Evidence from multivariate morphometric study of the Quercus pubescens complex in southeast Italy

The name Quercus pubescens s.l. encompasses a complex of deciduous oak taxa with mainly southeast-European distribution and a large ecological niche. As the easternmost region of Italy, Apulia is rather isolated from a geographical and physiographical viewpoint and counts the highest number of oak species (10). In the taxonomic and phytosociological literature, the occurrence of several species belonging to the Quercus pubescens collective group is reported for this region. In order to verify if different sets of morphological characters are associated with different taxa, 24 populations of Quercus pubescens s.l. located in different ecological-geographical areas of Apulia were sampled.
A total of 367 trees, 4254 leaves and 1120 fruits were collected and morphologically analysed.
Overall, 25 morphological characters of oak leaves and fruits were statistically treated using both univariate and multivariate analysis. Nested ANOVA showed that leaves collected from a single tree exhibited a degree of morphological variability higher than that observed when comparing leaves coming from different trees of the same population and from different trees of different populations as well. Almost all the morphological characters analysed exhibited a continuous trend of variation so that none of them can be used as a character to discriminate between populations. Only leaf and fruit “size” and fruit petiole length emerged as slightly discriminating characters. Our results suggest that it is unlikely that more than one species belonging to the Quercus pubescens complex occurs in the Apulia region. Comparison between the Apulian populations and a genetically pure Q. pubescens population coming from a different area (the Molise region) strengthened the assumption as to the existence of a single species that can provisionally be classified under the name of Q. pubescens s.l.