A new species of freshwater snail Tchangmargarya (Gastropoda: Viviparidae) endemic to a vanished small lake in Yunnan,China

Habitat loss poses a grave threat to endemic species with narrow distributions. Some species become extinct even before scientific identification due to habitat destruction. Here, a probable example is reported based on some recent and subfossil shells from an almost disappeared wetland lake in Yunnan Province, China. A new ornamented freshwater snail species, Tchangmargarya ziyi n. sp., is recognised and described based on morphological comparison with the other Tchangmargarya species. The subfossil specimens of the new species show a great similarity to Tchangmargrya yangtsunghaiensis (Tchang & Tsi, 1949), indicating their potentially close relationship. The discovery of the new species demonstrates that the plateau lakes of Yunnan, even the small ones, have a high biodiversity and endemism. Furthermore, it enriches the knowledge of the distribution of Tchangmargarya and provides further evidence that the Liangwang Mountains are a significant biogeographic barrier to three endemic viviparid genera (Margarya, Anularya and Tchangmargarya) of Yunnan. Since the only known habitat of this species has been mostly landfilled due to the construction of a golf course and villas, this species possibly has already gone extinct. In order to implement conservation measures more efficiently, more comprehensive surveys should be conducted in all plateau lakes of Yunnan, including those that might seem insignificant.     

云南不同高原湖泊噬藻体psbA基因多样性

【目的】噬藻体(cyanophage)广泛存在于自然水体生态系统中,通过侵染蓝藻进而调控蓝藻种群及群落结构,具有重要生态功能和生态地位,在控制蓝藻水华方面有巨大开发潜力。本研究旨在探究云南高原湖泊噬藻体psbA基因多样性,分析其系统进化地位,为深入了解高原湖泊生态功能、开发利用噬藻体资源奠定理论基础。【方法】以云南高原主要湖泊滇池、抚仙湖和星云湖等为研究对象,以psbA基因作为分子靶标,对湖泊水体中噬藻体遗传多样性进行研究。【结果】从不同湖泊中共获得100条环境噬藻体psbA基因序列,系统发育分析表明,湖泊的噬藻体psbA基因序列与中国东湖、中国东北稻田、日本稻田等淡水中的环境噬藻体psbA基因亲缘关系较近,与海洋环境噬藻体psbA基因亲缘关系较远;抚仙湖中的噬藻体psbA基因多样性高于滇池、星云湖和异龙湖中的噬藻体psbA基因多样性;云南高原湖泊中存在新的噬藻体类群;各湖泊秋冬季节噬藻体psbA基因遗传多样性差异不明显。【结论】云南主要高原湖泊噬藻体psbA基因遗传多样性高,与淡水环境噬藻体psbA基因亲缘关系较近,且存在独特的噬藻体类群。     

Effects of eutrophication and temperature on Cyclotella rhomboideo‐elliptica Skuja,endemic diatom to China

An endemic diatom, Cyclotella rhomboideo‐elliptica Skuja, from the Yunnan Plateau, has been disappearing gradually from some lakes of the plateau. This study investigated the diatom's distribution in 30 lakes and documents long‐term population changes in the paleolimnological record of a deep lake, Lake Fuxian. Living cells of C. rhomboideo‐elliptica were found in five Yunnan Plateau lakes in 1957, but cells were restricted to Lake Fuxian in 2005. Its absolute abundance fluctuated from low to high to low. Our study suggests that nutrient concentrations correlate with C. rhomboideo‐elliptica's s abundance and survival. We infer that the disappearance of C. rhomboideo‐elliptica in some lakes may be due to increased nutrient concentrations and the species may be indicators of low nutrients. During the study, we also found that decreased in the diatoms average long axis length after the early 1990s. This morphological change was likely due to higher nutrient concentrations or to the increase in temperature, or a combination of the two.     

A grey future for Europe: Sciurus carolinensis is replacing native red squirrels in Italy

Introduced mammals can cause extinction of native species due to replacement competition, disease, predation or hybridization. We studied the colonization of Piedmont (NW-Italy) by American grey squirrel (Sciurus carolinensis) and its effect on the native red squirrel (Sciurus vulgaris). Presence/absence data (2 × 2 km²), of both species were (re)constructed using questionnaires, literature, existing databases, unpublished information, and direct monitoring with hair-tubes. In 1970 red squirrels were still widespread and greys were restricted to forests near the introduction site. By 1990, grey squirrels had increased their range to 220 km², which coincided with the disappearance of native squirrels from 33 squares inside this range. The invasive species continued its spread occupying an area of 2,016 km² in 2010; within this area red squirrels went extinct in 88 squares. Overall, from 1970 to 2010 red squirrel went extinct in 62 % of 2 × 2 km² (ca. 1,689 km²), and were replaced by grey squirrels. The spread of the alien species was slow in the first 20 years, but doubled in the successive two decades. Nevertheless spread was slower than in Ireland and England. Grey squirrel adapt to climate and habitats in both North and South Europe, causing extinction of the native red squirrel. A EU LIFE co-funded project with the aim to control the grey squirrel in North Italy and recent trade-restrictions and trade-ban are a first step in reducing the risk of grey squirrels invading other countries, but their effectiveness will have to be evaluated.     

Diatom community succession in the recent history of a eutrophic Yunnan Plateau lake, Lake Dianchi, in subtropical China

Fish introduction, eutrophication and disappearance of aquatic vegetation are important disturbances of aquatic ecosystems, especially in plateau lakes, which are generally considered to be very vulnerable. Fish were introduced to Lake Dianchi, a eutrophic plateau lake in southwest China, in the late 1950s and 1970s. After the introduction, invasive fish became the dominant species, and the total fish yield increased. Meanwhile, the trophic level of Lake Dianchi had a tendency to increase in the past decades because of the increases in human activities in the watershed area. In addition, the area of aquatic vegetation decreased from more than 90 to 1.8% of the lake area from the 1950s to 2000. This study investigated the effects of fish introduction, eutrophication and aquatic vegetation on the diatom community of Lake Dianchi by examining the changes of microfossil diatom assemblage and abundance. Results showed that the absolute abundance and diatom assemblages changed after fish were introduced. The endemic species, Cyclotella rohomboideo-elliptica, disappeared with the introduction of fish and increasing trophic levels after 1958. Fragilaria crotonensis entered into the lake with the introduction of fish and gradually thrived in the lake after 1958. Diatom species numbers also decreased gradually from 21 to 9 from the past to present. Epiphytic diatoms disappeared with the decrease of aquatic vegetation after 1985. Our study indicated that eutrophication was the most important process determining diatom abundance, and fish introduction was a secondary process determining diatom abundance, while aquatic vegetation had a more important role in structuring the diatom community in this eutrophic plateau lake.     

Growth and reproduction of the non‐native icefish Neosalanx taihuensis Chen, 1956 (Salangidae) in a plateau lake,southwestern China

Growth, reproduction and abundance traits of the invasive icefish Neosalanx taihuensis Chen, 1956 were investigated monthly from July 2009 to May 2011 in Lake Erhai on the Yunnan‐Guizhou Plateau, south‐western China, in order to explore the changes in life‐history traits after translocation. The results indicated that the icefish exhibited obvious plasticity in growth and reproduction traits. Growth of the fish in Lake Erhai was faster than that in native waters and in other translocated reservoirs. By fitting the von Bertalanffy growth model to the data, it was estimated that icefish obtain an asymptotic size of 96.12 mm, a K of 1.61, and a t₀ of ‐0.26; the calculated overall growth performance index φ′ was 4.17. The strategy of reproduction changed from multiple‐ to single‐spawning. The spawning period was from October to December with the absolute and relative fecundities of 1250 ± 169 eggs per ind and 2557 ± 245 eggs per g, respectively. Plasticity in icefish growth and reproduction in Lake Erhai greatly facilitated its population establishment, making it one of the most abundant fish species. The icefish invasion in the lake may be one of the reasons for the decrease or extinction of native fish species populations, and some measures for the control of this invasive fish are suggested.     

Three new species of Potamothrix (Oligochaeta, Naididae, Tubificinae) from Fuxian Lake, the deepest lake of Yunnan Province, Southwest China

Three new species of Potamothrix Vejdovsky & Mrázek, 1902 (Oligochaeta: Tubificinae), Potamothrix praeprostatussp. n., Potamothrix paramoldaviensissp. n. and Potamothrix parabedotisp. n., are reported from Fuxian Lake of Yunnan Province, Southwest China. Potamothrix praeprostatusdiffers from its allies by its prostate glands joining atria in its proximal to middle portion, and spermathecal chaetae. Potamothrix paramoldaviensis is distinguishable from its allies by having penial chaeta but no penes, and differs from Potamothrix moldaviensisby its homogenous atrium. Potamothrix parabedoti is distinctive in the position of its reproductive organs, and differs from Potamothrix bedoti by its homogenous atrium. Hitherto, 34 freshwater oligochaete species have been recorded in Yunnan Province, including nine endemic species from the plateau lakes.     

人为干扰对滇池湖滨区湿地高等植物种类组成的影响

引种高等植物构建半自然湿地生态系统,是修复遭受严重污染和破坏的湖泊湿地的重要方法之一.以2011-2012年滇池湖滨区26个样点128个样方的调查数据为基础,结合1960-1970年的研究资料,探讨了人为活动对滇池湖滨区高等植物种类的影响.结果表明: 2012年在滇池湖滨区共发现湿地高等植物88科299种,其中本土植物181种,外来植物118种(包括32种入侵物种);在42种水生植物中,13种为外来植物(包括2种入侵物种).与1960-1970年资料相比,新记录植物232种、已消失植物43种.其中,沉水植物、漂浮植物和浮叶植物分别减少了2种、2种和5种,挺水植物增加了8种.目前共有14个植物群落类型,新出现了以大薸、喜旱莲子草等外来植物为优势种的群落类型,而以海菜花、苦草等本土植物为优势种的植物群落已消失.在引种高等植物修复退化湖泊湿地时,应科学合理地选配植物物种,以免人工引发湿地退化.     

小鲤地理分化的研究

小鲤Ｃｙｐｒｉｎｕｓ ｍｉｃｒｉｓｔｉｕｓ分布于云南省的滇池、抚仙湖和星云湖,对历年馆藏和作者近年定期野外收集的２００尾标本和生态资料进行综合分析的结果表明：小鲤已分化为两个地理亚种,即滇池特有的小鲤指名亚种Ｃ．（Ｍ．）ｍｉｃｒｉｓｔｉｕｓ ｍｉｃｒｉｓｔｉｕｓ Ｒｅｇａｎ和分布于抚仙湖、星云湖的抚仙小鲤Ｃ．（Ｍ．）ｍｉｃｒｉｓｔｉｕｓ ｆｕｘｉａｎｅｎｓｉｓ Ｙａｎｇ ｅｔ ａｌ．,亚种间形态的     

云南滇池濒危特有种滇池金线鲃繁殖初报

滇池金线鲃(Sinocyclocheilus grahami)是滇池湖泊生态系统的指示物种和特有种。因水质污染和外来物种入侵等因素的影响,该鱼类自1986年起就从湖体中消失,仅有湖周围的少数龙潭中尚保存有少量滇池金线鲃。至2007年3月初,有两次繁殖试验取得了成功。先后试验了5尾雌鱼和6尾雄鱼,获得鱼卵约1600粒,并实施干法受精。约有1320粒受精,平均受精率为73%。孵化出鱼苗约480尾,平均孵化率为36%。经10天饲养,约有95%以上的鱼苗存活,体长达8-12mm。滇池金线鲃人工繁殖成功的意义有三点:能有效保护该物种免于灭绝;繁殖的鱼苗放归湖泊合适水域,将有助于恢复滇池的土著生物多样性;有助于推动当地水产养殖业从非土著鱼类养殖向土著鱼类养殖的方向转变。     

Drivers of extinction: the case of Azorean beetles

Oceanic islands host a disproportionately high fraction of endangered or recently extinct endemic species. We report on species extinctions among endemic Azorean beetles following 97% habitat loss since AD 1440. We infer extinctions from historical and contemporary records and examine the influence of three predictors: geographical range, habitat specialization and body size. Of 55 endemic beetle species investigated (out of 63), seven can be considered extinct. Single-island endemics (SIEs) were more prone to extinction than multi-island endemics. Within SIEs restricted to native habitat, larger species were more extinction-prone. We thus show a hierarchical path to extinction in Azorean beetles: species with small geographical range face extinction first, with the larger bodied ones being the most threatened. Our study provides a clear warning of the impact of habitat loss on island endemic biotas.     

Ecological evaluation of local extinction: the case of two genera of endemic Mexican fish, Zoogoneticus and Skiffia

The Goodeidae is a family of endemic fish from central Mexico. Populations of several species are declining in the wild and two have been reported extinct; Skiffia francesae and Zoogoneticus tequila. Both species were native to just one locality in the Ameca basin. It is difficult to infer the causes of extinction, since limnological data from Teuchitlán prior to the extinction events are not available, and there are no replicate populations. As an alternative approach, we explored the potential links between key environmental variables and events of local extinction of any species in the two genera (four Skiffia spp. and two Zoogoneticus spp.). In 14 localities known to harbour populations of fish of at least one of the six focal species, we conducted limnological surveys in the rainy and in the dry season, and quantified population densities of endemic and introduced fish. In addition, we quantified the concentration of agricultural pollutants in water and mud samples taken from every locality in the dry season. We found that all the focal species face some conservation threat, but we also discovered an extremely small population of the reputedly extinct Zoogoneticus tequila; in contrast, Skiffia francesae was not found. Eutrophication and habitat fragmentation appear to be the main threats to the focal species, with habitat fragmentation exponentially reducing population size and driving populations into refuges where they face stochastic extinction.     

The bounty of minor lakes: the role of small satellite water bodies in evolution and conservation of fishes in the Lake Victoria Region,East Africa

The Lake Victoria Region (LVR) encompasses the large lakes Victoria, Kyoga, Edward, George and Kivu, as well as scores of small satellite lakes within the parent catchments. Taken as a whole, the LVR originally harbored a unique fish fauna that included in excess of 600 endemic species of cichlid fishes. As a result of human influence, including a commercial fishery and the introduction of several exotic species, nearly 200 cichlid species and several endemic genera have become extinct from lakes Victoria and Kyoga. Recently, we have discovered that some of the apparently extinct taxa survive as extant representatives in the satellite lakes. Here, we summarize the findings of our ecological survey of the fish species of the satellite lakes. We also discuss the results of some preliminary genetic analyses, and highlight major genetic and ecological changes in the fish fauna that have taken place in the regional fishery. Minor lakes now play a crucial role in conserving the endangered species of the entire region, and also as living museums of East African ecological history. Our findings allude to the historical importance of minor satellite lakes as natural refugia for the fishes of the Lake Victoria Region, a region characterized by a history of geological and climatic instability.     

塔里木盆地鱼类入侵及区系演变趋势

鱼类入侵是塔里木盆地土著鱼类濒危的关键性影响因素之一,结合历史文献数据及近年调查数据,系统综述了塔里木盆地鱼类入侵现状,并就鱼类入侵引起的鱼类区系均一化问题进行了分析。结果显示,该地区记录鱼类63种,其中土著种19种,入侵种44种。尽管入侵鱼类提升了塔里木盆地鱼类群落属级及科级的多样性水平,但相应的G-F多样性指数却明显下降,表明该区鱼类群落从物种组成简单、分化明显的特点演变为物种成分复杂、分化贫乏的特点。入侵种中源于长江和额尔齐斯河分别有30种(68.2%)和7种(15.9%),源于美欧和亚洲其他区域的有7种(15.9%)。入侵鱼类的进入引起塔里木盆地与其相关区域鱼类区系相似性显著上升(P0.01),并导致该区鱼类区系从单一的中亚高原山区复合体演变为多区系混合体。进一步利用鱼类个体生态矩阵分析方法研究显示,外来种在塔里木盆地适应性广泛,能够占据水域各种栖息生境,显著压缩了土著种的栖息空间,进而通过捕食、食物竞争及其他作用途径严重危及土著鱼类种群的续存,提示须采取有力措施限制入侵种的进一步扩散及对濒危土著物种迅速开展人工保育工作。     

Vertical profiles of water and sediment denitrifiers in two plateau freshwater lakes

The present study investigated the abundance, richness, diversity, and community composition of denitrifiers (based on nirS and nosZ genes) in the stratified water columns and sediments in eutrophic Dianchi Lake and mesotrophic Erhai Lake using quantitative PCR assay and high-throughput sequencing analysis. Both nirS- and nosZ denitrifiers were detected in waters of these two lakes. Surface water showed higher nosZ gene density than bottom water, and Dianchi Lake waters had larger nirS gene abundance than Erhai Lake waters. The abundance of sediment nirS- and nosZ denitrifiers in Dianchi Lake was larger than that in Erhai Lake. nirS richness and diversity and nosZ richness tended to increase with increasing sediment layer depth in both lakes. The distinct structure difference of sediment nirS- and nosZ denitrifier communities was found between in Dianchi Lake and Erhai Lake. These two lakes also differed greatly in water denitrifier community structure. Moreover, phylogenetic analysis indicated the presence of several different groups of nirS- or nosZ denitrifiers in both lakes. The novel nirS denitrifiers were abundant in both Dianchi Lake and Erhai Lake, while most of the obtained nosZ sequences could be affiliated with known genera.

     

The status of Lake Lanao endemic cyprinids (Puntius species) and their conservation

The endemic cyprinid species flock of Lake Lanao, Philippines is a classic example of explosive evolution. Based on historical surveys, most of the 18 endemic cyprinid species in Lake Lanao are now believed to be extinct. We compared results of landing and market surveys conducted in 2008 to information from historical surveys. Field sampling and fishermen interviews provided additional information on the status of the endemic and other fish species in Lake Lanao. Puntius lindog and Puntius tumba were the only two endemic species recorded in 2008, accounting for 0.01 % and 0.04 % respectively of the total weight harvested. Our discovery that at least two endemic cyprinids remain in Lake Lanao is surprising and significant as the lake is increasingly imperiled by human disturbances, exploitation and introduced species. Protecting and conserving the remaining endemic species are important management priorities.     

云南湿地生态系统鱼类物种濒危机制初探

湿地生态系统是鱼类生存、繁衍之地。由于云南地理位置特殊,鱼类多样性的研究及保护状况不仅在国内具有重要地位,对下游地区或国家也影响极大。因此,应引起国内、外生物学界和保护组织的高度重视。云南鱼类多样性的特点是：种类丰富、特有类群多;区民分复杂物种类型多样;种群小、数量少。对云南钱的种生存构成威胁的外在因素包括;围湖力沼泽化造成的栖息环境破坏,引种产生的物种生存空间及食物的竞争污染引起的生存环境质量下     

Do human activities raise species richness? Contrasting patterns in United States plants and fishes

In a given area, human activities usually cause the extinction of native species and the establishment of non‐native species. A key conservation issue is whether non‐native establishment tends to outpace native species extinction to produce a net gain in species richness. To determine this, empirical data must be accumulated at various scales. I show that, within the United States, the number of established non‐native plant species per state does tend to outpace the number of extinct and threatened species per state. The net gain in plant species is strongly and positively correlated with human population density. Continuation of this trend predicts substantial gains in net plant species richness for all states in the United States as human population grows. This contrasts with freshwater fishes, where most states show a net loss of species diversity as extinct and threatened species exceed established non‐native species. Changes in fish diversity do not correlate strongly with human population or non‐native species but are largely driven by the decline of native fish species.     

Highlights of large lake research and management in Europe

Lakes in Europe have a bipolar distribution by latitude with higher lake densities in the north (58–65° N) and south (38–48° N). By area, 95% of the large lakes (>100 km²) are located at altitudes lower than 100 m above sea level (ASL) and only 1% lie higher than 1,000 m ASL. Physically large lakes exhibit several similarities to seas and oceans in their thermal structure and circulation dynamics. From the chemical point of view, lakes are important accumulation sites for substances transported from the watershed or built up in the lake itself but they may contribute positively to global greenhouse gas emission. Fauna and flora of ancient large lakes such as the Caspian Sea and Lake Ohrid include large numbers of endemic species, which become endangered if conditions change because of direct human impact, alien species invasions or climate change. Large lakes offer a wide range of ecosystem services to society, the multiple use of which creates multiple pressures on these water bodies such as nutrient load and toxic pollution, modification of hydrology and shore line structure, and shifting of the food web balance by stocking or harvesting various species. Although large lakes are among the best-studied ecosystems in the world, the application to them of environmental regulations such as the European Water Framework Directive is a challenging task and requires that several natural and management aspects specific to these water bodies are adequately considered.     

Effect of landscape factors on fish distribution in arctic Alaskan lakes

1. The distribution of species is affected by many factors operating at a variety of temporal and spatial scales in a heterogeneous landscape. In lakes, fish communities are dynamic, influenced by landscape‐level factors that control colonisation and extinction. 2. We used classification and regression tree (CART) analyses to quantify the importance of landscape‐level factors in determining the distribution of fish species in 168 arctic Alaskan lakes. Factors including lake size, depth, outflow gradient, distance to other lakes, lake order, altitude, river drainage and age of glacial surface were analysed. These factors could affect either access of fish to a lake (colonisation variables), or their survival in a lake that already had been colonised (extinction variables). 3. The presence of a species was predicted accurately in 78.4% ± 10.5% (mean ± SD) of cases, and absence in 75.0% ± 6.1% of cases. The relative importance of extinction versus colonisation variables varied with species. Extinction variables were most important for lake trout (Salvelinus namaycush) and slimy sculpin (Cottus cognatus), a mixture of extinction and colonisation variables was important for arctic char (Salvelinus alpinus), and colonisation variables were most important for arctic grayling (Thymallus arcticus) and round whitefish (Prosopium cylindraceum). 4. Ecological differences among species account for much of the difference in relative importance of colonisation versus extinction variables. In addition, stream piracy events have occurred over geologic time scales, which have resulted in lakes that are currently inaccessible but support relict fish populations. 5. Climate warming, currently occurring in the arctic, is likely to alter further the stream network, which could have dramatic effects on fish distributions by affecting access to isolated lakes or isolating lakes that are currently accessible.