Genome size variation and polyploidy in the geographical range of Juniperus sabina L. (Cupressaceae)

ABSTRACT

Polyploidy and natural hybridization are considered as two major evolutionary processes involved in plant speciation and diversification. In conifers, natural hybridization has been noticed to be more frequent than polyploidy. Nevertheless, a few cases of polyploidy have been reported in the genus Juniperus. In this genus, a new variety Juniperus sabina var. balkanensis has been postulated to have arisen from an ancient hybridization between the tetraploid species Juniperus thurifera and the diploid species Juniperus sabina var. sabina. The genome size variation and the ploidy level of two J. sabina taxa were estimated by flow cytometry in a panel of 29 populations. All 13 populations of J. sabina var. sabina were diploid, with genome sizes ranging from 22.09 to 25.03 pg/2C, while the 16 populations of J. sabina var. balkanensis were tetraploid, with genome sizes ranging from 41.99 pg to 51.33 pg/2C. These findings open new venues towards the discovering of the polyploidization pathway of J. sabina var. balkanensis and to understand historical and ecological factors that explain its current geographical distribution.

KEYWORDS:

• Cytogeography
• genome size
• interspecific hybridization
• Juniperus sabina var. balkanensis
• Juniperus sabina var. sabina
• monoploid genome size
• polyploidy

Acknowledgments

This study was supported with funds provided by National Council for Scientific Research grant number CNRS-FS90 – Lebanon, the Saint Joseph University Research Counsel (CR-USJ) FS-111 and Baylor University, project 0324512 to RPA.

Also, authors would like to thank colleagues who provided samples of Juniperus and Dr Sophie Nadot for English revision of the paper.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Baylor University, project 0324512 to RPA [project 0324512];Saint Joseph University Research Council (CR-USJ) [FS-111];National Council for Scientific Research- Lebanon [CNRS-FS90].

Notes on contributors

Perla Farhat

Perla Farhat is a PhD student at Saint Joseph University (Lebanon) and University Paris Sud (France). Her research field is polyploidy and hybridization in conifers, and more broadly plant genome evolution. Contribution: She conceived and designed the study, performed most of the experiments, and wrote the manuscript.

Sonja Siljak-Yakovlev

Sonja Siljak-Yakovlev is a Research Director at CNRS (France). She is an expert in plant cytogenetics and genome evolution and plant systematics. Contribution: She conceived and designed the study, collected some plant material, performed experiments, contributed to the manuscript writing and approved the final version of manuscript.

Robert P. Adams

Robert P. Adams is a Professor at Baylor University (USA). He is an expert in evolutionary and systematic studies of Juniperus. Contribution: He provided most of the plant material, and contributed to the writing.

Magda Bou Dagher Kharrat

Magda Bou Dagher Kharrat is a Professor at Saint Joseph University (Lebanon). She is specialized in plant conservation biology, with expertise in cytogenetics. Contribution: She insured the funding of this study, co-supervised the study and contributed to the writing.

Thierry Robert

Thierry Robert is an Associate Professor at Sorbonne University (France). He is a plant population geneticist. Contribution: He supervised the study and coordinated the writing.