我国特有种滇螈的绝灭及其基因分析

滇螈是中国特有的两栖类,是云南省二极保护珍稀动物,征求竽云南高原淡水湖泊也,已于２０世纪７０年代末绝迹。绝迹原因主要是”围湖造田”湎水严重污染大搞建筑设施水生生物严重减少以及外一引种,它们的栖息环境,食物,繁殖都受到严重影响,导致最后绝种。     

家畜家禽也会绝种？

一提到保护动物,我们就以为是保护野生动物。其实不然。根据联合国粮农组织的最新报告,家畜家禽也需要保护。随着外来家畜家禽品种的增多,一些地区的"土著"家畜家禽因为没人继续饲养而面临绝种危险,家养动物的多样性随之会遭到破坏,人们餐桌上的美味品种也会随之消失。     

我国东北虎的保护现状与制约因素

东北虎是我国东北森林生态系统的旗舰种和伞护种。20世纪由于受到多种人为活动的影响,东北虎种群数量锐减,分布区严重萎缩。近年来,我国加大对东北虎的保护力度,并取得了一定成效。在部分绝迹分布区再次监测到东北虎活动信息,部分地区种群数量略有上升。本文详细整理并介绍了我国野生东北虎的种群数量和分布特点,分析制约其种群快速增长的因素,对生境丧失、退化和破碎、猎物匮乏及人虎冲突等外在因素进行了综合分析,并从就地保护和易地保护两方面分析了我国东北虎的保护成效及存在的问题,提出进一步保护建议。     

动物小种群的致危因素及其保护浅析

动物小种群的致危因素及其保护浅析龚继恩四川省野生动物资源调查保护管理站成都６１００８１人类对动物栖息环境的改变和破坏,是导致物种濒危和灭绝最主要的原因之一。仅脊椎动物由该原因造成濒危和灭绝的种数,就占其全部濒危和灭绝种数的约２／３。由于人口的不断增加...     

建立基因库挽救濒于绝种的高等植物

据有人统计每年约有200种高等植物绝种。在全部现有的高等植物中有10—20％处于绝种前的危险状态。 为了挽救许多高等植物面临绝种的命运,美国加里福尼亚大学生物系的研究人员提出建立有花植物基因库。他们已经建立了唐菖莆属     

常用濒危中药

人参：五加科植物人参的干燥根及根茎,用于体虚欲脱、惊悸失眠、心力衰竭等症,国家一级保护植物,野生人参已近绝迹。     

开展鸟类调查活动 培养学生综合素质

1　鸟类调查的目的鸟类在维护生态平衡、消灭农林害虫、美化人类生活等方面都起着重要的作用。这是大自然赐予人类的宝贵财富,是我们的朋友。但是近年来,随着环境的严重污染,森林面积的缩小,鸟类的生存已受到严重的威胁,其种群数量正在日益减少,一些珍稀鸟类甚至已到了绝迹的边缘。因此,保护环境,保护鸟类已成了我们责无旁贷的义务。为了培养学生热爱大自然、热爱生物科学的情趣,从小树立保护环境、保护鸟类的信念,提高他们的环保意识,我们组织学生开展了为期1年的鸟类野外调查活动。2　鸟类调查小组的活动2.1　组建鸟类调查小组　把热爱自…     

常用濒危中药

人参：五加科植物人参的干燥根及根茎,用于体虚欲脱、惊悸失眠、心力衰竭等症,国家一级保护植物,野生人参已近绝迹。     

中立型时滞Lotka—Volterra系统解的振动性

一、引言所谓生态系统的持久性就是这个生态系统的所有种群都能长久生存下去.所谓生态系统的灭绝性就是这个生态系统的某一种群遭受毁灭而绝种。当今世界每45分钟就有一个种群绝种或濒临绝种.种群绝种或濒临绝种会破坏生态平衡以致酿成灾难.例如,日118杨正清7卷本船队在南极海城大量捕捞磷虾,首先磷虾被大量捕捞使海     

陕西羽叶报春的人工栽培技术

陕西羽叶报春是百年绝迹、曾被植物界视为已经灭绝或可能灭绝的植物,开展人工栽培研究,对于保护这一极危物种,实现园林开发都具有重要意义。介绍了陕西羽叶报春人工栽培方法,供参考。     

Group selection on the boundary of a stable population

This article presents a model of group selection via differential extinction acting on small boundary populations of a large, fixed population. We restrict consideration to extinction of populations at or near habitat carrying capacity, thus modeling the kind of situation envisioned by Wynne-Edwards (1962). Under the assumption that the extinction rate is large relative to individual genetic parameters, we discuss the effect of differential extinction on the distribution of gene frequencies within boundary micropopulations. In these circumstances, it is shown that differential extinction is most likely to produce a bimodal distribution of the gene frequencies if the form of the extinction operator approximates a step function, with a critical allele frequency at which the extinction rate shifts from high to low. The need for a rather close approximation to such discontinuous behavior limits the possible conditions under which differential extinction might be important. We conclude with a comparison of our model with that of Levins (1970a) and suggest some technically feasible generalizations of our approach.     

The effect of water colour on lake hydrodynamics: a modelling study

1. The one‐dimensional equation solver, PROgram for Boundary layers in the Environment, was used to simulate the temperature structure of Lake Erken, a medium‐sized Swedish lake, assuming differing extinction coefficients for a series of modelled years driven by observed meteorological data and by a set of idealized meteorological data. 2. Results suggested that, as expected, larger extinction coefficients initially led to surface waters becoming warmer. The reverse was true late in the summer, however, as the warming induced by greater absorption of solar radiation was outweighed by the cooling effects of entrained colder hypolimnetic water. 3. There was between a two‐ and fourfold inter‐annual variation in the effects on key physical lake parameters, induced by changing extinction coefficient, such as maximum heat flux, heat content and Schmidt stability. 4. The change in surface heat flux induced by a change in extinction coefficient was up to almost 50 W m⁻². 5. In the summer, changes in extinction coefficient from 0.5 to 0.2 m⁻¹ led to a dramatic shift in the duration of the stratified period as well as to enormous changes in Schmidt stability and hypolimnetic temperature. 6. Future changes to extinction coefficients of small and medium‐sized lakes are likely to have wide‐ranging effects on lake thermal structure and ecology.     

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.     

Annual primary production of phytoplankton in Lake Verkhneye,Schirmacher Oasis,Antarctica

Algal carbon 14 fixation, photosynthetically active radiation (PAR), temperature and nutrients were measured from March 1976 to January 1977 and from November 1983 to February 1984 in a small freshwater lake. As a consequence of the minute meltwater input, the PAR extinction coefficient was very low ranging between 0.04 and 0.12m^–1 throughout the year. Low extinction combined with the transparent and mostly snowless ice cover resulted in high noon PAR intensities of 640–2340 Em^–2s^–1 in the lake from November to January. As a result of the small annual total phosphorus loading (0.01 mmol m^–3 of lake), phosphate concentration in the main water mass did not exceed 0.03 mmol m^–3 during most of the growing season. Phytoplankton assimilation rates were very low with a minimum of 0.03 mgC (mgChl a)^–1 h^–1 in December. The annual net primary production was 0.58 gCm^–2, the lowest value on record. These low levels were due to photoinhibition and phosphorus limitation.     

Species immigration, extinction and turnover of vascular plants in boreal lakes

Dictated by limited resource availability for land acquisition, a central question in conservation biology is the ability of areas of different size to maintain species diversity. The selected reserves should not only be species rich at the moment, but should also maintain species diversity in the long run. We used two sets of data on vascular plant species in boreal lakes collected in 1933/34 and 1996 to test the relationships between lake area and the extinction, immigration and turnover rates of the species. Moreover, we investigated, whether the number of species in 1933/34 or water connection between lakes was related to extinction, immigration and turnover rates of species. We found that lake area or shoreline length was not correlated with immigration or turnover rate. But extinction rate was slightly negatively correlated with shoreline length. The original number of species was positively related to the number of species extinctions and to the absolute turnover rate in the lakes, which indicates that species richness does not create stability in these communities. Species number was not correlated with immigration rate. Upstream water connections in the lakes did not affect immigration, extinction or turnover rates. We conclude that length of the shoreline is a better measure of suitable area for water plants than the lake area, and that because the correlation between shoreline length and extinction rate was slight, also small lakes can be valuable for conservation.     

Status and distribution pattern of black crested gibbon (Nomascus concolor jingdongensis) in Wuliang Mountains, Yunnan, China: implication for conservation

The western black crested gibbon (Nomascus concolor), or black gibbon, one of the lesser apes (Hylobatidae), is mainly distributed in Yunnan, China. Of the four recognized subspecies, N. c. jingdongensis is endemic to the Wuliang Mountain, central Yunnan, China. Of all the subspecies, this one has the largest population of any black gibbon. However, the data were all based on brief estimates. We carried out an extensive field survey on population and group distribution of the black gibbon in the Wuliang Mountains by use of loud morning songs and interviews with local people. Ninety-eight groups were confirmed and located in the mid-montane range of Wuliang Mountains. More groups are found on the east slope and the southern region than in the west and the north. Gibbons are more disjunctly distributed on the west slope, especially in the northern part. Deforestation in the late 1950s, 1960s and 1970s was the main reason for rapid loss of habitat and population decline. Hunting was another key reason for population decline and, in many cases, the main reason for local extinction.     

The annual flood regime as a regulatory mechanism for phytoplankton production in Kainji lake,Nigeria

Phytoplankton production was measured in situ in Kainji lake from December 1970 to September 1972 using the oxygen light and dark bottle technique. Seasonal variations in solar radiation, transparency, temperature, and composition of subsurface light were also measured. Oxygen production per unit area varied from 220 to 4500 mg O₂ m^–2 day^–1, the maximum production rate from 95 to 400 mg O₂ m^–3 h^–1. Seasonal mixing of lake water and river water of varying turbidity changed the optical properties of the lake water and consequently affected phytoplankton production. The annual flood pattern was found to be an important factor regulating phytoplankton production in the lake.     

Light penetrance in lake kinneret

The characteristics of light penetrance in Lake Kinneret, Israel, were observed over the years 1970 to 1973. Light measurements were made concurrently with those of algal speciation and biomass, chlorophyll concentrations and primary production. Vertical extinction coefficients of green light (filter VG9), the most penetrating spectral component, ranged from 0.15 (August 1970) to 0.93 In units m^–1 (April 1970), reflecting the large differences between algal standing crops in non-bloom and bloom seasons. During the dinoflagellate bloom (Peridinium cinctum fa westii) from February through June, the increment of extinction coefficient per unit increase of chlorophyll concentration was 0.006 ln units mg^–1 m². The uneven vertical distribution of algae at this period caused irregularities in the depth curves of light penetrance. At other times, when the phytoplankton cells were more homogeneously dispersed with depth, regular light penetrance curves were observed; however, as previously noted (Rodhe, 1972), attenuation of algal photosynthetic activity often appeared to be regulated by the blue spectral component (filter BG 12). Ratios of absorbed to scattered light in the upper water column ranged from 85:15 to 75:25.     

Are <Emphasis Type="Italic">Hylobates lar</Emphasis> Extirpated from China?

The Nangunhe Nature Reserve in Southwest Yunnan (PRC) has long been presumed to be the last stronghold of lar (or white-handed) gibbons (Hylobates lar) in China and the likely last place of occurrence of Hylobates lar yunnanensis. We conducted a comprehensive survey to assess the status of lar gibbons at Nangunhe. We found no visual or auditory evidence of them still residing at the reserve and therefore tentatively conclude that lar gibbons have become extinct in China. It appears that large-scale destruction of primary forests in the 1960s and 1970s brought about an initial decline in their numbers, and subsequent uncontrolled hunting has resulted in their extirpation. The situation for the six Chinese ape taxa is nothing less than disastrous, with 1 taxon assumed to have become extinct during the last few years, 1 taxon not having been confirmed since the 1980s, and 2 species at the very brink of extinction with only tens of individuals remaining in China.     

Observations and experiments on the phytoplankton of Blelham Tarn, English Lake District

Tubes composed of butyl rubber have been placed in a small English lake in an area where the water is 11-12 m deep. Each tube, when fully distended, contains over 18 000 m³ of water. The tubes are anchored to the shore and lake bottom. A boat can be rowed into them over a specially strengthened portion ofthe margin. The first was installed and its water isolated from that in the lake by the end of July 1970 and the second tube at the beginning of October 1970. The installation, maintenance, and performance of the tubes are described; as are suggested improvements. The temperature regime in the tubes closely follows that in the lake. If the chemical conditions are favourable, the seasonal cycle of Melosira in a tube is similar to that n i the lake. Contamination of the water in the tubes by that in the lake is slight and has a negligible effect on chemical conditions within them. Water can be lost from the tubes under certain conditions. The reverse does not happen. The phytoplankton communities in the tubes are similar in quality to those ofthe lake, even after 2-5 years of separation. The evidence suggests that the tubes are suitable for investigations on certain factors determining the abundance and seasonal cycles of algae in lakes and for other limnological studies.