Tuesday, August 31, 2010

One Species: Wavyleaf Oak

I was struck by the description of wavyleaf oak, Quercus undulata Torr., as listed in Oaks of North America by Miller & Lamb.

LEAVES: deciduous or evergreen, thick and leathery, varying in size and shape but generally about 1.8 to 6.25cm long, wavy lobed or toothed...

FRUIT: acorn matures in 1 year, 1.5 to 2.1cm long, borne singly or in pairs, set shallowly or up to one-half in cup.

See any problems with the taxonomy of this "species?" Apparently you're not alone. To quote further from Oaks of N.A:

"Little, 1979 Checklist (of American Trees), has reduced Q. undulata Torr. to a hybrid of Q. gambelii with one of six other species. Over vast stretches of the range of Q. undulata, the only parent available is Gambel oak. Thus, it is difficult to see what other parent may have been available to produce a hybrid. For this reason it has been described as a species in this publication. However, the wide range of variation in size and shape of leaves and acorns across the range of this oak tends to strengthen the hybrid theory."

Yes, I should say it does. I give very little credence to the authors' contention that since Gambel oak is the only other oak present across large portions of the range of wavyleaf oak, it can't be a hybrid simply because no other oak species currently occupies a large portion wavyleaf oak's range.

We know that the ranges of many oaks have moved in response to changes in climate. Cottam identified a population of natural hybrids of Q. turbinella (scrub live oak) and Gambel oak in northern Utah, outside the current range of scrub live oak. Cottam theorized - no doubt correctly - that the range of scrub live oak advanced into northern Utah 7,500 years ago during a period in which the mean temperature was 4 degrees warmer than it is now. These scrub live oaks hybridized with Gambel oak, and then died out as temperatures cooled, leaving the hybrids behind.

... so there easily could have been another oak whose range migrated or expanded to intersect that of Gambel oak across a wide area, and this oak could easily be the other parent of wavyleaf oak. Or perhaps I should say these oaks (plural) could easily be the other parents of several "wavyleaf oak" hybrids. Again from Oaks of N.A:

Wavyleaf oak is considered to be the offspring of the following crosses:

Quercus x pauciloba (Q. gambelii x turbinella) - Aha there's our Cottam tree
Quercus x (no name given) (Q. gambelii x arizonica)
Quercus x (no name given) (Q. gambelii x grisea)
Quercus x (no name given) (Q. gambelii x havardii)
Quercus x (no name given) (Q. gambelii x mohriana)
Quercus x (no name given) (Q. gambelii x muelenbergii)

Good grief. Perhaps a better Linnaean name for wavyleaf oak is Quercus x I don't know what the hell it is.

We need a genome map to determine parentage... or a special arboreal episode of Maury Povich.
All I know for sure is that the same variation that makes oaks virtually impossible to classify into species and hybrids also hold the key to feeding mankind and saving our planet. If only we would devote 1/1,000,000th the time to breeding oaks that has been devoted to annual grains.

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