澜沧江硅藻的地理分布模式与关键驱动因素

硅藻作为重要的初级生产者,在水域生态系统中发挥重要作用,然而目前对于大型河流中硅藻的地理分布特征和驱动因素知之甚少.本文以我国西南地区典型大河澜沧江干流1200 km河段为研究区域,基于真核微生物高通量测序数据集,探究浮游硅藻和底栖硅藻在不同河段的分布特征和关键驱动因子.结果表明,澜沧江浮游硅藻和底栖硅藻的物种多样性在上游自然河段较高,两类硅藻的群落结构在不同河段间存在显著差异,建坝对两类硅藻的优势属相对丰度均产生显著影响.方差分解分析结果表明,扩散限制是浮游硅藻和底栖硅藻地理分布的主导驱动因子,解释率分别为16.7%和29.8%.共现网络分析结果表明,相比底栖硅藻,浮游硅藻的种间竞争关系和网络连通性较强;梯级库区段两类硅藻的网络连通性均高于上游自然河段.本研究补充了大型河流硅藻地理生态分布的认知不足,同时揭示了河流硅藻群落对水电开发的响应.

Biogeographic Distribution Patterns of Diatoms in Lancang River and Their Key Drivers

As an important primary producer, diatoms play a key role in aquatic ecosystems. However, little is known about the geographical distribution characteristics and driving factors of diatoms in large rivers. In this study, based on a high-throughput sequencing dataset of microeukaryotes, we analyzed the diversities and community compositions of planktonic and sedimentary diatoms in the 1200 km mainstream of Lancang River, a typical large river in southwestern China. The results showed that the diversities of planktonic and sedimentary diatoms in Lancang River were higher in the upstream natural section, and the community compositions of both groups were significantly different among different river sections. Dam construction had a significant effect on the dominant genera. Variance partitioning analysis showed that dispersal limitation was a major driving factor for the distribution pattern of planktonic and sedimentary diatoms, with explanation proportions of 16.7% and 29.8%. Co-occurrence network analyses showed that the interspecific competition relationship and network connectivity of the planktonic diatom network were stronger than the sedimentary ones. The network connectivity of planktonic and sedimentary diatoms in the cascade reservoir section was higher than that of the upstream natural section. This study will help to better understand the biogeographical distribution of diatoms in large rivers and provide useful information for ecological responses of diatoms to dam construction in rivers.