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J. Timothy Wootton 《PloS one》2012,7(12)
Conservation programs often focus on select species, leading to management plans based on the autecology of the focal species, but multiple ecosystem components can be affected both by the environmental factors impacting, and the management targeting, focal species. These broader effects can have indirect impacts on target species through the web of interactions within ecosystems. For example, human activity can strongly alter riparian vegetation, potentially impacting both economically-important salmonids and their associated river food web. In an Olympic Peninsula river, Washington state, USA, replicated large-scale riparian vegetation manipulations implemented with the long-term (>40 yr) goal of improving salmon habitat did not affect water temperature, nutrient limitation or habitat characteristics, but reduced canopy cover, causing reduced energy input via leaf litter, increased incident solar radiation (UV and PAR) and increased algal production compared to controls. In response, benthic algae, most insect taxa, and juvenile salmonids increased in manipulated areas. Stable isotope analysis revealed a predominant contribution of algal-derived energy to salmonid diets in manipulated reaches. The experiment demonstrates that riparian management targeting salmonids strongly affects river food webs via changes in the energy base, illustrates how species-based management strategies can have unanticipated indirect effects on the target species via the associated food web, and supports ecosystem-based management approaches for restoring depleted salmonid stocks. 相似文献
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The island of Newfoundland is unique because it has as many non-native terrestrial mammals as native ones. The impacts of non-native species on native flora and fauna can be profound and invasive species have been identified as one of the primary drivers of species extinction. Few studies, however, have investigated the effects of a non-native species assemblage on community and ecosystem properties. We reviewed the literature to build the first terrestrial mammal food web for the island of Newfoundland and then used network analyses to investigate how the timing of introductions and trophic position of non-native species has affected the structure of the terrestrial mammal food web in Newfoundland. The first non-native mammals (house mouse and brown rat) became established in Newfoundland with human settlement in the late 15th and early 16th centuries. Coyotes and southern red-backed voles are the most recent mammals to establish themselves on the island in 1985 and 1998, respectively. The fraction of intermediate species increased with the addition of non-native mammals over time whereas the fraction of basal and top species declined over time. This increase in intermediate species mediated by non-native species arrivals led to an overall increase in the terrestrial mammal food web connectance and generality (i.e. mean number of prey per predator). This diverse prey base and sources of carrion may have facilitated the natural establishment of coyotes on the island. Also, there is some evidence that the introduction of non-native prey species such as the southern red-backed vole has contributed to the recovery of the threatened American marten. Long-term monitoring of the food web is required to understand and predict the impacts of the diverse novel interactions that are developing in the terrestrial mammal food web of Newfoundland. 相似文献
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Glacier retreat is occurring across the world, and associated river ecosystems are expected to respond more rapidly than those in flowing waters in other regions. The river environment directly downstream of a glacier snout is characterised by extreme low water temperature and unstable channel sediments but these habitats may become rarer with widespread glacier retreat. In these extreme environments food web dynamics have been little studied, yet they could offer opportunities to test food web theories using highly resolved food webs owing to their low taxonomic richness. This study examined the interactions of macroinvertebrate and diatom taxa in the Ödenwinkelkees river, Austrian central Alps between 2006 and 2011. The webs were characterised by low taxon richness (13–22), highly connected individuals (directed connectance up to 0.19) and short mean food chain length (2.00–2.36). The dominant macroinvertebrates were members of the Chironomidae genus Diamesa and had an omnivorous diet rich in detritus and diatoms as well as other Chironomidae. Simuliidae (typically detritivorous filterers) had a diet rich in diatoms but also showed evidence of predation on Chironomidae larvae. Food webs showed strong species-averaged and individual size structuring but mass-abundance scaling coefficients were larger than those predicted by metabolic theory, perhaps due to a combination of spatial averaging effects of patchily distributed consumers and resources, and/or consumers deriving unquantified resources from microorganisms attached to the large amounts of ingested rock fragments. Comparison of food web structural metrics with those from 62 published river webs suggest these glacier-fed river food web properties were extreme but in line with general food web scaling predictions, a finding which could prove useful to forecast the effects of anticipated future glacier retreat on the structure of aquatic food webs. 相似文献
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SYNOPSIS. New data on resting metabolism, aerobic capacity,respiratory morphology and bimodal breathing capacities offourcaecilian species were combined with previously known data oncaecilian and amphibian biology to discern differing or unifyingthemes of gas exchange within the Gymnophiona and among theAmphibia. Discoveries include 1) a uniform resting metabolismamong caecilians that is distinctly lower than that of anuransand urodeles, 2) an aerobic capacity following activity thatrivals or exceeds that of other amphibians, and 3) despite previoussuggestions to the contrary, a substantial contribution of theskin to respiratory gas exchange, apparently sufficient to sustainthe low resting metabolism. In contrast, pulmonary gas transportappears to dominate during metabolic recovery from exercise,which is comparatively fast. The contributing roles of the skinand lungs to this extreme scope of respiratory needs in caeciliansare further discussed in light of the structural nature of andcirculatory supply to each respiratory bed, and the respiratoryproperties of caecilian blood. 相似文献
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A limnological study was carried out to determine the responses of superoxide dismutase (SOD) activities and soluble protein (SP) contents of 11 common aquatic plants to eutrophication stress. Field investigation in 12 lakes in the middle and lower reaches of the Yangtze River was carried out from March to September 2004. Our results indicated that non- submersed (emergent and floating-leafed) plants and submersed plants showed different responses to eutrophication stress. Both SOD activities of the non-submersed and submersed plants were negatively correlated with their SP contents (P 〈 0.000 1). SP contents of non-submersed plants were significantly correlated with all nitrogen variables in the water (P 〈 0.05), whereas SP contents of submersed plants were only significantly correlated with carbon variables as well as ammonium and Secchi depth (SD) in water (P 〈 0.05). Only SOD activities of submersed plants were decreased with decline of SD in water (P 〈 0.001). Our results indicate that the decline of SOD activities of submersed plants were mainly caused by light limitation, this showed a coincidence with the decline of macrophytes in eutrophic lakes, which might imply that the antioxidant system of the submersed plants were impaired under eutrophication stress. 相似文献
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The movement of energy and nutrients from aquatic to terrestrial ecosystems can be substantial, and emergent aquatic insects can serve as biovectors not only for nutrients, but also for contaminants present in the aquatic environment. The terrestrial predators Tenodera aridifolia sinensis (Mantodea: Mantidae) and Tidarren haemorrhoidale (Araneae: Theridiidae) and the aquatic predator Buenoa scimitra (Hemiptera: Notonectidae) were chosen to evaluate the efficacy of arsenic transfer between aquatic and terrestrial environments. Culex tarsalis larvae were reared in either control water or water containing 1000 µg l−1 arsenic. Adults that emerged from the control and arsenic treatments were fed to the terrestrial predators, and fourth instar larvae were fed to the aquatic predator reared in control or arsenic contaminated water. Tenodera a. sinensis fed arsenic-treated Cx. tarsalis accumulated 658±130 ng g−1 of arsenic. There was no significant difference between control and arsenic-fed T. haemorrhoidale (range 142–290 ng g−1). Buenoa scimitra accumulated 5120±406 ng g−1 of arsenic when exposed to arsenic-fed Cx. tarsalis and reared in water containing 1000 µg l−1 arsenic. There was no significant difference between controls or arsenic-fed B. scimitra that were not exposed to water-borne arsenic, indicating that for this species environmental exposure was more important in accumulation than strictly dietary arsenic. These results indicate that transfer to terrestrial predators may play an important role in arsenic cycling, which would be particularly true during periods of mass emergence of potential insect biovectors. Trophic transfer within the aquatic environment may still occur with secondary predation, or in predators with different feeding strategies. 相似文献
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根据野外调查及相关资料,分析了长江三角洲地区水生植物区系的种类组成、地理成分以及濒危现状.该区现有水生维管植物39科90属185种,其生活型以挺水植物为主(占64.32%),主要分布于田边沟渠、农田以及池塘等不同水体.属、种等级的地理成分分析结果表明:其区系性质主要为温带性质.根据水生植物的濒危现状,参照世界自然保护联盟(IUCN)红色名录的等级和标准(3.1版本),将该区的植物分为9大类,其中地区性灭绝1种,极危种3种,濒危种8种,易危种10种,并简要讨论了该区水生植物受威胁的主要原因. 相似文献
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长江中游地区野生百合资源调查及利用前景 总被引:1,自引:0,他引:1
通过对长江中游地区野生百合资源进行调查,发现长江中游地区有野生百合资源14个种和3个变种即野百合(Lilium brownii F. E. Brown ex Miellez var. brownii)、百合(L. brownii F. E. Brown ex Miellez var. viridulum Baker)、宜昌百合(L. leucanthum (Baker) Baker)、渥丹(L. concolor Salisb. var. concolor)、有斑百合(L. concolor Sali sb. var. pulchellum (Fisch.)Regel)、滇百合(L. baberianum Coll.et Hemsl)、大理百合(L.taliense Franch.)、药百合(L.speciosum Thunb. var. gloriosoides Baker)、湖北百合(L.henryi Baker)、南川百合(L. rosthornii Diels)、宝兴百合(L. duchartrei Franch.)、山丹(L. pumilum DC.)、川百合(L. davidii Duchartre)、条叶百合(L. callosum Sieb. et Zucc.)、乳头百合(L. papilliferum Franch.)、绿花百合(L. fargesii Franch.)和卷丹(L. tigrinum Ker Gawler)。对野生百合在长江中游地区分布现状、观赏特性及开发利用价值进行了分析,为百合新品种培育奠定基础。同时对长江中游地区野生百合资源的保护和合理开发利用提出建议。 相似文献
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Recent research has provided new insight into the physiologyof hibernation in freshwater, marine, and terrestrial turtles.In this paper I review what is known about the mechanisms thatpermit the hearts of these turtles to withstand several monthsof hypoxia or anoxia. I also report new research that indicatesthat a terrestrial turtle, unlike freshwater and marine species,does not experience hypoxia in its winter burrow and thus doesnot rely on glycolysis to supply ATP, at least under moderatewinter conditions. 相似文献
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长江中游草鱼天然种群的生化遗传结构及变异 总被引:25,自引:0,他引:25
采用淀粉或聚丙烯酰胺凝胶电泳方法分析了长江中游武汉江段草鱼天然种群(n=81)中10种同工酶约28个基因座位的遗传变异型。该种群的多态座位比例为16.7%,平均杂合度为0.0739。而Utter和Folmar(1978)曾报道美国的5个草鱼人工繁殖种群的多态座位比例及平均杂合度分别为6%和0.021。比较结果表明,近交很可能是导致草鱼人工繁殖种群中遗传变异性降低的主要原因。我们认为生产上采用数量大、来源广的亲鱼进行人工繁殖,并定期用天然种群更换或补充繁殖用亲鱼很可能是保持或增加鱼类人工繁殖种群遗传变异性的一种有效手段。 相似文献
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A Cartesian diver respirometer was used to measure O₂ uptake and respiratory quotients at 25 C. Respiratory quotients were about 0.70 in starved nematodes, and 0.80 in third-stage and adult nematodes that had fed on bacteria. The energy output as measured by O₂ uptake was inversely related to the concentration of bacteria in the medium, indicating reduction in feeding effort. Feeding bacteria to third-stage nematodes in divers quickly resulted in peak respiration rates averaging 6.4 nl O₂/μg wet weight nematode per hour (QO₂) or six times the endogenous rate. In about 4 hr, the rates fell and then stabilized at a QO₂ of 2.5. Adult males fed bacteria in divers had a peak QO₂ of 2.8 or twice the starved rate. Adult females fed bacteria had a peak QO₂ of 3.7. Starving adult males and third-stage larvae were estimated to lose 2.4% and 1.4%, respectively, of their body weight per day in the form of fat based on the caloric equivalent o f oxygen used and a respiratory quotient of 0.70. The caloric content of the bacteria fed to nematodes in divers was determined. It was then calculated that both third-stage larvae and adult males ingested bacteria equivalent to 4.4 × 10⁻⁵ cal/μg wet weight nematode tissue per hour when feeding. Of the bacterial calories ingested, the larvae used 27% and adults 21% for respiration. It was estimated that males ingested 3.1 × 10⁶ bacteria and females 10 × 10⁶ bacteria during an 8-day life span. 相似文献
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When the Kissimmee River was channelized in the 1960s and 1970s and placed under stage-fluctuation management, the dynamic interactions between the river and the flood-plain were essentially removed. Correspondingly, aquatic invertebrate life in the river and floodplain ecosystem shifted from a riverine to a more lacustrine fauna. A relinkage of the Kissimmee River with the floodplain following restoration will result in numerous changes to such ecologically important factors as streamflow, substrate composition, food quality and quantity, and water quality, all of which will influence invertebrate communities. These factors and their function in the ecosystem as the fauna shifts from predominantly lacustrine back to riverine are presented in a conceptual model. As an integral component of all aquatic ecosystems and a key link between primary producers and higher trophic levels, aquatic invertebrates are a valuable group with which to evaluate the recovery of the Kissimmee River. Utilization of a geographic information system mapping approach linking expected increased habitat heterogeneity and invertebrate richness with restoration efforts is suggested as an economical means of monitoring recovery of the Kissimmee River ecosystem. 相似文献
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长江中下游褶纹冠蚌10个群体CO I基因序列变异分析 总被引:1,自引:0,他引:1
以线粒体CO I基因为分子标记,对长江中下游褶纹冠蚌(Cristaria plicata)10个群体共200个个体的遗传多样性进行了研究.获得了620 bp的同源序列,A+T的平均含量为60.1%,明显高于G+C含量(39.9%),有105个核苷酸变异位点,占全部碱基数的17%,转换和颠换之比达到8.7,检测到了58个单倍型(GenBank登录号:EU698893~EU698950),Hap-5是主体单倍型,占总个体数的41%.褶纹冠蚌鄱阳湖群体(PY)平均核苷酸差异数和核苷酸多样性指数均最高,分别为25.426和0.041 01,太湖群体(TH)和衢州群体(QZ)遗传多样性参数较低.基于群体间遗传距离构建的NJ系统树中,洪泽湖内的3个群体与巢湖群体首先聚为一支,然后与由钱塘江群体、太湖群体、衙州群体和洪湖群体聚成的分支聚在一起,而后与洞庭湖群体聚在一起,最外侧一支为鄱阳湖群体.分子方差分析(AMOVA)得出群体间的遗传分化指数(Fst)为0.208 1(P<0.001),说明我国褶纹冠蚌不同群体间存在一定的遗传分化. 相似文献
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长江中下游黄鳝遗传多样性的微卫星分析 总被引:2,自引:0,他引:2
为了解我国长江中下游地区野生黄鳝(Monopterus albus)的种质资源现状,利用黄鳝微卫星分子标记分析我国长江中下游4个黄鳝野生群体(湖北群体、安徽群体、江苏群体和浙江群体)的遗传多样性水平.通过磁珠富集法获得50个黄鳝徽卫星序列,设计并合成了30对微卫星引物,经筛选得到8对多态性稳定的引物,均为高度多态位点.每对引物扩增得到等位基因数12 -26,平均等位基因数17.4个群体的平均多态信息含量分别为0.804、0.864、0.824和0.736,平均等位基因数分别为9.13、11.00、9.00和7.25,平均期望杂合度分别为0.865、0.918、0.882和0.813,表明4个黄鳝群体遗传多样性丰富,其中安徽群体遗传多样性水平最高,浙江群体相对较低.4个群体间遗传分化指数(FsT)为0.031 2-0.096 5,6.28%的遗传变异存在于群体间,表明4个群体间存在一定的遗传分化.聚类分析显示,浙江群体与安徽群体先聚在一起,再与江苏群体聚为一支,湖北群体单独聚为一支. 相似文献
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Aquatic Versus Terrestrial Feeding Modes: Possible Impacts on the Trophic Ecology of Vertebrates 总被引:3,自引:0,他引:3
On the basis of experimental work, a clear dichotomy in designof the feeding mechanism between aquatic and terrestrial vertebrateshas been found. The aquatic medium combined with suction andthe hydrodynamic tongue offer an unparalleled array of preycapture opportunities for aquatic vertebrates. In the terrestrialfeeding model, prey capture and prey processing require a precisefunctional design to match the nature of the prey. It is proposedthat this dichotomy in basic design would result in fundamentaldifferences in the aquatic and terrestrial paradigms in vertebrateecology. Four hypotheses and their respective supporting evidenceare presented: (1) Increased opportunism, more extensive preyswitching and food overlap are prevalent in aquatic systems;(2) Convergent evolution which is so pervasive in terrestrialfeeding systems is uncommon among aquatic vertebrate feedingsystems; (3) Competition is relaxed and character displacementis absent in aquatic vertebrate feeding systems; and (4) Patternsof diversity in aquatic vertebrate feeding systems defy theterrestrial paradigm. 相似文献