Genetic Study Reveals Complex Evolutionary History of Iberian White Oaks Through Introgression and Hybridization
A new genomic study using RAD-sequencing characterized 38 Iberian white oak taxa and uncovered a complex evolutionary history shaped by hybridization and gene flow. The research proposes two new subsections of white oaks and validates the existence of hybrid swarms forming a regional 'syngameon' — a network of interbreeding species. The findings reposition the Iberian Peninsula as a major center of oak diversity and evolutionary complexity in Europe.
Researchers applied RAD-sequencing (RAD-seq) to 38 Iberian white oak taxa, including hybrid forms known as nothotaxa, to reconstruct the evolutionary history of the group. The study identified two new subsections: one grouping temperate and Atlantic-distributed species (Group A), and another encompassing submediterranean marcescent oaks (Group B). Within Group A, the analysis recovered Q. estremadurensis and a Northwestern Iberian lineage — including Q. broteroana and Q. orocantabrica — as southwestern relatives of the broadly distributed European pedunculate oaks (Q. robur sensu lato). Group B provided molecular validation for hybrid swarms, supporting the concept of an Iberian oak syngameon in which gene flow between species plays a central evolutionary role. The study also expands current understanding of the phylogeography of European Section Quercus more broadly. Overall, the work establishes the Iberian Peninsula not merely as a glacial refugium but as an active generator and reservoir of oak diversity.
What's missing
RAD-seq captures only a fraction of the genome, and the authors do not discuss whether whole-genome sequencing might alter conclusions about introgression boundaries. The directionality and timing of historical gene flow events are not fully resolved, and the study acknowledges hybrid swarms without quantifying the degree of reproductive isolation between taxa. Long-term ecological implications of the syngameon concept for conservation management of Iberian oaks are not addressed.
What different sources said
- bioRxivCenter
The Iberian white-oak syngameon as a legacy of introgression in southern Europe
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