairs of larger leaves alternate with pairs of smaller leaves, giving a somewhat flattened shoot). The seed cones are 5–12 mm long and 4–6 mm broad, with four scales, two sterile basal scales and two fertile scales; each scale has a slender spine-like bract, and each fertile scale has two winged seeds 3–4 mm long. The pollen cones are 5–10 mm long and 2 mm broad, with 12–20 scales.^[6][7]

It is found in the evergreen coastal lowland forests along the Pacific coast of southern Patagonia, in association with the broadleaf evergreens Nothofagus betuloides and Drimys winteri. It is also found in open stands in sheltered bogs farther inland, where it is often locally dominant, and ranges as far as the eastern slopes of the Andes in southwestern Argentina.^{[6][verification needed]} Forest dominated by Pilgerodendron are known as cipresales.^[11] The forests are common in the southern half of Chiloé Island where occupy many of flattish areas.^[11] At the northern end of its range it is found in association with Fitzroya cupressoides.^[6] The northernmost natural stands are found in 39°50' in the vicinity of the city of Valdivia.^[4] The conservation status of P. uviferu, in the far north of its natural distribution is poor, being fragmented by exotic plantations, threatened by livestock and having been decimated by lumberjacks and wildfires in the past.^[4] It has also been planted along the northern part of the Pacific Coast of the United States.^[12]

At present much Pilgerodendron uviferum grow in the Andes and in the Chilean Coast Range. However, during the interstadials of the region's last glacial period, P. uviferum grew in lowland areas such as the Central Valley, where it is now absent.^[13] Remaining lowland populations are thought to be relicts that have survived the warmer climate of the Holocene.^[13]

The wood of P. uviferum is yellow-reddish and has a distinct spicy-resinous smell, and is highly resistant to decay, which has made it very valuable as a source of timber for building construction in its native range. Much of its original lowland habitat has been cleared for this and other reasons.^[6][14] Due to over-exploitation, the species is now much scarcer than formerly, and is accordingly listed under CITES Appendix I, meaning commercial international trade is prohibited.^[2] P. uviferum is considered threatened by the World Conservation Monitoring Centre and vulnerable by the International Union for Conservation of Nature.