Phylogenetics PG_J0009

Title : An overview of Quercus: classification and phylogenetics with comments on differences in wood anatomy
Author :  Kevin C. Nixon
Year Publish : 2007
Place of Publish : texasoakwilt.org
Abstract :

The oaks (genus Quercus) are one of the most important groups of flowering plants and
dominate large regions of the northern hemisphere. They are most prevalent in subtropical,
temperate, and montane tropical regions. Quercus is phylogenetically divided into at least five
major groups, of which three (the red oaks, white oaks, and intermediate oaks) are native to the
New World. Overall, there are more than 200 species of oak in the Western Hemisphere, and
probably a larger number in Asia, and relatively few in Europe. The center of diversity in the
Americas is in the highlands of Mexico, with a secondary center in the southern United States.
From the standpoint of susceptibility to disease, the phylogenetic groupings have some
predictive capability, and in some cases this may be related to differences in ecology,
physiology, and wood anatomy. White oaks in general are more diverse in the drier parts of
North America, and have heartwood that is typically blocked by tyloses, while red oaks generally
have fewer tyloses. Because tyloses block water flow through the heartwood, white oak wood
makes good wine barrels while red oak wood does not. Given the greater susceptibility of red
oaks to both oak wilt and sudden oak death (SOD), these differences in wood anatomy may be
relevant