Exploring mechanisms that affect coral cooperation: symbiont transmission mode, cell density and community composition
Exploring mechanisms that affect coral cooperation: symbiont transmission mode, cell density and community composition
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DOI：
10.7717/peerj.6047
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发表时间：
2018-12-03
期刊：
影响因子：
2.7
通讯作者：
Bay, Line K.
中科院分区：
文献类型：
--
作者：
Kenkel, Carly D.;Bay, Line K.
珊瑚共生是珊瑚礁生态系统的关键，但促进和维持宿主和共生体之间合作的机制尚未完全解决。我们使用了一种遗传控制的设计来研究垂直共生体传输的作用，这是一种共生体直接从父母那里继承的进化机制，预计可以增强合作和全共生体适应性。六种珊瑚，三个垂直发射机和他们最近的水平传输的亲戚，表现出环境收购的共生体，被分割，并进行了为期2周的热应力实验。共生体细胞密度，光合功能和光合固定碳的转运之间的共生体和主机进行量化，以评估生理性能和合作的变化。所有物种表现出类似的共生体细胞密度和净光合作用在响应温度升高，漂白的发病一致的下降。然而，基线合作，或易位的光合作用，在环境条件下，减少合作，以应对温度升高的物种之间的差异。虽然滨珊瑚lobata和Galaxea acrhelia没有表现出最高水平的基线合作，我们没有观察到普遍较高水平的合作垂直传播的物种。事后测序的共生藻ITS-2位点被用来调查共生体社区组成的差异的潜在作用。有趣的是，在开始漂白合作减少往往与珊瑚物种之间的共生体群落多样性增加。进化垂直传播的理论好处是基于这样一个基本假设，即宿主-共生体关系在遗传上变得一致，从而减少了共生体之间的竞争。两者合计，我们的研究结果表明，它可能不是垂直传播本身的影响主机共生体的合作，但共生体社区的遗传均匀性，虽然需要更多的工作来验证这一假设。
The coral symbiosis is the linchpin of the reef ecosystem, yet the mechanisms that promote and maintain cooperation between hosts and symbionts have not been fully resolved. We used a phylogenetically controlled design to investigate the role of vertical symbiont transmission, an evolutionary mechanism in which symbionts are inherited directly from parents, predicted to enhance cooperation and holobiont fitness. Six species of coral, three vertical transmitters and their closest horizontally transmitting relatives, which exhibit environmental acquisition of symbionts, were fragmented and subjected to a 2-week thermal stress experiment. Symbiont cell density, photosynthetic function and translocation of photosynthetically fixed carbon between symbionts and hosts were quantified to assess changes in physiological performance and cooperation. All species exhibited similar decreases in symbiont cell density and net photosynthesis in response to elevated temperature, consistent with the onset of bleaching. Yet baseline cooperation, or translocation of photosynthate, in ambient conditions and the reduction in cooperation in response to elevated temperature differed among species. Although Porites lobata and Galaxea acrhelia did exhibit the highest levels of baseline cooperation, we did not observe universally higher levels of cooperation in vertically transmitting species. Post hoc sequencing of the Symbiodinium ITS-2 locus was used to investigate the potential role of differences in symbiont community composition. Interestingly, reductions in cooperation at the onset of bleaching tended to be associated with increased symbiont community diversity among coral species. The theoretical benefits of evolving vertical transmission are based on the underlying assumption that the host-symbiont relationship becomes genetically uniform, thereby reducing competition among symbionts. Taken together, our results suggest that it may not be vertical transmission per se that influences host-symbiont cooperation, but genetic uniformity of the symbiont community, although additional work is needed to test this hypothesis.