Why are there so few fish in the sea?

The most dramatic gradient in global biodiversity is between marine and terrestrial environments. Terrestrial environments contain approximately 75-85% of all estimated species, but occupy only 30 per cent of the Earth's surface (and only approx. 1-10% by volume), whereas marine environments occupy a larger area and volume, but have a smaller fraction of Earth's estimated diversity. Many hypotheses have been proposed to explain this disparity, but there have been few large-scale quantitative tests. Here, we analyse patterns of diversity in actinopterygian (ray-finned) fishes, the most species-rich clade of marine vertebrates, containing 96 per cent of fish species. Despite the much greater area and productivity of marine environments, actinopterygian richness is similar in freshwater and marine habitats (15 150 versus 14 740 species). Net diversification rates (speciation-extinction) are similar in predominantly freshwater and saltwater clades. Both habitats are dominated by two hyperdiverse but relatively recent clades (Ostariophysi and Percomorpha). Remarkably, trait reconstructions (for both living and fossil taxa) suggest that all extant marine actinopterygians were derived from a freshwater ancestor, indicating a role for ancient extinction in explaining low marine richness. Finally, by analysing an entirely aquatic group, we are able to better sort among potential hypotheses for explaining the paradoxically low diversity of marine environments.     

Biomass diversity and stability of food webs in aquatic ecosystems

The diversity–stability hypothesis in ecology asserts that biodiversity begets stability of ecological systems. This hypothesis has been supported by field studies on primary producers in grasslands, in which the interaction between species is mostly competition. As to ecosystems with multitrophic predatory interaction, however, no definite consensus has been arrived at for the relation between trophic diversity and ecosystem stability. The stability index suitable to ecosystems with predatory interaction is given by MacArthurs idea of stability and its formulation by Rutledge et al. More suitable indices of stability (relative conditional entropy) are proposed in this study for the comparison of different ecosystems, and the validity of the diversity–stability hypothesis for food webs (networks of predation) with many trophic compartments in natural aquatic ecosystems is examined. Results reveal that an increase in the biomass diversity of trophic compartments causes an increase in the whole systemic stability of food webs in aquatic ecosystems. Hence, evidence of the whole systemic validity of the diversity–stability hypothesis for natural aquatic ecosystems with ubiquitous multitrophic predatory interaction was obtained for the first time.     

湖北黄石典型水域超微型真核浮游生物多样性研究

为探讨湖北省黄石市典型水域中超微型真核浮游生物多样性, 采用18S rDNA 扩增片段限制性酶切技术, 结合优势类群测序及相关统计学分析, 对2015年夏季湖北黄石境内营养程度不同的典型水域(长江, 磁湖, 青山湖, 青港湖)中超微型真核浮游生物的群落组成及遗传多样性进行了研究。结果表明, 4个水域的超微型真核浮游生物多样性有明显差异, 多样性随水域营养化程度的增高而降低。优势克隆的测序结果显示, 优势类群藻类包括隐藻、绿藻、甲藻, 真菌包括隐真菌和壶菌, 此外还有纤毛虫及未分类的浮游生物, 隐藻在4个水域中都占优势。不同水域的优势类群差别较大。优势类群的种类随水域营养化程度的增加而减少。群落的多样性与总磷呈极显著的负相关。     

东海六个国家级海洋保护区鱼类多样性和连通性

全球气候变化和人类活动影响对沿海生态系统造成了巨大压力, 而建立海洋保护区网络被认为是应对这双重压力的重要手段。为了保护东海丰富的生物资源, 我国自20世纪末已建立了多个保护区, 但目前生物多样性以及连通性的研究不足以有效支撑东海生物多样性保护与可持续发展。为此, 本研究选取了东海城洲岛国家级海洋公园(城洲岛)、深沪湾海底古森林遗迹国家级自然保护区(深沪湾)、湄洲岛国家级海洋公园(湄洲岛)、平潭综合实验区海坛湾国家级海洋公园(平潭岛)、洞头国家级海洋公园(洞头岛)和玉环国家级海洋公园(玉环) 6个国家级海洋保护区, 在保护区内近岸海域采集不同季节的eDNA样品并测量水环境参数, 通过对鱼类群落组成分析预测保护区间的生物多样性及其潜在连通性。在采集到的71个样品中, 共获得了5,069,193条序列, 包括46,309个分子操作分类单元(molecular operational taxonomic units, MOTUs), 其中保护区内共享MOTUs的丰度占比基本都超过40%。虽然不同保护区间环境参数存在显著差异, 但是生物多样性指数和群落组成差异性检验显示不同保护区间鱼类组成不存在显著差异(P > 0.05), 仅存在季节差异。高占比的共享MOTUs以及无显著空间分化的群落组成可能意味着这些保护区间存在较强的连通性, 具备建立海洋保护区网络的潜力。对保护区生态网络结构的进一步分析表明, 不同保护区的生态网络存在差异, 洞头岛、玉环、深沪湾保护区的网络结构较为稳健, 而湄洲岛和平潭岛保护区则相反, 这表明不同保护区的保护效果存在一定差异, 这可能与保护区的面积和管理有关。本研究不仅为东海近岸群落连通性研究提供了参考, 同时也为东海保护区的管理和建设提供直接支撑。     

环境DNA技术在鱼类生态学中的应用研究进展

全球渔业衰退是21世纪人类面临的重要挑战之一。为了有效地遏制鱼类资源的衰退,精确的鱼类生态调查是其首要任务。传统的鱼类监测以渔获物采集与形态学鉴定为主,往往耗时耗力且效果不佳,已无法满足现阶段大尺度上的精确调查。环境DNA （eDNA）技术作为一种近年来新兴的鱼类生态调查方法,其与传统方法相比具有灵敏度高、经济高效、采样受限小且对生态系统无干扰的优势,目前其已被广泛地应用于鱼类物种监测、多样性调查、生物量评估以及繁殖活动监测等方面的研究。然而,eDNA技术在鱼类生态学研究的具体应用中暴露出的一些问题将会影响其监测结果的精确性,诸如操作流程的不规范、基因数据库的不完善以及eDNA在环境中生态学过程的不明确等。鉴于上述原因,首先对eDNA技术的发展历程、分析流程以及eDNA技术在鱼类生态学研究领域中的研究进展进行了综述,而后着重分析了eDNA技术的发展当前所面临的困难与挑战,并提出了相应的解决方案,最后对eDNA技术未来在鱼类生态学研究领域中的发展趋势做出了展望。通过本研究,以期能够为eDNA技术在鱼类生态学领域中的准确应用提供理论基础。     

基于环境DNA宏条形码技术的秦淮河生物多样性研究

秦淮河是南京的母亲河,其生物多样性受城市化进程影响面临严重威胁,而物种资源调研是生物多样性保护的基础。环境DNA宏条形码技术较形态学监测是一种简单高效、灵敏度高的新型监测技术。为探究秦淮河浮游生物、底栖动物及鱼类的生物多样性,于2019年7月,采用环境DNA宏条形码技术对其进行了探究,并分析了秦淮河上下游间的差异及环境因子对其群落结构的影响。结果表明:秦淮河共监测到浮游动物13属22种407个操作分类单元(Operational Taxonomic Units, OTUs),浮游植物85属60种4445个OTUs,底栖动物16属17种212个OTUs,鱼类53属44种1663个OTUs。其中浮游动物以游泳轮虫目(Ploima)和双甲目(Diplostraca)为主,共占浮游动物63.37%,浮游植物以隐藻门(Cryptomonas)和褐藻门(Ochrophyta)为主,共占浮游植物88.11%,底栖动物中节肢动物门(Arthropoda)占比最高,达91.67%,鱼类中鲤形目(Cypriniformes)占比最高,达69.99%。与秦淮河历史形态学监测数据相比,环境DNA宏条形码技术在...     

Climate impacts at multiple scales: evidence for differential population responses in juvenile Chinook salmon

1. We explored differential population responses to climate in 18 populations of threatened spring-summer Chinook salmon Onchorynchus tshawytscha in the Salmon River basin, Idaho. 2. Using data from a long-term mark-release-recapture study of juvenile survival, we found that fall stream flow is the best predictor of average survival across all populations. 3. To determine whether all populations responded similarly to climate, we used a cluster analysis to group populations that had similar annual fluctuations in survival. The populations grouped into four clusters, and different environmental factors were important for different clusters. 4. Survival in two of the clusters was negatively correlated with summer temperature, and survival in the other two clusters was positively correlated with minimum fall stream flow, which in turn depends on snow pack from the previous winter. 5. Using classification and regression tree analysis, we identified stream width and stream temperature as key habitat factors that shape the responses of individual populations to climate. 6. Climate change will likely have different impacts on different populations within this metapopulation, and recognizing this diversity is important for accurately assessing risks.     

环境DNA metabarcoding及其在生态学研究中的应用

环境DNA metabarcoding(eDNA metabarcoding)是指利用环境样本(如土壤、水、粪便等)中分离的DNA进行高通量的多个物种(或高级分类单元)鉴定的方法。近年来,该方法引起了学者的广泛关注,逐渐应用于生物多样性研究、水生生物监测、珍稀濒危物种和外来入侵物种检测等生态学领域。介绍环境DNA metabarcoding的含义和研究方法;重点介绍环境DNA metabarcoding在物种监测、生物多样性研究和食性分析等生态学领域中的应用;总结环境DNA metabarcoding应用于生态学研究领域面临的挑战并对该方法的发展进行展望。