Mohapatra Madhusmita, Manu Shivakumara, Dash Stiti Prangya, Rastogi Gurdeep
Wetland Research and Training Centre, Chilika Development Authority, Balugaon, 752030, Odisha, India.
CSIR-Centre for Cellular and Molecular Biology, Hyderabad, 500048, India.
Environ Sci Pollut Res Int. 2025 Jun;32(29):17528-17547. doi: 10.1007/s11356-025-36646-3. Epub 2025 Jul 2.
Benthic bacteria, in particular those existing in seagrass rhizosphere, play pivotal roles in supporting the growth and health of their hosts and also in nutrient cycling. Abundant (AT, relative abundance ≥ 0.05%) and rare (RT, relative abundance ≤ 0.001%) taxa reflect two distinct species pools in bacterial communities that differ in their structure and function and are assembled by different ecological processes. However, the mechanisms and factors controlling their spatial β-diversity patterns and ecological assembly are least understood in tropical seagrasses compared to their temperate counterparts. As rhizospheric effect vary between single and mixed plant communities, we examined AT and RT in both mono- and mixed species seagrass meadows and compared them with bulk (un-vegetated) sediments in a tropical coastal lagoon, Chilika (India). Results showed that the β-diversity (Bray-Curtis dissimilarity) of the AT and RT differed across seagrass meadows. RT exhibited a much stronger decay in community similarity with increasing spatial distance between samples than the AT. Spatial variation in RT was driven almost entirely by species turnover, whereas in AT both nestedness and turnover components played an important role. All AT were habitat generalists with broader niche breadth and environmental tolerances, while the majority of RT (66%) were specialists possessing narrower niche breadth and lower environmental tolerances. Stochastic processes (mostly dispersal limitation, 70.65-89.71%) contributed to the assembly of AT in both seagrass and bulk sediments, while deterministic factors (primarily variable selection, 45.78-60.78%) controlled the assembly of RT. Overall, this study highlighted the importance of examining AT and RT in bacterial communities for a broader understanding of the spatial patterns and underlying assembly mechanisms in tropical seagrass meadows.
底栖细菌，尤其是那些存在于海草根际的细菌，在支持宿主的生长和健康以及养分循环方面发挥着关键作用。丰富类群（AT，相对丰度≥0.05%）和稀有类群（RT，相对丰度≤0.001%）反映了细菌群落中两个不同的物种库，它们在结构和功能上存在差异，并且由不同的生态过程组装而成。然而，与温带海草相比，热带海草中控制其空间β多样性模式和生态组装的机制和因素了解得最少。由于单种和混合植物群落的根际效应不同，我们研究了单种和混合物种海草草甸中的丰富类群和稀有类群，并将它们与印度奇利卡热带沿海泻湖的大量（无植被）沉积物进行了比较。结果表明，不同海草草甸中丰富类群和稀有类群的β多样性（Bray-Curtis相异度）存在差异。稀有类群的群落相似性随样本间空间距离的增加而衰减的程度比丰富类群要强得多。稀有类群的空间变异几乎完全由物种更替驱动，而在丰富类群中，嵌套和更替成分都发挥了重要作用。所有丰富类群都是具有更广泛生态位宽度和环境耐受性的生境泛化种，而大多数稀有类群（66%）是具有较窄生态位宽度和较低环境耐受性的特化种。随机过程（主要是扩散限制，70.65 - 89.71%）促成了海草和大量沉积物中丰富类群的组装，而确定性因素（主要是可变选择，45.78 - 60.78%）控制了稀有类群的组装。总体而言，这项研究强调了在细菌群落中研究丰富类群和稀有类群对于更广泛地理解热带海草草甸的空间模式和潜在组装机制的重要性。
