Bridging the Rubicon: Phylogenetic analysis reveals repeated colonizations of marine and fresh waters by thalassiosiroid diatoms
Bridging the Rubicon: Phylogenetic analysis reveals repeated colonizations of marine and fresh waters by thalassiosiroid diatoms
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DOI：
10.1016/j.ympev.2007.03.024
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发表时间：
2007-10-01
影响因子：
4.1
通讯作者：
Theriot, Edward C.
中科院分区：
文献类型：
--
作者：
Alverson, Andrew J.;Jansen, Robert K.;Theriot, Edward C.
盐度对包括硅藻在内的许多生物的分布构成了重大障碍。硅藻的祖先是海洋生物，它们独立定居于淡水沃茨的次数以及促进这些转变的生理适应仍然是硅藻进化中的突出问题。硅藻在淡水沃茨的定殖被比作“破釜沉舟”，这意味着成功的定殖事件是罕见的、不可逆转的，并导致物种的大量多样化。为了验证这些假设，我们重建了海链藻目，在海洋和淡水沃茨具有高度多样性的硅藻谱系的进化。我们收集了类似的5.3 kb的DNA序列数据从核（SSU和部分LSU IDNA）和叶绿体基因组（psbC和rbcL）和重建的遗传学使用简约和贝叶斯方法。替代拓扑结构测试强烈拒绝所有以前的殖民假设，包括单系的主要淡水Stephanodiscaceae。结果表明，至少有三个独立的殖民地的淡水沃茨，而以前的帐户的淡水到海洋的过渡已被打折，这些结果提供了令人信服的证据，多达三个独立的重新殖民的海洋栖息地，其中两个导致物种形成事件。这项研究增加了宝贵的系统发育背景以前的辩论的性质，硅藻的盐度屏障，并提供了令人信服的证据表明，至少对于海链藻，盐度屏障可能不像以前认为的那么可怕。(c)2007年爱思唯尔公司All rights reserved.
Salinity imposes a significant barrier to the distribution of many organisms, including diatoms. Diatoms are ancestrally marine, and the number of times they have independently colonized fresh waters and the physiological adaptations that facilitated these transitions remain outstanding questions in diatom evolution. The colonization of fresh waters by diatoms has been compared to "crossing the Rubicon," implying that successful colonization events are rare, irreversible, and lead to substantial species diversification. To test these hypotheses, we reconstructed the phylogeny of Thalassiosirales, a diatom lineage with high diversity in both marine and fresh waters. We collected similar to 5.3 kb of DNA sequence data from the nuclear (SSU and partial LSU IDNA) and chloroplast genomes (psbC and rbcL) and reconstructed the phylogeny using parsimony and Bayesian methods. Alternative topology tests strongly reject all previous colonization hypotheses, including monophyly of the predominantly freshwater Stephanodiscaceae. Results showed at least three independent colonizations of fresh waters, and whereas previous accounts of freshwater-to-marine transitions have been discounted, these results provide compelling evidence for as many as three independent re-colonizations of the marine habitat, two of which led to speciation events. This study adds valuable phylogenetic context to previous debate about the nature of the salinity barrier in diatoms and provides compelling evidence that, at least for Thalassiosirales, the salinity barrier might be less formidable than previously thought. (c) 2007 Elsevier Inc. All rights reserved.