Morphology, geometric morphometrics, and taxonomy in relict deciduous oaks woods in northern Italy

The Euganean Hills are a well-known refugee site for thermophilous woody flora in northern Italy. Among the species recorded here, there is Quercus dalechampii. The Euganean Hills are the only northern Italy site where the occurrence of this oak species is considered. The aim of this paper was to verify the presence of Q. dalechampii in the study area and to select possible diagnostic morphological traits that are usable to distinguish it from Q. petraea and Q. pubescens . Forest stands dominated by Q. petraea, Q. pubescens, and the presumed Q. dalechampii were sampled using the phytosociological approach to highlight their ecological features. Leaf and fruit material from 104 oak individuals was analysed from a macro-morphological and micro-morphological point of view. Leaf shape was also analysed using the geometric morphometric approach. All multivariate analysis procedures applied on the matrices of leaf and fruit traits highlighted two main clusters of morphological diversity. One was restricted to Q. pubescens individuals, and the other one was a mix of Q. petraea and presumed Q. dalechampii individuals. According to the twig and leaf trichome traits, all presumed Q. dalechampii individuals were classified as belonging to the Q. petraea collective group. Morphological differences between Q. petraea and presumed Q. dalechampii were considered not significant. In conclusion, the occurrence of a third oak species, in addition to Q. petraea and Q. pubescens, was not confirmed for the study area by the results of this paper. Graphic abstract