Comparative systematics and phylogeography of Quercus Section Cerris in western Eurasia: inferences from plastid and nuclear DNA variation

PeerJ

article

Marco Cosimo Simeone¹  Simone Cardoni¹  Roberta Piredda²  Francesca Imperatori¹  Michael Avishai³  Guido W. Grimm⁴  Thomas Denk⁵ 

[1] Department of Agricultural and Forestry Science ,(DAFNE), Università degli Studi della Tuscia;Stazione Zoologica Anton Dohrn;Jerusalem Botanical Gardens, Hebrew University of Jerusalem;Orleans;Department of Palaeobiology

关键词: Section cerris;    Quercus;    Evolution;    Plastid DNA;    Phylogeography;    Western Eurasia;    Nuclear Ribosomal 5S-IGS;   

DOI  :  10.7717/peerj.5793

学科分类：社会科学、人文和艺术（综合）

来源: Inra

【 摘 要 】

Oaks (Quercus) comprise more than 400 species worldwide and centres of diversity for most sections lie in the Americas and East/Southeast Asia. The only exception is the Eurasian sect. Cerris that comprises about 15 species, most of which are confined to western Eurasia. This section has not been comprehensively studied using molecular tools. Here, we assess species diversity and provide a first comprehensive taxonomic and phylogeographic scheme of western Eurasian members of sect. Cerris using plastid (trnH-psbA) and nuclear (5S-IGS) DNA variation with a dense intra-specific and geographic sampling. Chloroplast haplotypes primarily reflected phylogeographic patterns originating from interspecific cytoplasmic gene flow within sect. Cerris and its sister section Ilex. We identified two widespread and ancestral haplotypes, and locally restricted derived variants. Signatures shared with Mediterranean species of sect. Ilex, but not with the East Asian Cerris oaks, suggest that the western Eurasian lineage came into contact with Ilex only after the first (early Oligocene) members of sect. Cerris in Northeast Asia had begun to radiate and move westwards. Nuclear 5S-IGS diversification patterns were more useful for establishing a molecular-taxonomic framework and to reveal hybridization and reticulation. Four main evolutionary lineages were identified. The first lineage is comprised of Q. libani, Q. trojana and Q. afares and appears to be closest to the root of sect. Cerris. These taxa are morphologically most similar to the East Asian species of Cerris, and to both Oligocene and Miocene fossils of East Asia and Miocene fossils of western Eurasia. The second lineage is mainly composed of the widespread Q. cerris and the narrow endemic species Q. castaneifolia, Q. look, and Q. euboica. The third lineage comprises three Near East species (Q. brantii, Q. ithaburensis and Q. macrolepis), well adapted to continental climates with cold winters. The forth lineage appears to be the most derived and comprises Q. suber and Q. crenata. Q. cerris and Q.  trojana displayed high levels of variation; Q. macrolepis and Q. euboica, previously treated as subspecies of Q. ithaburensis and Q. trojana, likely deserve independent species status. A trend towards inter-specific crosses was detected in several taxa; however, we found no clear evidence of a hybrid origin of Q. afares and Q. crenata, as currently assumed.

【 授权许可】

CC BY