Assessing patterns of morphological variation of Quercus spp. in mixed-oak communities

Cluster analyses and principal components analyses were used to evaluate phenetic relationships among Quercus coccinea, Q. falcata, Q. marilandica and Q. velutina in three mixed-oak communities in the Land Between the Lakes (Kentucky and Tennessee). Two sets of quantitative characters, taken from (1) leaves and (2) fruits and buds, were analyzed for each community. In addition, all OTUs were combined for analyses of the two data sets as well as for an analysis based on all characters. The results support the hypothesis that hybridization is occurring between Q. velutina and Q. coccinea and/or Q. marilandica. Although the leaf and fruit/bud data sets tend to yield the same patterns of overall similarity, there are distinct differences between complementary phenograms in each community. While all analyses indicate that Q. coccinea and Q. velutina are more similar to each other than to either of the other two taxa, the leaf and fruit/bud data sets do not agree on the phenetic similarities between Q. falcata, Q. marilandica, and the Q. coccinea-Q. velutina cluster. The patterns illustrated by these analyses provide insight into the characters emphasized in earlier hypotheses of taxonomic and/or evolutionary relationships among these species.