A morphometric study of Quercus crenata Lam. species complex (Fagaceae).

Plants ascribed to the complex Quercus crenata - Q.pseudosuber, supposed to be hybrids Q.cerris x Q.suber, grow sympatric with both parental species in peninsular Italy and Sicily, but they also occur in the Alpes Maritimes, in northern Italy, in Slovenia and Istra, where Q.suber is absent. To test whether northern and southern plants of this complex should be regarded as different taxa, a morphometric survey was done on 91 specimens. Based on 36 morphological characters of the leaf and fruit, the northern and southern specimens did not form distinct aggregates in a principal components analysis (PCA), but they could be segregated in a discriminant analysis. PCA ordination plots further indicated that the southern specimens are morphologically more variable. Indeed, when tested individually, the means of six characters differed significantly between the two parts of the distribution range, and 12 characters were significantly more variable in southern plants. Based on our results, we propose that the two sets of plants are taxonomically distinct. The "southern" plants are hybrids inter parentes, for which we propose to maintain the name Quercus x pseudosuber Santi. The "northern" plants with reduced variability are possibly relicts of ancient hybridization and to them properly applies the name Quercus crenata Lam.