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liping515110铜虫 (小有名气)
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[求助]
求高手帮忙 润色一下我的英语翻译
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上述从不同视角看不同来源共生绿藻的系统发生地位得到的结果好像有点自相矛盾，但如果我们能吃透问题的实质，那么这两个不同的结果实质上是统一的。Trebouxiophyceae纲的绿藻一开始应是全部为自由生活种类，这个类群的进化和演变肯定也遵循普遍的进化规律。但由于宿主（称潜在宿主最为合适）摄食、绿藻在潜在宿主体表长期外共生或绿藻与潜在宿主长期共栖等诸多特殊因素，最终导致了绿藻与宿主间的内共生关系。而内共生关系建立前绿藻和潜在宿主的密切关系是非常随机的，源于绿藻本身物种的多样性以及潜在宿主的多样性；而内共生关系一旦建立，共生绿藻和宿主间又是高度专一的，某个宿主中的共生绿藻自然转移到其他宿主的可能性为零。简言之，好比Trebouxiophyceae纲的绿藻进化路线图是一棵有根的大树，绿藻-宿主共生关系是在不同的末端树叶上发生的。也就是说，在一定意义上讲追寻绿藻-宿主共生体中的共生绿藻的起源本身就是不可能有结论的悖论、或者说是毫无意义的。本文的一些结果证实了上述假说，如即使为同一类型的宿主内共生的绿藻分类地位也大相径庭，包括中国绿水螅在内的5株来源不同的绿水螅中共生绿藻在基于18S rRNA基因序列重建的ML树（图3-2）、MP树（图3-3）和Bayesian树（图3-4）中均未聚为单系群，其中Bayesian树中5株来源不同的绿水螅中共生绿藻就有5个不同的来源。 基于18S rRNA基因序列重建的3个系统发生树从Trebouxiophyceae纲的大框架来看，为何不同来源的共生绿藻似乎有一共同起源？Trebouxiophyceae纲中共生绿藻支系和无共生绿藻支系的绿藻与潜在宿主建立内共生前的密切关系的几率应该是同等的，但最终与宿主建立共生关系的绿藻为何集中在Trebouxiophyceae纲中共生绿藻支系，最好的解释可能是共生绿藻支系的绿藻在形态或生理特性上有一定共性，而这些共性适合与宿主建立内共生关系，这还有待于对共生绿藻及共生绿藻支系中自由生活绿藻在形态及生理特性的深入研究才能作出结论。 值得注意的是，无论是基于基于18S rRNA基因序列重建的系统发生树（图3-2，图3-3，图3-4）、还是基于ITS基因序列重建的系统发生树（图3-5，图3-6，图3-7），均显示中国绿水螅共生绿藻与从美国明尼苏达州埃塔斯加湖采集的一种小球藻Meyerella planktonica有较近的亲缘关系，这对于目前把淡水纤毛虫、水螅和海绵共生绿藻都归类于小球藻属（genus Chlorella）的做法提出了挑战。中国绿水螅共生绿藻的确切定种和命名目前尚早，寄希望于对该绿藻的进一步研究。 The above-mentioned results of the phylogenetic position of symbiotic algae from different sources ,which we obtained from two different perspectives, appears to be a bit contradictory, but if we can thoroughly understand the essence of the problem, we will find that the two different results are essentially uniform.The algae of Class Trebouxiophyceae should be once free-living species , and the evolution of this group must also follow the general laws of evolution. However, so many factors such as endocytosis in potential host and long-term interactions(Ectosymbiosis and Commensalism) between green algae and potential hosts, that eventually led to a endosymbiotic relationship.Because of the species diversity and the diversity of potential host, the interactions between algae and host occured randomly before the establishment of symbiotic relationship .While, once the symbiotic relationship have been established ,the relationship will be obligate,which means that one symbiotic algae corresponding to one host can not live in another when it was transferred.In brief, if we view the evolutionary roadmap of algae within Class Trebouxiophyceae as a big rooted tree, the symbiotic relationships between algae and hosts occurs on different leaves.In other words, it is meaningless to trace origin of the symbiotic algae in algae/host symbiont.Some results confirm the above hypothesis, the taxonomic status of symbiotic algae within the same type of host are also very different，In the ML、MP and Bayesian trees based on 18S rRNA gene sequences, symbiotic algae in 5 strains of green hydra(including hydra sinensis ) from different sources, are all not monophyletic, and in the Bayesian tree , the 5 strains of green hydra from different sources have 5 different origins. In the three phylogenetic trees based on 18S rRNA gene sequences, from the perspective of Class Trebouxiophyceae broad framework, why the symbiotic algae from different sources seem to have a common origin？Before a symbiotic relationship between free-living algae and potential host was established, the probability of potential host establishing a close relationship with free-living algae from symbiotic algae group should be equal to that of potential host establishing a close relationship with free-living algae from free-living algae group. However, it is worth noting that there are symbiotic algae only in symbiotic algae group but not in free-living algae group, and the best explanation may be that green algae from symbiotic green algae group have some common morphological and physiological characteristics which are beneficial to establishing of symbiotic relationship between them with host, while green algae from free-living algae group have not，but to draw a conclusion ,we should make an in-depth study in the morphology and physiological characteristics of symbiotic algae and the free-living algae within the symbiotic green algae group. It is important to note that,whether the phylogenetic trees reconstructed on the base of 18S rRNA gene sequences or the trees based on ITS gene sequences, have all shown a close genetic relationspip between hydra sinensis and Meyerella planktonica,which were collected from lake Itasca,Minnesota,USA, and this is a challenge for placing the symbiotic algae from freshwater ciliates ,hydra and sponges in genus Chlorella.That is to say, it is too early to definite and name the species of the symbiotic algae of hydra sinesis. 求高手帮忙批改一下我的英语文章的翻译 谢谢！！！ |
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