Abstract
Molecular diversity analysis of deciduous pubescent oaks was conducted for populations from Calabria, Sicily and Sardinia. The aims of this study were twofold. First, to provide data on the genetic diversity of pubescent oaks from an understudied area which currently exhibits one of the highest concentrations of pubescent oak species in Europe. Second, to verify if these groups of oaks are genetically distinct and if their identification is in accordance with the current taxonomic classification. Molecular analyses of leaf material of 480 trees from seventeen populations belonging to putatively different pubescent oak species (Quercus amplifolia, Q. congesta, Q. dalechampii, Q. ichnusae, Q. leptobalanos, Q. virgiliana) were performed. Twelve gene-based Expressed Sequence Tag-Simple Sequence Repeat markers were selected, and genetic diversity and differentiation were calculated. The results showed relatively high values of allelic richness, heterozygosity and number of private alleles for the populations investigated. A weak but positive correlation between geographical and genetic distance was detected. Genetic assignment (STRUCTURE) and principle coordinate analyses exhibited a weak separation into two genetic groups which, however, did not correspond to the taxonomic, chorological and ecological features of the populations investigated. Sardinian populations formed one group which was separated from the Calabrian and Sicilian populations. In light of the results obtained, the taxonomic classification for the pubescent white oaks currently reported in the major Italian floras and checklists for the study area was not confirmed by molecular analyses.
Highlights
The deciduous oak woods represent the most abundant forest vegetation type in southern Europe (Mucina et al 2016)
We hypothesize that the rugged morphology and wide altitudinal amplitude may have played a role in preserving the spatial contiguity between oak woods in the study area during the Quaternary climatic oscillations and in preserving high levels of gene flow
A genetic confirmation for a taxonomical classification providing up to seven pubescent oak species as occurring in the study area did not emerge from this study, despite reported by the most recent floras and checklists and by phytosociological papers as well
Summary
The deciduous oak woods represent the most abundant forest vegetation type in southern Europe (Mucina et al 2016). Even at the southernmost tip of Italy and Sicily the thermophilous deciduous oak forests cover a wider area than evergreen oak forests (Gianguzzi et al 2015) whereas the opposite is true for Sardinia where only 15% of the territory is potentially covered by deciduous oaks (Bacchetta et al 2009). Both taxonomic and phytosociological literature report that the thermophilous broad-leaved forests of southern Italy, Sicily and Sardinia are characterized by different pubescent oak species occurring in sympatry. The high concentration of putative pubescent white oak species suggests that southern Italy, Sicily and Sardinia acted
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