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ŠUMARSKI LIST 5-6/2018 str. 38     <-- 38 -->        PDF

members of the Ilex infrageneric group, Q. ilex and Q. coccifera, was evident. Finally, the rooted consensus cluster network clearly indicated close relationships between all members of the Cerris subclade, and further suggested the hybrid origin of the Q. × viridis with Q. suber as one of the parental species (Figure 5).
Our work represents the first attempt to resolve the taxonomic status of the “green oak” (Q. × viridis), described by Trinajstić (1974a) as a putative hybrid between Q. cerris and Q. ilex, based on molecular data. We used both plastid and nuclear DNA sequences to carry out a phylogenetic analysis involving a total of nine oak taxa from a wide geographic range surrounding the investigated oak, including all possible parental species. All our results of phylogenetic relationships among the studied oak taxa do not support Q. ilex as one of the parental species of the green oak. Rather, they confirm that the investigated green oak individuals are actually Q. crenata Lam., a presumed hybrid between Q. cerris and Q. suber, as first suggested by Jedlowski (1955). However, the two putative Q. × viridis individuals included in this study did not show identical phylogenetic pattern.
Both putative Q. × viridis individuals shared the same cpDNA haplotype (Figure 3) which was also present in all other cerroid oaks included in this study (Q. cerris, Q. suber and Q. crenata). This is however not surprising as the used cpDNA barcoding regions (trnK-matK and trnH-psbA) were shown to have low differentiation rates below the infrageneric level and thus relatively low efficiency to discriminate between closely related Quercus taxa, particularly for the Group Cerris (Simeone et. al., 2013). Interspecific sharing of plastid haplotypes is also well documented for the white oaks of the infrageneric groups Quercus and Ilex across wide geographic areas (Petit et. al., 2002; Slade et. al., 2007; Vitelli et al., 2017).
On the other hand, the nuclear 5.8S + ITS2 region has shown to have a better discriminatory power in oak phylogeny compared to the used plastid regions (Bellarosa et. al., 2005). In this study, the two Q. × viridis individuals displayed slightly different ribotypes, separated by only one mutational step (Figure 3). In addition, the “famous” green oak