Department of Marine Science, University of Otago, New Zealand.
Department of Anatomy, School of Biomedical Sciences, University of Otago, New Zealand.
Ann Bot. 2024 Mar 8;133(1):169-182. doi: 10.1093/aob/mcad151.
Contrasting patterns of host and microbiome biogeography can provide insight into the drivers of microbial community assembly. Distance-decay relationships are a classic biogeographical pattern shaped by interactions between selective and non-selective processes. Joint biogeography of microbiomes and their hosts is of increasing interest owing to the potential for microbiome-facilitated adaptation.
In this study, we examine the coupled biogeography of the model macroalga Durvillaea and its microbiome using a combination of genotyping by sequencing (host) and 16S rRNA amplicon sequencing (microbiome). Alongside these approaches, we use environmental data to characterize the relationship between the microbiome, the host, and the environment.
We show that although the host and microbiome exhibit shared biogeographical structure, these arise from different processes, with host biogeography showing classic signs of geographical distance decay, but with the microbiome showing environmental distance decay. Examination of microbial subcommunities, defined by abundance, revealed that the abundance of microbes is linked to environmental selection. As microbes become less common, the dominant ecological processes shift away from selective processes and towards neutral processes. Contrary to expectations, we found that ecological drift does not promote structuring of the microbiome.
Our results suggest that although host macroalgae exhibit a relatively 'typical' biogeographical pattern of declining similarity with increasing geographical distance, the microbiome is more variable and is shaped primarily by environmental conditions. Our findings suggest that the Baas Becking hypothesis of 'everything is everywhere, the environment selects' might be a useful hypothesis to understand the biogeography of macroalgal microbiomes. As environmental conditions change in response to anthropogenic influences, the processes structuring the microbiome of macroalgae might shift, whereas those governing the host biogeography are less likely to change. As a result, increasingly decoupled host-microbe biogeography might be observed in response to such human influences.
宿主和微生物组生物地理学的对比模式可以深入了解微生物群落组装的驱动因素。距离衰减关系是一种由选择性和非选择性过程相互作用形成的经典生物地理模式。由于微生物组促进适应的潜力，微生物组及其宿主的联合生物地理学越来越受到关注。
在这项研究中，我们使用测序（宿主）和 16S rRNA 扩增子测序（微生物组）的组合来检查模型大型海藻 Durvillaea 及其微生物组的耦合生物地理学。除了这些方法之外，我们还使用环境数据来描述微生物组、宿主和环境之间的关系。
我们表明，尽管宿主和微生物组表现出共同的生物地理结构，但这些结构来自不同的过程，宿主生物地理学表现出经典的地理距离衰减迹象，但微生物组表现出环境距离衰减。通过对丰度定义的微生物亚群落的检查，发现微生物的丰度与环境选择有关。随着微生物变得不那么常见，主导的生态过程从选择性过程转向中性过程。与预期相反，我们发现生态漂移并没有促进微生物组的结构形成。
我们的结果表明，尽管宿主大型藻类表现出相对“典型”的生物地理模式，即随着地理距离的增加相似性逐渐降低，但微生物组更加多样化，主要由环境条件塑造。我们的研究结果表明，巴斯贝克的“一切都在任何地方，环境选择”假说可能是理解大型藻类微生物组生物地理学的有用假说。随着环境条件因人为影响而发生变化，塑造大型藻类微生物组的过程可能会发生变化，而那些控制宿主生物地理学的过程则不太可能发生变化。因此，可能会观察到越来越不相关的宿主-微生物生物地理学，以应对此类人为影响。
