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Stuart Tidey 《BMJ (Clinical research ed.)》1892,1(1633):830-831
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Madeleine St Clair Yewers Devi Stuart‐Fox Claire Alice McLean 《Ecology and evolution》2019,9(1):295-306
Space use including territoriality and spatial arrangement within a population can reveal important information on the nature, dynamics, and evolutionary maintenance of alternative strategies in color polymorphic species. Despite the prevalence of color polymorphic species as model systems in evolutionary biology, the interaction between space use and genetic structuring of morphs within populations has rarely been examined. Here, we assess the spatial and genetic structure of male throat color morphs within a population of the tawny dragon lizard, Ctenophorus decresii. Male color morphs do not differ in morphology but differ in aggressive and antipredator behaviors as well as androgen levels. Despite these behavioral and endocrine differences, we find that color morphs do not differ in territory size, with their spatial arrangement being essentially random with respect to each other. There were no differences in genetic diversity or relatedness between morphs; however, there was significant, albeit weak, genetic differentiation between morphs, which was unrelated to geographic distance between individuals. Our results indicate potential weak barriers to gene flow between some morphs, potentially due to nonrandom pre‐ or postcopulatory mate choice or postzygotic genetic incompatibilities. However, space use, spatial structure, and nonrandom mating do not appear to be primary mechanisms maintaining color polymorphism in this system, highlighting the complexity and variation in alternative strategies associated with color polymorphism. 相似文献
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There are too many kinds of organisms to be able to study and manage each, yet the loss of a single species can sometimes unravel an ecosystem. Such `fusewire species'– critical in the same sense that an electrical fuse can cut out a whole circuit – would be a rewarding focus for research and management effort. However, this approach can only be effective if these `fusewires' represent but a small proportion of the number of species in the system.
To demonstrate methods for measuring what proportion of the species in a system are critical to ecosystem function.
The prevalence of fusewire species was measured in manipulative experiments on an aquatic microcosm.
No single genus deletion caused changes in key characteristics of the system.
Comparison of these results with other published studies shows that the proportion of critical fusewire species varies amongst different ecosystems. The oxidation pond microcosms were shown to contain no single species indispensable to system function. They appear to be ill-suited to a management strategy which focuses on priority eukaryote species. However, a single study provides no evidence that this result is general or even typical of other kinds of ecosystems; it is presented here as an empirical model. Other methods of investigation are available; they are less experimentally rigorous but more practical. These could provide important guidance in planning an approach to management in a particular ecosystem. 相似文献
Aim
To demonstrate methods for measuring what proportion of the species in a system are critical to ecosystem function.
Methods
The prevalence of fusewire species was measured in manipulative experiments on an aquatic microcosm.
Results
No single genus deletion caused changes in key characteristics of the system.
Main conclusions
Comparison of these results with other published studies shows that the proportion of critical fusewire species varies amongst different ecosystems. The oxidation pond microcosms were shown to contain no single species indispensable to system function. They appear to be ill-suited to a management strategy which focuses on priority eukaryote species. However, a single study provides no evidence that this result is general or even typical of other kinds of ecosystems; it is presented here as an empirical model. Other methods of investigation are available; they are less experimentally rigorous but more practical. These could provide important guidance in planning an approach to management in a particular ecosystem. 相似文献
27.
Stuart L. Hart 《Journal of Industrial Ecology》1999,3(4):157-158
Green Chemistry: Theory and Practice, by Paul T. Anastas and John C. Warner
Green Chemistry: Frontiers in Benign Chemical Synthesis and Processes, ed. by Paul T. Anastas and Tracy C. Williamson
Green Chemistry: Designing Chemistry for the Environment, ed. by Paul T. Anastas and Tracy C. Williamson 相似文献
Green Chemistry: Frontiers in Benign Chemical Synthesis and Processes, ed. by Paul T. Anastas and Tracy C. Williamson
Green Chemistry: Designing Chemistry for the Environment, ed. by Paul T. Anastas and Tracy C. Williamson 相似文献
28.
Sympathetic control of cerebral arteries: specialization in receptor type, reserve, affinity, and distribution 总被引:4,自引:0,他引:4
The sympathetic neuroeffector system in the mammalian cerebral circulation has a number of distinctive features that reflect its specialized role in this vascular bed: 1) there is limited alpha-adrenoceptor-mediated contraction in large vessels that becomes progressively less important with branching; 2) contraction is limited by receptor number; small branches often seem to have no functional alpha adrenoceptors; 3) adrenoceptor affinity for norepinephrine is low and so is sensitivity; and 4) the dominant alpha-adrenoceptor subtype differs in different species and may have unique characteristics in some. There is a mechanism of non-alpha-adrenoceptor-mediated contraction involving low-affinity receptor sites--extraceptors--activated by sympathetic nerves. The pig has a seemingly atypical sympathetic mechanism. On the basis of current information the sympathetic neuroeffector mechanisms of the rabbit seem most clearly related to the human. The size, pattern, and distribution of sympathetic control suggest that the role of the sympathetic nerves is to protect the smaller pial arteries against the consequences of sudden increases in sympathetic adrenal discharge. It is not an important mechanism of controlling cerebral blood flow. 相似文献
29.
The Resource Allocation Working Party (RAWP) recognised the need to consider both health authority and primary care services in achieving its objective. RAWP and the subsequent Advisory Group on Resource Allocation (AGRA) found (but did not publish) considerable variation in resources used by both services but could not find a clear relation between them. Statistics provided by the DHSS were used to compare spending by 80 area health authorities in 1980-1 with expenditure per head on general medical services by their corresponding family practitioner committees. There was considerable variation in the provision of resources for both services and no clear relation between the variations in spending on each service. Only 40 of the 80 areas had both health authority and family practitioner committee spending levels within 10% of "target." Subregional inequalities in resources tend to be related to variations in admission rates, which in turn are related to general practitioners'' referral behaviour. These results emphasise the importance of finding out more about inequalities in the provision of general medical services and their relation to the use of hospital services. They also suggest that RAWP''s aim of equality of opportunity of access to health care resources may be achieved only if general medical services are brought into the equation as well. 相似文献
30.
Induction of siderophore activity in Anabaena spp. and its moderation of copper toxicity. 总被引:2,自引:2,他引:0
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Growth of Anabaena sp. strain 7120 (in the absence of chelators or added iron) was inhibited by the addition of 2.1 to 6.5 microM copper and was abolished by copper concentration of 10 microM or higher. When the copper was chelated to schizokinen (the siderophore produced by this organism in response to iron starvation), the toxic effects were eliminated. Analysis of culture filtrates showed that the cupric schizokinen remains in the medium, thereby lowering the amount of copper taken up by the cells. Although this organism actively transports ferric schizokinen, it apparently does not recognize the cupric complex. Thus, Anabaena sp. is protected from copper toxicity under conditions in which siderophore is being produced. For cells grown in low iron, the accumulation of extracellular schizokinen was observed to parallel cell growth and continue well into stationary phase. The actual iron status of the organism was monitored by using iron uptake velocity as an assay. Cultures grown on 0.1 microM added iron were found to be severely iron limited upon reaching stationary phase, thus explaining the continued production of schizokinen. These data show that the siderophore system in Anabaena spp. has developed primarily as a response to iron starvation and that additional functions such as alleviation of copper toxicity or allelopathic inhibition of other algal species are merely secondary benefits. 相似文献