Phylogenetic relationships of Corylus species (Betulaceae) based on nuclear ribosomal DNA ITS region and chloroplast matK gene sequences

The phylogenetic relationships of 29 genotypes representing 12 species of the genus Corylus (Betulaceae) were investigated using sequences of the internal transcribed spacer regions of the nuclear ribosomal DNA and the chloroplast matK gene. The two genes gave different results. The ITS region in Corylus yielded only 22 informative characters. Nevertheless, several clades in Corylus were resolved: the shrub species C. avellana, C. maxima, C. americana, and C. heterophylla; another group of shrub species C. cornuta, C. californica, and C. sieboldiana; and the tree species C. colurna, C. chinensis, and C. jacquemontii which formed a paraphyletic group. Corylus ferox formed the basal-most branch of the Corylus clades. The strict consensus tree was congruent with the results of interspecific hybridization relationships and morphological classification. The matK sequence yielded only 10 informative characters. Two clusters appeared on the strict consensus tree, one with Asian and European species, and the other with North American species. However, this classification based on matK sequences was not in agreement with currently accepted taxonomic classification, and the paucity of informative characters precludes more definitive inferences from the matK data.