Taxus floridana

Taxus floridana
Conservation status
Critically Endangered  (IUCN 3.1)
Imperiled  (NatureServe)
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Gymnospermae
Division:	Pinophyta
Class:	Pinopsida
Order:	Cupressales
Family:	Taxaceae
Genus:	Taxus
Species:	T. floridana
Binomial name
Taxus floridana Nutt. ex Chapm.
Natural range

Taxus floridana, the Florida yew, is a species of yew, endemic to a small area of the Apalachicola River. This species is has restricted extent of occurrence (EOO) of 24km along the Apalachicola River and resides in the mesophytic forests of northern Florida at altitudes of 15–40 m. It is listed as critically endangered and is protected in reserves at the Torreya State Park and at the Nature Conservancy's Apalachicola Bluffs and Ravines Preserve. The Florida yew has legal protection under the United States and Florida Endangered Species laws. This species is considered endangered because of how rare it is and its limited range.This article writes about the description and ecology of the Florida yew, as well as discusses the ongoing threats and conservation attempts.

Description

It is an evergreen coniferous shrub or small tree growing to 6 m (rarely 10 m) tall, with a trunk up to 38 cm diameter. The bark is thin, scaly purple-brown, and the branches are irregularly orientated. The shoots are green at first, becoming brown after three or four years. The leaves are thin, flat, slightly falcate (sickle-shaped), 1–2.9 cm long and 1–2 mm broad, with a bluntly acute apex; they are arranged spirally on the shoots but twisted at the base to appear in two horizontal ranks on all except for erect lead shoots. Individuals typically occur in clumps and are multi-stemmed with varying stem densities . It is dioecious, with the male and female cones on separate plants; the seed cone is highly modified, berry-like, with a single scale developing into a soft, juicy red aril 1 cm diameter, containing a single dark brown seed 5–6 mm long and occur singly on few leaf axils. The pollen cones are globose, 4 mm diameter, produced on the undersides of the shoots in early spring.

It occurs in the same region as the also-rare Torreya taxifolia and is similar to it in general appearance, but can be differentiated by the shorter, blunt-tipped (not spine-tipped) leaves and the less strong smell of the crushed leaves. Distinction from other yew species is more difficult, and like most yews it has sometimes been treated as a subspecies of Taxus baccata, as T. baccata subsp. floridana (Nutt. ex Chapm.) Pilger.

Ecology

Taxus floridana grows slowly, and prefers slightly acidic, well drained soil and partial shade. It is highly fire sensitive as well as shade tolerant. Potential influences on their distribution include variation of soil, aspect, and moisture. There is no indicator species associated with it. It is hardy to USDA zone 8. It can be grown from cuttings or seeds. Seed scarification is required for germination and it persists through layering and sprouting. Birds feed on their cones and excavate stems for insects.

Uses

The bark contains paclitaxel, a mitotic inhibitor used to combat numerous forms of cancer. The inhibitor is called Taxol, but scientists have found new evidence that suggests the Taxol is actually produced by the fungus that lives on the Florida yew.(add citation here) The seeds and leaves, however, are poisonous to humans if consumed.

Threats

There are a multitude of threats to the Florida yew.

The ripened cones of the tree are an important food source to many bird species and they have been reported to consume almost all of these cones. Beavers like to chew off the tops of young stems and White-tailed deer rub themselves on the trees and browse particularly on small stems. With increasing populations, these deer could pose more of a threat in the following years. This species is also highly sensitive to fire. There are a couple of populations located on unprotected private lands, which are particularly susceptible. Logging and Urban development are potential threats to the few existing populations. The mortality rate of the adult trees is higher than the recruitment which has led to a rapid decline. Selective logging as led to a decline in soil fertility and due to the sensitivity of this species, has caused poor recruitment levels. Threats of habitat degradation and reduced regeneration capabilities are the most prominent issue, which have resulted in no new recruitment in the past few decades, greatly affecting population demographics.

The biggest threat to the survival of this species is the low levels of recruitment, the cause of which has still not been identified.

Conservation

Many populations reside in protected areas and this helps to protect the species against human interference. However this also means that there are more animal populations who can prey on the tree. Many studies have been performed on the Florida Yew, particularly looking at the survival and recruitment of seeds. There are ongoing propagation studies and studies on this species reproductive biology to better understand the decline in recruitment.