入侵种南美蟛蜞菊与本土种蟛蜞菊杂种区的适应性渐渗研究

Being the most common consequences of natural hybridization, introgression was the stimulus of rapid adaptive evolution for many invasive species. However, not all the introgressions were adaptive, one pending issue for introgressive hybridizations, was what proportions of the gene flow mediated by introgressive hybridization between species were adaptive. In this study, we investigated the hybrid zones between an in-vasive plant Sphagneticola trilobata and its native congener S. calendulacea. Using genome scanning of SNPs with RAD-seqs among the introgressors and its parents, we parsed the patterns of the introgressed loci using both heterogeneity test of allele fre-quencies and the genomic cline mode , and some outliers with potential adaptive sig-nificances were screened out and validated and annotated by RNA-seq under cold stress. At the same time, according to our preliminary experimental evidences for the occurrence of cold tolerant phenotypes alike the S. trilobata, some adaptive intro-gressors with ascertained loci of cold tolerances were transplanted in the field at the cold marginal areas, and trait performances with cold tolerance were compared, to-gether with evidences of fitness; both genetic and phenotype evidences will provide compelling evidences whether adaptive introgression of cold tolerance occurred. This project will broaden our understanding the evolutionary significances of introgressive hybridization, also provide accurate forewarning information of the invasion potential.

遗传渐渗（introgression）是自然杂交最常见形式，也是部分入侵种产生快速适应性进化的重要机制。然而，物种间的渐渗并非都是适应性的，渐渗杂交中一个关键问题是, 物种间渐渗介导的基因流多大程度上是适应性的？本项目以入侵种南美蟛蜞菊与本土种形成的杂种区（hybrid zone）为研究对象，通过高通量测序技术RAD-seqs扫描亲本物种及其渐渗居群基因组水平的SNPs，采用等位基因频率异质性检验和基因组渐变模型分析渐渗位点的分布样式，鉴定渐渗居群基因组上的离群位点(outlier loci)并通过人工模拟低温胁迫获得表达水平的证据；结合野外同质园实验,比较亲本与渐渗个体在居群水平上的低温适应性性状及适合度，检验热带分布入侵种南美蟛蜞菊与耐低温蟛蜞菊杂种区是否发生了低温适应性渐渗。本项目将深化我们对渐渗杂交进化适应性规律的理解，提供南美蟛蜞菊入侵潜能的预警信息。

遗传渐渗（introgression）是自然杂交最常见形式，也是部分入侵种产生快速适应性进化的重要机制。然而，物种间的渐渗并非都是适应性的，渐渗杂交中一个关键问题是, 物种间渐渗介导的基因流多大程度上是适应性的？本项目以入侵种南美蟛蜞菊与本土种形成的杂种区（hybrid zone）为研究对象，通过高通量测序技术RAD-seqs对来自佛山的杂种区扫描亲本物种及其渐渗居群基因组水平的SNPs，采用等位基因频率异质性检验和基因组渐变模型分析渐渗位点的分布样式，基于632个诊断性位点和2845个随机位点鉴定渐渗居群基因组上的63个离群位点(outlier loci)，其中2个位点Loc 653、Loc 1054分别与与CBF代谢通路上两个关键因子AT1G19670 (chlorophyllase 1)、 AT5G58620 (zinc finger (CCCH-type) family protein)同源;人工模拟低温胁迫，显示渐渗个体低温耐受性与本土种接近，但未显示出超亲性状，差异表达分析显示包括上述两个位点在内的众多位点在亲本间呈现显著差异，渐渗亲本与本土种的表达更为相似；我们的研究结果显示，南美蟛蜞菊在与本土种的渐渗杂交中，出现了对低温适应性性状的渐渗，在自然选择作用下，在向高纬度扩张过程中，这些渐渗个体具有适合度优势，具有入侵的潜能，因此有必要对北部边缘分布的杂种区进行动态监测，防止新的入侵种的产生。本研究还发现，入侵种与本土种杂交的另外一个后果是本土种的快速遗传湮灭，这是一个亟待关注的保护生物学问题。