Variation in leaf morphology of Quercus crispula and Quercus dentata assemblages among contact zones: a method for detection of probable hybridization

I describe variation in leaf morphology of Quercus crispula and Quercus dentata assemblages within and among their contact zones. Such relationships provide a relatively fast and accurate method for detecting hybridization. Using discriminant function (DF) analysis based on leaf characteristics, I was able to differentiate between these two species in pure zones. In three of five contact zones, the DF scores showed broad, continuous distributions with three or more peaks. The trees showing intermediate leaf morphology are considered to be hybrids. In the other two contact zones, the DF scores showed distinct bimodal distributions, suggesting that Q. crispula and Q. dentata rarely hybridize in these sites. Thus, the method described in this study should be effective for detecting probable hybridization between these two species in contact zones, and the relative frequency of hybridization among contact zones. However, there was likely to be intraspecific variation of Q. crispula between geographic ranges, restricting interpretations to patterns occurring within sites or limited geographic ranges.