Species diversity of freshwater hyphomycetes in some streams of Pakistan. Comparison of sampling techniques

Freshwater hyphomycete communities in four streams were sampled by filtration of water samples, trapping conidia in artificial foam, and examination of alder leaf pack baits and random sampling of naturally occurring submerged leaves. No two communities of freshwater hyphomycetes detected by different sampling techniques used singly in a stream showed 100% similarity. Based on relative frequency values, the same 10 top-ranking species in a stream were detected by artificial foam trap and on the baited leaves. These species differed in ranking, and the community in artificial foam was riche than on baited leaves. Of the various communities detected by different sampling techniques used singly or in combination, those detected by artificial foam trap or a combination of this technique with leaf baiting or with leaf baiting and randomly sampled leaves or filtration showed the highest similarity to the total community based on data generated using four sampling techniques simultaneously.This work was conducted under Grant No. PSF Project Environment 3 from the Pakistan Science Foundation.     

漓江上游鱼类物种组成及其多样性分析

2013年4月—2014年1月,分季度对漓江上游干流及其4条支流(小溶江、川江、陆洞河和黄柏江)进行了4次鱼类物种多样性调查研究,共采集淡水鱼类72种,隶属于4目15科51属。以鲤形目为主,分别占总物种数和总个体数的62.50%和79.78%;鲤科占优势,占总个体数的51.99%;研究区域内以宽鳍鱲Zacco platypus、方氏品唇鳅Pseudogastromyzon fangi、马口鱼Opsariichthys bidens为优势种,分别占总个体数的26.76%、11.92%、10.50%;多样性结果显示:夏季鱼类多样性(Margalef物种丰富度Dma,Shannon-Wiener多样性指数H'e,Pielou均匀度指数Je)高于春季和冬季,秋季最低;漓江上游干流多样性高于其他4条支流,黄柏江优势种最明显(Simpson优势度指数λ最高),多样性最低。     

Invasive river plants from Portuguese floodplains: What can species attributes tell us?

Biological traits of aquatic and riparian plants were compared among invasive and non-invasive groups of species from both native and exotic taxa in Portuguese fluvial systems. Twenty-six riparian and aquatic species were selected and their frequency of occurrence and foliar percentage cover was analysed at 401 sampling sites on the main catchments of Central and Southern Portugal. Canonical correspondence analysis and a hierarchical clustering were applied to the species traits data set. No typical invader profile emerged from the analyses. However, some specific attributes were clearly related to the alien and native plant invasiveness, such as vegetative reproduction, fragment viability and life span. The results of the present work could help with the early detection of invasive plant species in Portuguese fluvial corridors. Electronic Supplementary Material Electronic supplementary material is available for this article atand accessible for authorised users.     

How important are terrestrial organic carbon inputs for secondary production in freshwater ecosystems?

1. Many freshwater systems receive substantial inputs of terrestrial organic matter. Terrestrially derived dissolved organic carbon (t‐DOC) inputs can modify light availability, the spatial distribution of primary production, heat, and oxygen in aquatic systems, as well as inorganic nutrient bioavailability. It is also well‐established that some terrestrial inputs (such as invertebrates and fruits) provide high‐quality food resources for consumers in some systems.
2. In small to moderate‐sized streams, leaf litter inputs average approximately three times greater than the autochthonous production. Conversely, in oligo/mesotrophic lakes algal production is typically five times greater than the available flux of allochthonous basal resources.
3. Terrestrial particulate organic carbon (t‐POC) inputs to lakes and rivers are comprised of 80%–90% biochemically recalcitrant lignocellulose, which is highly resistant to enzymatic breakdown by animal consumers. Further, t‐POC and heterotrophic bacteria lack essential biochemical compounds that are critical for rapid growth and reproduction in aquatic invertebrates and fishes. Several studies have directly shown that these resources have very low food quality for herbivorous zooplankton and benthic invertebrates.
4. Much of the nitrogen assimilated by stream consumers is probably of algal origin, even in systems where there appears to be a significant terrestrial carbon contribution. Amino acid stable isotope analyses for large river food webs indicate that most upper trophic level essential amino acids are derived from algae. Similarly, profiles of essential fatty acids in consumers show a strong dependence on the algal food resources.
5. Primary production to respiration ratios are not a meaningful index to assess consumer allochthony because respiration represents an oxidised carbon flux that cannot be utilised by animal consumers. Rather, the relative importance of allochthonous subsidies for upper trophic level production should be addressed by considering the rates at which terrestrial and autochthonous resources are consumed and the growth efficiency supported by this food.
6. Ultimately, the biochemical composition of a particular basal resource, and not just its quantity or origin, determines how readily this material is incorporated into upper trophic level consumers. Because of its highly favourable biochemical composition and greater availability, we conclude that microalgal production supports most animal production in freshwater ecosystems.

     

A new genus and species for the first recorded cave-dwelling Cavernicola (Platyhelminthes) from South America

Species diversity of Brazilian cave fauna has been seriously underestimated. A karst area located in Felipe Guerra, northeastern Brazil, which is a hotspot of subterranean diversity in Brazil, has revealed more than 20 troglobitic species, most of them still undescribed. Based on recent samplings in this karst area, we document the occurrence of the suborder Cavernicola (Platyhelminthes) in South American hypogean environments for the first time and describe a new genus and species for this suborder. Hausera Leal-Zanchet & Souza, gen. n. has features concordant with those defined for the family Dimarcusidae. The new genus is characterized by two unique features, viz. an intestine extending dorsally to the brain and ovovitelline ducts located dorsally to the nerve cords, which is complemented by a combination of other characters. The type-specimens of Hauserahauseri Leal-Zanchet & Souza, sp. n. are typical stygobionts, unpigmented and eyeless, and they may constitute an oceanic relict as is the case of other stygobiotic invertebrates found in this karst area in northeastern Brazil.     

Are alien fish a reliable indicator of river health?

1. The ability of many introduced fish species to thrive in degraded aquatic habitats and their potential to impact on aquatic ecosystem structure and function suggest that introduced fish may represent both a symptom and a cause of decline in river health and the integrity of native aquatic communities. 2. The varying sensitivities of many commonly introduced fish species to degraded stream conditions, the mechanism and reason for their introduction and the differential susceptibility of local stream habitats to invasion because of the environmental and biological characteristics of the receiving water body, are all confounding factors that may obscure the interpretation of patterns of introduced fish species distribution and abundance and therefore their reliability as indicators of river health. 3. In the present study, we address the question of whether alien fish (i.e. those species introduced from other countries) are a reliable indicator of the health of streams and rivers in south‐eastern Queensland, Australia. We examine the relationships of alien fish species distributions and indices of abundance and biomass with the natural environmental features, the biotic characteristics of the local native fish assemblages and indicators of anthropogenic disturbance at a large number of sites subject to varying sources and intensities of human impact. 4. Alien fish species were found to be widespread and often abundant in south‐eastern Queensland rivers and streams, and the five species collected were considered to be relatively tolerant to river degradation, making them good candidate indicators of river health. Variation in alien species indices was unrelated to the size of the study sites, the sampling effort expended or natural environmental gradients. The biological resistance of the native fish fauna was not concluded to be an important factor mediating invasion success by alien species. Variation in alien fish indices was, however, strongly related to indicators of disturbance intensity describing local in‐stream habitat and riparian degradation, water quality and surrounding land use, particularly the amount of urban development in the catchment. 5. Potential confounding factors that may influence the likelihood of introduction and successful establishment of an alien species and the implications of these factors for river bioassessment are discussed. We conclude that the potentially strong impact that many alien fish species can have on the biological integrity of natural aquatic ecosystems, together with their potential to be used as an initial basis to find out other forms of human disturbance impacts, suggest that some alien species (particularly species from the family Poeciliidae) can represent a reliable ‘first cut’ indicator of river health.     

赣江鱼类物种更新名录

赣江是长江的主要支流之一, 淡水鱼类多样性极其丰富, 但是目前对于该河流的鱼类多样性还未有充分的了解。本研究于2016年9月至2017年8月对赣江鱼类进行了实地调查, 结合历史文献资料并参考最新的分类学成果, 更新了赣江淡水鱼类名录。结果表明, 赣江共有淡水鱼类180种, 隶属于12目31科93属。其中, 土著鱼类174种, 外来鱼类6种。赣江鱼类以鲤形目为主; 鲤科种类最多, 其次是鲿科。更新的物种名录中, 包含23个新记录土著种, 其中有5个未被描述的新种; 有36个历史资料记载的种类被剔除出物种名录; 25个物种发生了分类地位的变更。此外, 本次调查有28种鱼类未采集到, 说明这些鱼类的种群数量正在急剧下降, 而这些鱼类分别属于洄游性、流水性和产漂流性卵等独特生态类型, 说明赣江鱼类多样性受到了严重的人为干扰。本研究所给出的赣江鱼类的更新物种名录, 可为今后的赣江鱼类多样性保护提供理论基础。     

Species diversity of freshwater hyphomycetes in some streams of Pakistan. III. Autumnal colonization of freshwater hyphomycetes on bait leaves

Significantly more species of freshwater hyphomycetes colonized bait leaves of alder (16 species) and willow (14 species) during early submersion period (1 wk) than those of oak (8 species). Production of conidia was also higher on alder and willow leaves than on oak leaves. Higher amounts of dry mass were lost from the alder (28.6%) and willow leaves (29.4%) than from the oak leaves (18.7%). Rapid loss of dry mass was accompanied by rapid development of a fungal community. Fungal species took a longer time (6 wk) to reach their peak of occurrence on oak than on willow and alder leaves (3–4 wk).Flagellospora curvula dominated the assemblages of freshwater hyphomycetes on alder and willow leaves, andLunulospora curvula dominated the assemblage on oak leaves. The freshwater hyphomycete community showed higher values of species diversity (H value) on oak leaves than on alder and willow leaves.     

Distribution and Abundance of Zooplankton in an Alkaline Freshwater Marsh in Northumberland County,Pennsylvania

The zooplankton community of two ponds in an alkaline marsh in central Pennsylvania were studied. The ponds were found to be distinctly different from one another with regard to species but similar when only zooplankton types are considered. The ponds were quite similar with respect to a number of physico-chemical characteristics but differed significantly with respect to alkalinity, conductivity, habitat type, vegetation, depth, and predation pressure.     

甘肃省鱼类资源现状及DNA条形码在鱼类物种鉴定中的应用

为了摸清甘肃省土著鱼类资源与分布现状, 探索DNA条形码在鱼类辅助物种鉴定中的适用性, 2012年6-9月对甘肃境内黄河水系、嘉陵江水系和河西内陆河水系进行了较全面的鱼类调查。共采集鱼类标本3,087尾, 隶属于5目10科38属64种, 以鲤科种类最多, 为30种, 占总种数的46.88%。物种多样性分析表明, 在黄河水系的夏河和庄浪河多样性指数是所有调查点中最低的, 分别为1.38和1.09。嘉陵江水系各河段的多样性指数较高(H = 2.15-3.27), 其次为河西内陆河水系(H = 2.01-2.83)。在河西内陆河水系中, 疏勒河的均匀度指数最高, 为1.10, 黑河最低(0.68)。庄浪河的优势度指数最高, 为0.34, 而嘉陵江干流两当段的优势度指数在所有调查点中最低, 为0.04。利用DNA条形码分析了49种662尾标本的COI基因部分序列, 大部分种类在neighbor-joining系统树中形成各自的单系, 种内平均遗传距离0.88%, 种间平均遗传距离为9.99%, 在种内和种间COI序列遗传距离之间形成明显的条形码间隙, 斯氏高原鳅(Triplophysa stoliczkae)与达里湖高原鳅(T. dalaica), 甘肃高原鳅(T. robusta)与似鲇高原鳅(T. siluroides), 嘉陵裸裂尻鱼(Schizopygopsis kialingensis)与黄河裸裂尻鱼(S. pylzovi)之间的遗传距离低于2%, 甘肃高原鳅与似鲇高原鳅不能通过COI基因片段区分开, 其他两对物种可以采用核苷酸诊断法来进一步区分。斯氏高原鳅和拉氏鱼岁(Phoxinus lagowskii)种内遗传分歧较大, 揭示种内可能存在隐存种。结果表明, 对某些近缘种和不同地理种群差异较大的物种, 要将分子、形态和地理分布特点结合起来才能准确鉴定。     

南岭地区鱼类多样性及其地理分布

鱼类是河流生态系统的重要组成部分, 对维系河流生态系统稳定性发挥关键作用。鱼类多样性作为评价河流环境变化的重要指标, 可以直接反映该地区河流生态系统的健康状况。南岭地区河流众多, 淡水鱼类多样性十分丰富, 但目前尚缺乏对此地区鱼类物种多样性及其地理分布的系统研究。本文基于历史文献资料和相关书籍(截至2024年1月10日), 系统整理了南岭地区鱼类物种组成信息。结果表明, 南岭地区共有淡水鱼类261种, 隶属11目29科121属。其中, 土著鱼类248种, 外来鱼类13种。南岭地区鱼类以鲤形目鲤科和爬鳅科鱼类为主, 分别占南岭地区鱼类总物种数的56.7%和7.3%; 受威胁鱼类共19种, 占南岭地区鱼类总物种数的7.3%, 有11种列入《国家重点保护野生动物名录》(2021), 有28种属于“国家重点保护经济水生动物”。南岭地区鱼类多样性正面临严峻挑战, 主要由于河流污染、水利设施开发和过度捕捞等人类活动的影响, 导致该地区受威胁物种和入侵物种比例上升。建议今后加强治理河流污染、保护鱼类栖息地、科学开展增殖放流等。本文整理所得的南岭地区鱼类物种名录可作为今后南岭地区鱼类生物多样性保护的参考依据。     

澜沧江-湄公河中上游淡水鱼类多样性

澜沧江-湄公河是东南亚最大的河流, 也是世界上淡水生物多样性最高的三大河流之一。由于特殊的地理位置和国际河流属性, 澜沧江-湄公河淡水鱼类的多样性现状仍缺乏系统的认识。本文在近20年调查的基础上, 系统整理了澜沧江-湄公河中上游32个支流或亚流域的淡水鱼类物种名录, 在此基础上对其种类组成和分布进行了分析, 并利用分类学多样性指数对澜沧江-湄公河中上游流域的物种多样性进行了评估。结果表明, 澜沧江-湄公河中上游共记录了淡水鱼类745种, 分属于2纲17目63科229属, 其中鲤形目鱼类451种, 占物种数的60.5%。分类学多样性指数显示, 从源头到中游, 淡水鱼类在分类阶元上的分布越来越均匀, 亲缘关系越来越远, 分类多样性越来越高。聚类分析(cluster analysis, CA)和多维尺度分析(multi-dimensional scaling, MDS)表明, 当Jaccard相似性系数为8.69时, 澜沧江-湄公河中上游32个亚流域可以分为源区、上游和中游3组; 相似性分析(ANOSIM)结果显示, 各组之间淡水鱼类组成差异显著(R = 0.877, P = 0.001)。相似性百分比分析(similarity percentage analysis, SIMPER)结果表明, 导致3组差异性的鱼类主要是鲤形目和鲇形目鱼类, 且随着地势阶梯的升高出现了科级、属级类群的替代。近几十年来, 随着流域各国人口的增长和经济的快速发展, 澜沧江-湄公河鱼类多样性和渔业资源面临严重威胁, 未来需加强流域内国家间合作, 在流域尺度上制定科学保护计划。