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Torreya is a genus of conifers comprising five or six species, treated in either the Cephalotaxaceae, or in the Taxaceae when that family is considered in a broad sense. Four are native to eastern Asia, the other two native to North America. They are small to medium sized evergreen trees reaching 5-20 m, rarely 25 m, tall.

The leaves are spirally arranged on the shoots, but twisted at the base to lie in two flat ranks; they are linear, 2-8 cm long and 3-4 mm broad, hard in texture, with a sharp spine tip.

Torreya can be either monoecious or dioecious; when monoecious, the male and female cones are often on different branches. The male (pollen) cones are 5-8 mm long, grouped in lines along the underside of a shoot. The female (seed) cones are single or grouped 2-8 together on a short stem; minute at first, they mature in about 18 months to a drupe-like structure with the single large nut-like seed 2-4 cm long surrounded by a fleshy covering, green to purple at full maturity. In some species, notably the Japanesemarker Torreya nucifera (Kaya), the seed is edible. Natural dispersal is thought to be aided by squirrels which bury the seeds for a winter food source; any seeds left uneaten are then able to germinate.

The genus is named after the American botanist John Torrey.

Torreya californica (California Torreya) is endemic in Californiamarker. It is the largest species, reaching 25 m tall.

Torreya taxifolia (Florida Torreya, aka Gopher Wood) has a restricted habitat within Torreya State Parkmarker, along the east bank of the Apalachicola Rivermarker in the Florida Panhandle and immediate adjacent southernmost Georgiamarker. It is an endangered species, which has suffered a major decline in numbers due to fungal disease (possibly Phytophthora). Elvy E. Callaway claimed that it was the "gopher wood" used to build Noah's Ark. Post-glacial global warming has also been implicated in this species' decline; however, it is sold by at least one Florida nursery in Hudsonmarker, well south of its native range. It is best adapted to the cooler, moister climate found in this area during the last ice age but, due to poor dispersal abilities, has not been able to colonise further north in the post-glacial warming. Cultivated specimens are however growing very well in cooler climates in the Appalachian Mountainsmarker, in northern Georgia and at the Biltmore Gardensmarker in Asheville, North Carolinamarker where it is regenerating naturally. It has been proposed that the best course to save the species from extinction is to plant groves of it in these areas. Called "assisted migration", intentional movement of a plant outside of its historical range (though perhaps consistent with its deep-time range) became an important issue in the conservation community in 2007 and 2008, with Torreya taxifolia (Florida Torreya) being the featured plant (see Further Reading below).

Further reading

Fox, Douglas. 2007. When worlds collide. Conservation 8(1):28-34.

Nijhuis, Michelle. 2008. Taking Wildness in Hand: Rescuing Species. "Orion Magazine" May/June 2008, pp. 64-78.

Torreya Guardians has a webpage devoted to hotlinks for following the proposals and news on assisted migration and rewilding: "Assisted Migration Hotlinks".

References




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