栎属麻栎亚组与冬青栎组的质体捕获历史研究

Plastid capture history of subsect. Campylolepides and section Ilex(Fagaceae: Quercus)

关键词:  栎属, 麻栎亚组, 土耳其栎组, 冬青栎组, 质体捕获, 质体基因组渐渗

Key words:  Quercus, subsect. Campylolepides, section Cerris, section Ilex, plastid capture, plastid genome introgression

摘要:

栎属(Quercus)麻栎亚组(subsect. Campylolepides)包括麻栎(Q. acutissima)、栓皮栎(Q. variabilis)及小叶栎(Q. chenii)3个物种,是栎属土耳其栎组(section Cerris)的东亚分支,前人已经对麻栎亚组或组内物种的物种形成和谱系地理做过深入研究,也发现了土耳其栎组(section Cerris)曾与冬青栎组(section Ilex)发生过古基因渐渗并导致质体捕获,但目前麻栎亚组与冬青栎组质体的具体进化历史仍不清楚。该研究对15个冬青栎组的样品进行了基因组浅层测序,并整合先前发表的麻栎亚组及其近缘类群共计325个重测序数据,其中麻栎亚组3物种19居群276个体,利用这些数据进行质体基因组组装和分析。结果表明:(1)麻栎亚组3个物种间存在共享单倍型,但整个麻栎亚组的质体单倍型基本构成一个单系分支,嵌套在华中至四川凉山州一带冬青栎组物种组成的分支中。(2)麻栎亚组物种中一个来自辽东半岛的孑遗麻栎单倍型与冬青栎组物种万山栎(Q. pseudosetulosa)聚为一个进化枝。(3)两次质体捕获事件均发生在中新世中期,在此之后麻栎亚组与冬青栎组未发生过质体捕获,推测麻栎亚组跟冬青栎组物种目前已经形成近乎完全的生殖隔离。该研究表明冬青栎组和麻栎亚组在质体基因组的演化历史中经历了古老的质体捕获事件,并最终逐步形成了相对独立的演化路径。

Abstract:

Quercus subsect. Campylolepides contains three species: Q. acutissima, Q. variabilis and Q. chenii, which is the East Asian clade of Quercus section Cerris. Species formation and phylogeography of whole subsection or species within the subsection have been studied in detail. It has been also found that section Cerris had an ancient gene introgression with section Ilex, which led to the plastid capture. However, the specific evolutionary history of plastids in subsect. Campylolepides and section Ilex remains unclear. Our study performed low-coverage whole genome sequencing on 15 samples from section Ilex and integrated previously published data from subsect. Campylolepides and its relatives, resulting in a total of 325 resequencing data, of which 276 individuals were from three subsect. Campylolepides species and 19 populations. We assembled 325 plastids to perform phylogeographic analysis. The results were as follows:(1)There were shared haplotypes among three species of subsect. Campylolepides, but the plastid haplotypes of the entire subsect. Campylolepides form a monophyletic branch nested within section Ilex species which are distributed from central China to Liangshan, Sichuan.(2)A relictual haplotype of subsect. Campylolepides from the Liaodong Peninsula clustered with Q. pseudosetulosa, a specie of the section Ilex.(3)Both plastid capture events occurred in the middle Miocene, after which no plastid capture occurred between subsect. Campylolepides and section Ilex. It is hypothesized that subsect. Campylolepides and section Ilex have formed almost complete reproductive isolation. The study demonstrates that section Ilex and subsect. Campylolepides have undergone ancient plastid capture events in their evolution history, ultimately lead to the gradual formation of relatively independent evolutionary paths.