Quercus welshii is geographically restricted to the Navajo Basin area of NE Arizona and SE Utah. Two hypotheses have been formed in order to explain how Q. welshii evolved. One states that Q. welshii is a relic population left over from when its ancestor, Q. havardii, populated the region. The other states that Q. welshii is stabilized hybrid of Q. gambelii and Q. turbinella, the two dominate species in the area. In order to test if Q. welshii is a hybrid or relic population, both genetic and morphological data was gathered from sample populations. Analysis showed that Q. welshii possesses its own genetic signature, lending evidence in support of the theory that Q. welshii is a relic population. The data also showed that Q. welshii is not morphologically a hybrid of Q. turbinella and Q. gambelii, but has its own distinct phenotype.
