Same school,different conduct: rates of multiple paternity vary within a mixed‐species breeding school of semi‐pelagic cichlid fish (Cyprichromis spp.)

Mating system variability is known to exist between and within species, often due to environmental influences. An open question is whether, vice versa, similar environmental conditions entail congruent mating behavior, for example in terms of multiple paternity, in species or populations sharing largely comparable breeding modes. This study employed microsatellite markers to investigate the incidence of multiple paternity in Cyprichromis coloratus and Cyprichromis leptosoma, two sympatric, closely related, mouthbrooding Lake Tanganyika cichlids with similar ecological and behavioral characteristics including the formation of open‐water schools. Mouthbrooding females of both species were collected from the same mixed‐species breeding school at the same time, minimizing environmental variation during courtship and mating. In C. coloratus, four of 12 broods had more than one sire, with a mean of 1.33 reconstructed sires per brood. C. leptosoma exhibited multiple paternity in 18 of 22 broods, with a mean of 2.59 or 2.86 reconstructed sires per brood according to the programs gerud and colony , respectively. In addition, two broods were found to contain offspring transplanted from another brood. There was no significant difference in brood size between species, but mean sire number did differ significantly. Hence, substantial similarity in reproductive behavior along with shared environmental conditions during courtship and spawning did not lead to equal rates of polyandry or sneaking in the two species.     

Limnology of Shagawa Lake,Minnesota, prior to reduction of phosphorus loading

Various limnological parameters have been measured in Shagawa Lake, a culturally eutrophic lake in northeastern Minnesota, from 1970–1972. These included temperature; specific conductance; dissolved oxygen; alkalinity; pH; total and orthophosphate phosphorus; nitrate, nitrite and ammonia nitrogen; chlorophyll a; transparency; major cations; and selected trace elements. The lake exhibited many characteristics of high productivity. Concentrations of chlorophyll a reached 60 µg/l during summer months and were reflected in pH values in excess of 9. Anaerobic conditions developed during both summer and winter and, during these intervals, large pools of available nutrients developed in the lower waters. Manganese and iron concentrations varied greatly as a consequence of changes in the oxygen regime. Major cations and other trace elements showed no yearly pattern.     

安徽菜子湖早春开花植物花粉形态及生态意义

采用光学显微镜和扫描电镜对安徽安庆菜子湖早春开花植物15科22种2亚种的花粉形态进行了观察和研究。对这些植物的生态因子,包括地理位置、海拔高度、年降水量、年积温及生境进行了调查和归纳。在此基础上,根据该区域内相同或相似的生态环境条件下分布的现代植物各种花粉类型,间接得出一定花粉类型综合特征所指示的现代气候和环境,为利用菜子湖湖泊孢粉资料来研究区域气候和环境变化提供现代孢粉学资料和依据。     

扁担塘螺类生产力的研究Ⅱ、纹沼螺的周年生产量

采用四种方法对扁担塘纹沼螺的周年生产量进行了测算,结果表明,四种方法得到的生产量吻合极好。生产量的去壳干重和带壳湿重分别是体长频度法,178.07mg     

Litter input from riparian vegetation to streams: a case study of the Njoro River,Kenya

Allochthonous coarse particulate organic matter (CPOM) input into the Njoro River was measured between January and June 1998 at two contrasting sites: open-canopy and closed-canopy sites. Bank runoff and aerial drift traps were used for collecting CPOM inputs over periods of two weeks. Collected litter was sorted into four categories: leaves, fruits, wood and plant fragments. Monthly input ranged from 77 to 228 g ash free dry weight m^–1 for bank runoff input and from 64 to 129 g ash free dry weight m^–2 for aerial input. The highest input of 228 g ash free dry weight m^–1 was recorded in May at the closed-canopy site. Wood, fruits and plant fragments of particle size >100 m contributed a mean ± SE of 60±9% of the total inputs with the rest from leaf litter. The closed-canopy site had higher inputs (P<0.05) of bank and aerial input than the open canopy site. There was no relationship between total bank runoff input and rainfall (r _s = 0.08), however, total aerial input increased with decrease in rainfall (r _s = – 0.59). There were differences between inputs from different plant species (P<0.05) that ranked in the following order: Syzygium cordatum > Rhus natalensis > Pittosporum viridiflorum > Vangueria madagascariensis. Removal of riparian vegetation from the banks of the Njoro River would alter the quantity and quality of the litter and reduce CPOM inputs to the river and to a downstream lake with attendant consequences to the energy budget of biocoenoses in the two ecosystems.     

Lake macroinvertebrate assemblages and relationship with natural environment and tourism stress in Jiuzhaigou Natural Reserve,China

With increasing human population and urbanization, tourism in natural reserves and other protected lands is growing. It is critical to monitor and assess the impacts of tourism on ecosystem health. However, there is a general lack of information on biological communities in natural reserves of developing countries and of tools for assessing human impacts. In the present study, we investigated macroinvertebrate assemblages in nine lakes in Jiuzhaigou Natural Reserve of China. Both benthic (20 dips of D-net) and light-trap samples (2 h) were collected at each lake and all benthic specimens and adults of Ephemeroptera, Plecoptera, and Trichoptera (EPT) were identified and counted. Water temperature and water quality variables were measured on site or in the Lab. Seventy taxa were recorded and dominated by dipterans and caddisflies. Light traps contributed 47% of taxa richness and 66% of EPT richness at the lakes. Detrended Correspondence Analysis showed that water temperature and tourism index were strongly associated with the changes of assemblage composition. Taxa richness and EPT richness calculated for the composite samples (benthic + light trap) were well fit with Poisson generalized linear model (adjusted R² = 0.83 and 0.85, respectively), generally decreasing with increasing elevation, tourism index, and total-N. Tourism index was ranked as the top predictor for EPT richness based on multiple model weights, and elevation for taxa richness. In comparison, when based on benthic samples, neither of the metrics could be fitted with the seven environmental variables selected. These findings highlight the benefit of combined use of the sampling methods for lake monitoring and offered an analytical guide to developing biological indicators of lake ecosystem health in protected areas.     

哈拉海湿地丹顶鹤现状、受胁原因及保护

2000年4月至5月对哈拉海湿地丹顶鹤的数量、分布、现状进行了调查,共统计到迁徙丹顶鹤120只次,丹顶鹤夏季种群为14只;其中繁殖个体为10只,另有4只亚成体,此外对本区丹顶鹤受胁原因进行了分析并提出了保护措施。     

Abstracts of papers read at the winter meeting at the university of Newcastle Upon Tyne

Young plants of Laminaria hyperborea collected from the field were grown for 2·5–4 weeks in blue, green, red and white (simulated underwater) light fields at 5, 20 and 100 μmol m^-2s^-1. The absolute concentrations of all pigments showed little variation with irradiance in green and white light, but decreased in high irradiances of red and blue light. The ratio of fucoxanthin to chlorophyll a also increased in the latter treatments, as did the chlorophyll c:a ratio in bright red light. There was little difference in the action spectrum for photosynthesis between the different light qualities at any one irradiance, but the action spectra for plants grown at 100 μmol m^-2s^-1 showed deeper troughs and higher peaks than those for plants grown at lower irradiances. Gross photosynthesis per unit of thallus area at 10 μmol m^-2s^-1 decreased in plants with low total pigment concentrations, but the photosynthesis per unit of pigment concentration increased. This suggestion of self-shading of pigment molecules within the algal thalli was supported by a flattening of the action spectrum in plants with higher chlorophyll a contents. The variations observed between the action spectra for different plants could thus be attributed to the decrease in pigment content at high irradiances, and not to the light quality in which the plants were grown.     

鄱阳湖湿地灰化苔草种群生产力特征及其水文响应

淡水湖泊湿地中,水文条件是影响湿地植物分布和生长发育的关键因素,研究特定湿地植物种群与水文变化之间关系,对于认识湿地植被格局形成及进行湿地生态调控与恢复具有重要意义。选取鄱阳湖湿地洲滩优势植物——灰化苔草(Carex cinerascens)种群作为研究对象,基于野外实地观测数据,研究不同高程带灰化苔草春草种群生产力特征及其对水文变化的响应。结果表明:春草生长季内各高程带灰化苔草种群变化规律基本一致,但其生长发育过程对水文条件产生差异性反应,长期连续水淹和半水淹条件抑制灰化苔草的生长,而间歇性半水淹和未水淹条件则促进灰化苔草伸长生长和生物量积累;生长初期灰化苔草通过储水策略应对水分缺乏形成的干旱胁迫,而生长末期则通过增加干物质含量来应对淹水胁迫;灰化苔草定植与生长发育需要一定的水文条件,淹没期平均水深3.70—2.78 m、淹没频率42.08%—43.17%、平均距湖水面高度-0.23—0.77 m的水文环境更有利于灰化苔草的生长发育。研究结果可为未来鄱阳湖湿地植被保护和湖泊水位调控提供重要参考依据。     

Contrasting geographic structure in evolutionarily divergent Lake Tanganyika catfishes

Geographic isolation is suggested to be among the most important processes in the generation of cichlid fish diversity in East Africa's Great Lakes, both through isolation by distance and fluctuating connectivity caused by changing lake levels. However, even broad scale phylogeographic patterns are currently unknown in many non‐cichlid littoral taxa from these systems. To begin to address this, we generated restriction‐site‐associated DNA sequence (RADseq) data to investigate phylogeographic structure throughout Lake Tanganyika (LT) in two broadly sympatric rocky shore catfish species from independent evolutionary radiations with differing behaviors: the mouthbrooding claroteine, Lophiobagrus cyclurus, and the brood‐parasite mochokid, Synodontis multipunctatus. Our results indicated contrasting patterns between these species, with strong lake‐wide phylogeographic signal in L. cyclurus including a deep divergence between the northern and southern lake basins. Further structuring of these populations was observed across a heterogeneous habitat over much smaller distances. Strong population growth was observed in L. cyclurus sampled from shallow shorelines, suggesting population growth associated with the colonization of new habitats following lake‐level rises. Conversely, S. multipunctatus, which occupies a broader depth range, showed little phylogeographic structure and lower rates of population growth. Our findings suggest that isolation by distance and/or habitat barriers may play a role in the divergence of non‐cichlid fishes in LT, but this effect varies by species.