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| 鼠李科雀梅藤属的分子系统学和生物地理学研究 | |
| 其他题名 | Molecular phylogenetics and biogeography of Sageretia (Rhamnaceae) |
| 阳亿 | |
| 出版年 | 2017 |
| 学位类型 | 硕士 |
| 导师 | 孙航 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 摘要雀梅藤属（Sageretia Brongn.）隶属于鼠李科鼠李族，在地理上间断分布于美国南部至中南美洲、非洲东北部至亚洲南部至东部地区。全世界现存该属植物共约35种，其中，除有3–4种分布于新世界以及1种分布于非洲东北部以外，其余的全都分布于亚洲南部至东南部地区。本研究通过运用分子系统学和生物地理学研究方法，重建了该属的系统发育关系，估算了该属的起源分化时间，并结合气候和地质历史事件对该属新旧世界间断分布格局的成因做出了详细的探讨。1. 雀梅藤属的分子系统学研究本研究通过选取两个核基因片段（ITS、ETS）和三个叶绿体片段（psbA-trnH、petA-psbJ以及trnL-trnF）并运用最大简约法和贝叶斯推导法，在整个鼠李族的背景下对雀梅藤属进行了系统发育重建（以Maesopsideae和Ventilagineae为外类群）。基于核基因及叶绿体基因序列联合分析的分子系统学研究结果表明：(I) 雀梅藤属与由鼠李属和Frangula所构成的分支具有最近亲缘关系，但该结果未获得较强的支持；(II) 雀梅藤属为一很好的单系；(III) 该属属下可以分为四个大支，即主要分布于热带亚洲地区基部类群Clade 1，分布于热带和亚热带美洲地区的Clade 2，主要分布于非洲东北部和亚洲干旱环境地区的Clade 3和分布于较为湿润的中国亚热带东亚季风气候区的Clade 4，其中，Clade 3下的类群多具有适应干旱环境的相对小型的硬质叶片，而Clade 4下的类群则多具有相对大型的叶片，且质地较薄，表现出适应湿润环境的特点；(IV) 基于系统发育重建结果并结合形态学证据，我们提出雀梅藤属一新种，并将其命名为Sageretia liuzhouensis Y. Yang & H. Sun sp. nov.。2. 雀梅藤属的生物地理学研究基于上述五个基因片段（ITS、ETS、psbA-trnH、petA-psbJ以及trnL-trnF）序列联合分析的BEAST时间推算结果显示，Clade 1与该属其它分支、Clade 2与其姐妹群，以及Clade 3与Clade 4 的分化时间分别为15.28 Ma、9.28 Ma和5.47 Ma。结合祖先分布区重建结果和气候和地质历史事件，我们认为：雀梅藤属很可能于早古新世在古热带亚洲地区起源；中中新世时，基部分支Clade 1与该属其他类群出现分化并适应热带亚洲的森林环境；Clade 1姐妹群的祖先类群通过白令陆桥传播至北美并越过巴拿马地峡而扩散至南美，由于晚中新世的气候变冷以及白令陆桥发生断裂，致使该类群与亚洲类群发生隔离分化并于新世界泛热带区域内分化形成Clade 2，由此产生了雀梅藤属新旧世界泛热带间断分布的分布格局；旧世界内部，亚洲内陆干旱和东亚夏季季风的加强很可能促使Clade 3与Clade 4对其各自分布区环境的适应分化，并且旱生类群Clade 4沿亚洲西南部和阿拉伯半岛自亚洲干旱区向西传播而至非洲东北部地区。 |
| 英文摘要 | AbstractSageretia Brongniart is a genus of Rhamnaceae with a disjunct distribution between a region from southern United States to Central and South America and another from northeastern Africa to southeastern Asia. This genus contains about 35 species, with one distributed in northeastern Africa, three or four in tropical and subtropical America and the others in southern to eastern Asia. In this study we conducted molecular phylogenetic and biogeographical analysis not only to reconstruct its phylogeny relationship and to calculate divergence time but also to speculate the cause of the disjunct distribution in this genus with taking the geographical and climatic events in history into account. 1. Molecular phylogeny of SageretiaIn this study, two nuclear loci (ITS and ETS) and three plastid ones (psbA-trnH、petA-psbJ and trnL-trnF) were sequenced for phylogeny reconstruction. Phylogeny trees were constructed using Bayesian inference (BI) and maximum parsimony (MP) and selecting Maesopsideae and Ventilagineae as outgroups. The result from analysis combined all loci data suggested that: (I) Sageretia is closest with the clade formed by Rhamnus and Frangula in phylogeny but with weakly supported; (II) Sageretia is a monophyletic taxa; (III) this genus could be divided into four main clades, with Clade 1 (basal taxa) mainly distributed in tropical Asia, Clade 2 in tropical and subtropical America, Clade 3 mainly in arid areas of Asia and northeastern Africa and Clade 4 mainly in humid region of subtropical China where with the East Asia monsoon climate, thereinto, mainly taxa in Clade 3 have smaller and stiffer leaves which could help them to adapt to arid habitats while almost all species in Clade 4 owe larger and thinner ones that reflect an adaption to moist environments; (IV) we state a new species of Sagereia, namely S. liuzhouensis Y. Yang & H. Sun, based on the phylogenetic and morphological evidence.2. Biogeographical analysis of SageretiaThe result of BEAST analysis based on all five loci suggested that divergence age between Clade 1 and other clades is 15.28 Ma, Clade 2 and its sister group (Clade 3 + Clade 4) is 9.28 Ma and Clade 3 and Clade 4 is 5.47 Ma. Combined with geographical and climatic events in history and the result of ancestral area reconstructions, it suggested that: this genus may originate in palaeo-tropical Asia in early Paleocene; a divergence occured between Clade 1 and other clades, and the former showed an adaption to the environment of tropical forest in middle Miocene; the ancestors of Clade 2 dispersed to North America via the Bering land-bridge and then to south America with getting across the Isthmus of Panama, and a subsequent divergence occurred between Clade 2 and its Asian relatives as a consequence of impediments caused by the global cooling in late Miocene and the subsequent break of Bering land-bridge, these cause the formation of Sageretia’s current disjunct distribution between Old and New World in final; in the Old Word, the divergence between Clade 3 and Clade 4, in connection with developments of Asian drying in Miocene and strengthening of summer monsoon in East Asia about 8 Ma ago, may reflect the adaptions to different climates and environments, and Clade 4 may spread from Asia to northeastern Africa via southwestern Aisa and Arabia. |
| 中文关键词 | 鼠李科 ; 雀梅藤属 ; 白令海峡 ; 间断分布 ; 季风气候 |
| 英文关键词 | Rhamnaceae Sageretia Bering land-bridge disjunct distribution monsoon climate |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 植物学 |
| 来源机构 | 中国科学院昆明植物研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287892 |
| 推荐引用方式 GB/T 7714 | 阳亿. 鼠李科雀梅藤属的分子系统学和生物地理学研究[D]. 中国科学院大学,2017. |
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