Super-species in the calcareous plankton
Super-species in the calcareous plankton
复制标题
钙质浮游生物中的超级物种
DOI：
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发表时间：
2004
期刊：
影响因子：
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通讯作者：
H. Thierstein
中科院分区：
文献类型：
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作者：
C. Vargas;A. Sáez;L. Medlin;H. Thierstein
现代海洋中最成功的远洋原生动物群体进化出了汇聚的表型特征，包括细胞周围存在坚硬的骨骼。自侏罗纪以来，这些微骨骼-测试、球石、锥体、囊膜-积累了数公里的深海沉积物，这是最完整和最连续的化石记录，广泛用于重建地球系统动力学和微生物进化。在这些群体中使用传统的形态物种概念表明，生活在给定时间的相对较少的物种具有巨大的、往往是环绕全球的生物地理分布，并且通常在沉积物记录中持续数百万年，这与海洋水团中忙碌的生物生活节奏形成对比，导致了任何生态系统维持的最高的生物周转之一。在这里，我们回顾了所有关于球虫和有孔虫生物多样性的最新遗传数据。在这两个群体中，对各种基因的测序表明，形态上的物种实际上是兄弟物种的单系组合，根据分子钟计算，这些物种在数百万年前就出现了分歧。此外，形态实体内的兄弟种可系统地占据归因于传统形态种的总生态范围中有限的地理或时间上的异地细分。它们还表现出稳定和微妙的形态差异--尽管有数百万年的遗传隔离--这些差异以前被忽视或解释为生态表型变异。显然，与海洋浮游生物领域的生命有关的各种选择力量对远洋生物施加了强大的稳定选择，通过兄弟物种的起源和可能的灭绝来保持“最佳”表型。我们认为，这种进化模式是包括后生动物在内的大多数海洋浮游动物的特征，我们引入了“浮游超物种”的概念来描述这些受限的形态单系实体，其中包括适应不同生态位的几个兄弟物种。在现有的形态测量学和DNA数据集的框架下，讨论了两种不同的进化模型，它们在形态和遗传/生态分化之间的时空脱节中表现出不同的复杂程度。在分子系统发育学和微种子学之间设计实验方案将是测试我们的哪些模型反映现实世界的必要条件。这也将是揭示微化石在古生态学和地层学中应用的全部潜力的关键一步，并在适应和选择的层面上了解远洋生物多样性如何对过去海洋的气候变化作出反应，以及它可能如何对预计在不久的将来发生的严重变暖事件作出反应。
The most successful groups of pelagic protists in the modern Ocean have evolved convergent phenotypic traits, including the presence of hard skeletons enclosing the cell. These micro-skeletons – tests, coccoliths, frustules, theca – have accumulated kilometers of deep-sea sediments since the Jurassic, the most complete and continuous fossil record widely used for reconstructing Earth systems dynamics and microbial evolution. The use of the traditional morphological species concepts in those groups indicates that the relatively few species living at a given time have huge, often circum-global biogeographic distributions, and commonly last for many million years in the sediment record, which contrasts with the hectic biological pace of life occurring in the oceanic water masses, leading to one of the highest organismic turnover that any ecosystem sustains. Here we review all recent genetic data on coccolithophore and foraminifer biodiversity. In both groups, the sequencing of various genes shows that the morphological ‘species’ are in fact monophyletic assemblages of sibling species which diverged several million years ago according to molecular clock calculations. Furthermore the sibling species within a morphological entity may systematically occupy restricted geographic or temporal allopatric subdivisions of the total ecological range attributed to the traditional morphospecies. They display also stable and subtle – despite million years of genetic isolation – morphological differences that have been previously overlooked or interpreted as ecophenotypic variations. Obviously, various selective forces related to life in the marine planktic realm impose a strong stabilizing selection on pelagic organisms that maintains “optimal” phenotypes through the origination and possibly extinction of sibling species. We propose that this mode of evolution is characteristic of most marine planktic taxa, including metazoans, and we introduce a concept of ‘planktic super-species’ to describe these constrained morphological monophyletic entities that include several sibling species adapted to different ecological niches. Two different evolutionary models displaying different degrees of complexity in the spatio-temporal disconnection between morphological and genetic/ecologic differentiations are discussed in the frame of the existing morphometric and DNA data sets. The design of experimental protocols at the boundary between molecular phylogenetics and micropa-leontology will be a necessary condition to test which of our models reflect the real world. This will be also a crucial step to reveal the full potential of microfossil applications in paleoecology and stratigraphy, and to understand, at the level at which adaptation and selection operate, how pelagic biodiversity reacted to climatic changes in the past oceans and how it may react to the severe warming events projected in the near future.