Remember the sniggering tales of the redheaded traveling salesman whose territory could be plotted in later years by redheaded children in various families not otherwise so blessed? Like the salesman, plant species are not always monogamous, many of them easily exchanging genes. The oaks, especially, are famous for their tendency to interbreed among the various species, and hybrids are common. There are lots of opportunities, too, with more than 150 species in Mexico and 58 species north of that country.
Most oaks in our Chihuahuan Desert region occur in the highlands,
though some flirt with the upper fringes of desert. One such is Scrub Oak, Quercus
turbinella. This tree readily hybridizes with Gambel Oak, common in our highlands
as well as farther north. So, what's the connection with the traveling salesman? In
northern Utah and central Colorado, hundreds of miles north of Scrub Oak's present
range, hybrids clearly indicate past indiscretions. Traveling north during the hottest
part of our current interglacial age, Scrub Oaks met, and consorted with, northern
Gambel Oaks before retreating again to the south.
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.
Leaves of Scrub Oak Quercus turbinella), Chihuahuan Desert Gardens. Photograph by A. H. Harris.