Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA.
Proc Natl Acad Sci U S A. 2012 Nov 20;109(47):E3241-50. doi: 10.1073/pnas.1202690109. Epub 2012 Oct 22.
Deep-sea hydrothermal vents are populated by dense communities of animals that form symbiotic associations with chemolithoautotrophic bacteria. To date, our understanding of which factors govern the distribution of host/symbiont associations (or holobionts) in nature is limited, although host physiology often is invoked. In general, the role that symbionts play in habitat utilization by vent holobionts has not been thoroughly addressed. Here we present evidence for symbiont-influenced, regional-scale niche partitioning among symbiotic gastropods (genus Alviniconcha) in the Lau Basin. We extensively surveyed Alviniconcha holobionts from four vent fields using quantitative molecular approaches, coupled to characterization of high-temperature and diffuse vent-fluid composition using gastight samplers and in situ electrochemical analyses, respectively. Phylogenetic analyses exposed cryptic host and symbiont diversity, revealing three distinct host types and three different symbiont phylotypes (one ε-proteobacteria and two γ-proteobacteria) that formed specific associations with one another. Strikingly, we observed that holobionts with ε-proteobacterial symbionts were dominant at the northern fields, whereas holobionts with γ-proteobacterial symbionts were dominant in the southern fields. This pattern of distribution corresponds to differences in the vent geochemistry that result from deep subsurface geological and geothermal processes. We posit that the symbionts, likely through differences in chemolithoautotrophic metabolism, influence niche utilization among these holobionts. The data presented here represent evidence linking symbiont type to habitat partitioning among the chemosynthetic symbioses at hydrothermal vents and illustrate the coupling between subsurface geothermal processes and niche availability.
深海热液喷口是密集的动物群落的栖息地，这些动物与化能自养细菌形成共生关系。迄今为止，我们对于哪些因素控制着宿主/共生体（或全共生体）在自然界中的分布的理解是有限的，尽管通常会涉及到宿主生理学。一般来说，共生体在喷口全共生体利用栖息地方面所起的作用尚未得到彻底解决。在这里，我们提出了证据表明，在劳盆地中，共生腹足动物（Alviniconcha 属）存在受共生体影响的、区域性的小生境分区。我们使用定量分子方法，对来自四个喷口场的 Alviniconcha 全共生体进行了广泛调查，同时使用气密采样器和原位电化学分析分别对高温和弥散喷口流体成分进行了特征描述。系统发育分析揭示了隐藏的宿主和共生体多样性，发现了三种不同的宿主类型和三种不同的共生体基因型（一种 ε-变形菌和两种 γ-变形菌），它们彼此之间形成了特定的共生关系。引人注目的是，我们观察到，具有 ε-变形菌共生体的全共生体在北部场占优势，而具有 γ-变形菌共生体的全共生体在南部场占优势。这种分布模式与由于深部地下地质和地热过程而导致的喷口地球化学差异相对应。我们假设，共生体可能通过化能自养代谢的差异，影响这些全共生体之间的小生境利用。这里呈现的数据为共生体类型与热液喷口化学合成共生体之间的栖息地分区联系提供了证据，并说明了地下地热过程和小生境可用性之间的耦合。
