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Encyclopedia > Taxaceae
Taxaceae - Yew family

A fleshy aril partly surrounds each seed in the
yews; note also immature cones with seed
not yet surrounded by the aril
Scientific classification
Kingdom: Plantae
Division: Pinophyta
Class: Pinopsida
Order: Pinales
Family: Taxaceae
Genera

Taxaceae sensu stricto
Taxus
Pseudotaxus
Austrotaxus

Cephalotaxaceae
Torreya
Amentotaxus
Cephalotaxus


The family Taxaceae, commonly called the yew family, includes three genera and about 7 to 12 species of coniferous plants, or in other interpretations (see Classification, below), six genera and about 30 species.


They are much branched, small trees and shrubs. The leaves are evergreen, spirally arranged, often twisted at the base to appear 2-ranked. They are linear to lanceolate, and have pale green or white stomatal bands on the undersides. The plants are dioecious, rarely monoecious. The male cones are 2-5 mm long, and shed pollen in the early spring. The female cones are highly reduced, with just one ovuliferous scale and one seed. As the seed matures, the ovuliferous scale develops into a fleshy aril partly enclosing the seed. The mature aril is brightly coloured, soft, juicy and sweet, and is eaten by birds which then disperse the hard seed undamaged in their droppings.


Classification

Enlarge
Phylogeny of the Taxaceae and Cephalotaxaceae - note that both groups have evolved from within the other conifers

The Taxaceae is now generally included with all other conifers in the order Pinales, as DNA analysis has shown that the yews are monophyletic with the other families in the Pinales (Chase et al., 1993; Price, 2003), a conclusion supported by micromorphological studies (Anderson & Owens, 2003). Formerly they were often treated as distinct from other conifers by placing them in a separate order Taxales.


The genera Torreya and Amentotaxus, previously included in this family, are better transferred to the Cephalotaxaceae, as genetic tests show they are more closely related to Cephalotaxus than to Taxus. Alternatively, they may be included, with Cephalotaxus, in a broader interpretation of Taxaceae as a single larger family (Price, 2003). In this sense, the Taxaceae includes six genera and about 30 species.


The differences between the Taxaceae and the Cephalotaxaceae are as follows:

Family  Taxaceae   Cephalotaxaceae 
 Cone aril   partly encloses seed   fully encloses seed 
 Cone maturation   6-8 months  18-20 months
 Mature seed length   5-8 mm *  12-40 mm

* To 25 mm in Austrotaxus


A few botanists have transferred Austrotaxus to its own family, the Austrotaxaceae, suggesting it may be closer to the Podocarpaceae than to the other Taxaceae, but genetic evidence does not support this transfer.


References

  • Anderson, E. & Owens, J. N. (2003). Analysing the reproductive biology of Taxus: should it be included in Coniferales? Acta Hort. 615: 233-234. (conclusion is 'yes')
  • Chase, M. W. et al. (1993). Phylogenetics of seed plants, an analysis of nucleotide sequences from the plastid gene rbcL. Ann. Missouri Bot. Gard. 80: 528-580.
  • Price, R. A. (2003). Generic and familial relationships of the Taxaceae from rbcL and matK sequence comparisons. Acta Hort. 615: 235-237.

Links to other Pinophyta families

Pinaceae | Araucariaceae | Podocarpaceae | Sciadopityaceae | Cupressaceae | Cephalotaxaceae | Taxaceae

  Results from FactBites:
 
Plant Systematics: Taxaceae (444 words)
The Taxaceae family is comprised of 5 genera made up of 20 different species.
Taxaceae tend to grow in damp valley bottoms where leaf littler accumulates.
The Taxaceae have recently been removed from the order coniferales (because their seeds are not borne in cones) and placed (the only family) in the order Taxales.
Pinophyta at AllExperts (1589 words)
The most commonly seen in the past was a split into two orders, Taxales (Taxaceae only) and Pinales (the rest), but recent research into DNA sequences suggests that this interpretation leaves the Pinales without Taxales as paraphyletic, and the latter order is no longer regarded as distinct.
Taxaceae: the fleshy aril which surrounds each seed in the European Yew (Taxus baccata) is a highly modified seed cone scale
In the families Podocarpaceae, Cephalotaxaceae, Taxaceae, and one Cupressaceae genus (Juniperus), the scales are soft, fleshy, sweet and brightly coloured, and are eaten by fruit-eating birds, which then pass the seeds in their droppings.
  More results at FactBites »

 
 

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