Is Quercus virgiliana a distinct morphological and genetic entity among European white oaks?

The existence of Quercus virgiliana Ten. is a subject of debate among botanists and silviculturists. It was considered a distinct species, sometimes as an intraspecific taxonomic unit of Q. pubescens L., or was not even recognized as a taxon or infrataxon. This disagreement with regard to the taxonomic classification is explained by the morphological similarities between Q. virgiliana and Q. pubescens, with a small overlap between particular leaf and fruit traits. The main objective of this study was to evaluate the macromorphological fruit and leaf descriptors in Romanian populations of pubescent oaks. We wanted to find which traits discriminate between the 2 taxa. By using 7 microsatellite markers, we checked whether the 2 taxa have different genetic structures. A total of 918 individuals were sampled for morphological analyses from 20 stands across Romania. The length of cupula peduncle showed the highest discriminating power, but also leaf characters such as abaxial laminar pubescence, lamina length, sinus width, and length of lamina at largest width helped to discriminate between the 2 taxa. The analysis performed at 7 microsatellite loci revealed very little genetic differentiation between Q. pubescens and Q. virgiliana. Different genetic assignment tests provided no support for 2 genetic entities in our sample. This could be explained by the restricted number of loci used. However, the morphological differences found in this study suggest that Q. virgiliana is an intraspecific taxonomic unit of Q. pubescens rather than a distinct species.