Format: ORAL

Perla Farhat 1,2,3, Sonja Siljak-Yakovlev 2, Thierry Robert 2,5, and Magda Bou Dagher Kharrat 1,5*

1 Laboratoire Biodiversité et Génomique Fonctionnelle, Faculté des Sciences, Université Saint-Joseph, Campus Sciences et Technologies, Mar Roukos, Mkalles, BP: 1514 Riad el Solh, Beirut 1107 2050, Lebanon. 2 Ecologie Systématique Evolution, Univ. Paris-Sud, CNRS, AgroParisTech, Université Paris-Saclay, 91190, Gif-sur-Yvette, France. 3 Sorbonne Université, CNRS, Integrative Biology of Marine Models, Station Biologique de Roscoff (SBR), 29680 Roscoff, France 4 Biology Department, Sorbonne Université, Jussieu, 75005 Paris, France. 5 European Forest Institute, Mediterranean, Sant Pau Art Nouveau Site, St. Antoni M. Claret, 167, 08025 Barcelona, Spain.

Polyploidy has long been recognized as a significant driver in the evolution of Angiosperms. Although the study of this phenomenon is limited in Gymnosperms, recent research has revealed that Juniperus is the only genus within this group that exhibits a high frequency of polyploidy. Here we aimed to assess the potential origin of five polyploid Juniperus taxa, including the only hexaploid taxon (J. foetidissima), using AFLP markers. Additionally, we aimed to evaluate gene flow between two Juniperus taxa that were suggested to be involved in the origin of the tetraploid J. sabina var. balkanensis. We utilized four chloroplast and nrDNA markers, along with flow cytometry measurements for ploidy level determination on samples from three populations in France and Spain where these two taxa are present in sympatry. Bayesian analysis of admixture based on AFLP data suggested an allopolyploid origin for the hexaploid species J. foetidissima, involving J. thurifera and J. sabina lineages. The tetraploid cytotypes of J. seravschanica were shown to originate from an allopolyploidy event, while no clear evidence of hybridization in the origin of the tetraploid J. thurifera and J. chinensis was detected. Furthermore, flow cytometry measurements on samples from the three studied populations in France and Spain revealed the presence of three ploidy levels: diploid for J. sabina samples, tetraploid for J. thurifera, and a rare triploid level found in few individuals. Based on chloroplast and nuclear markers, the triploid individuals were identified as hybrids resulting from a cross between the diploid J. sabina and the tetraploid J. thurifera. These findings contribute to our understanding of the polyploidy origin of Juniperus taxa and highlight the potential role of allopolyploidy in the evolution of this coniferous genus.