Filling a Gap in Quercus Phylogeny: Molecular Phylogenetic Evidence, Morphometric and Biogeographic History of Quercus petraea subsp. pinnatiloba Matt. Liebl from Türkiye

Quercus petraea subsp. pinnatiloba is a narrowly distributed oak taxon in southeastern Türkiye, and its taxonomic position has long remained uncertain. This study aims to clarify its distinctiveness by integrating morphological, molecular, and biogeographical evidence. Principal Component Analysis (PCA) and Stepwise Discriminant Analysis (SDA) of 14 leaf traits revealed that subsp. pinnatiloba constitutes a morphologically stable and distinctly differentiated group from other Q. petraea subspecies and closely related taxa, characterized by key diagnostic traits such as petiole length (PL), lamina length (LL), length of leaf blade at its broadest point (WP), and lobe width at the tip of the widest lobe (LW). Phylogenetic analyses based on nuclear ITS and plastid markers (rbcL, psbA-trnH) confirmed its placement within sect. Quercus, yet consistently distinguished it genetically from other subspecies for the first time. Molecular dating (BEAST) suggested divergence in the Miocene (11 Mya with 95% HPD 3.01, 20.95) while RASP biogeographical analysis indicated an origin in the Euro-Siberian region with later dispersal into the Mediterranean. These integrative results support its recognition at species rank as Quercus pinnatiloba, clarifying its phylogenetic placement and underscoring the conservation importance of this lineage.