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1.
The effects of temperature and vapour pressure deficit on the flight activity ofSimulium arcticum were defined under controlled laboratory conditions. Optimum conditions of temperature and vapour pressure deficit for flight activity varied with time of exposure to the environmental conditions. By applying polynomial equations for the various response surfaces it was possible to predict the time-dependent, optimal hygrothermal environment for black-fly flight activity. Greatest variability in flight activity occurred just prior to death of the insects. Mortality of flies after 1 h exposures to the experimental conditions occurred only at high temperatures and vapour pressure deficits. With increased time of exposure, mortality increased at lower temperatures and vapour pressure deficits. 相似文献
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Philip C. Withers Christine E. Cooper 《Proceedings. Biological sciences / The Royal Society》2014,281(1784)
It is a central paradigm of comparative physiology that the effect of humidity on evaporative water loss (EWL) is determined for most mammals and birds, in and below thermoneutrality, essentially by physics and is not under physiological regulation. Fick''s law predicts that EWL should be inversely proportional to ambient relative humidity (RH) and linearly proportional to the water vapour pressure deficit (Δwvp) between animal and air. However, we show here for a small dasyurid marsupial, the little kaluta (Dasykaluta rosamondae), that EWL is essentially independent of RH (and Δwvp) at low RH (as are metabolic rate and thermal conductance). These results suggest regulation of a constant EWL independent of RH, a hitherto unappreciated capacity of endothermic vertebrates. Independence of EWL from RH conserves water and heat at low RH, and avoids physiological adjustments to changes in evaporative heat loss such as thermoregulation. Re-evaluation of previously published data for mammals and birds suggests that a lesser dependence of EWL on RH is observed more commonly than previously thought, suggesting that physiological independence of EWL of RH is not just an unusual capacity of a few species, such as the little kaluta, but a more general capability of many mammals and birds. 相似文献
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饥饿是鱼类无法有效获取食物从而使机体呈现能量匮乏的特殊时期, DHA (Docosahexaenoic acid)作为大多数鱼饥饿后得以特别保留的高不饱和脂肪酸, 它对饥饿鱼体可能具有特殊的能量调控作用。为进一步探讨这一问题, 研究设计了以下饲养试验: 先在6%与12%两个油脂水平下分别添加3%DHA制品, 形成基础组、基础-DHA组、高脂组和高脂-DHA组共4组试验饲料。将尾均重为(14.81±0.13) g的鲤360尾随机分为4组, 每组3个重复, 每个重复30尾鱼, 分别用以上4组饲料对进行饲喂, 饲养74d后, 每个养殖缸随机余留6尾鲤(Cyprinus carpio L.)进行饥饿, 36d后检测饥饿鲤体重、生物学性状、体成分、血清生化指标等。结果显示: ①在同一脂肪水平下, DHA添加组饥饿鲤体重减重率均分别显著高于无DHA组(P<0.05); ②在2个油脂水平下DHA添加组饥饿鲤肝细胞直径均分别显著低于无DHA组(P<0.05); 鱼体肥满度、空壳比率等生物学性状在各组饥饿鲤间均无显著差异(P>0.05); ③在2个油脂水平下, DHA添加组饥饿鲤肌肉及肠脂肪含量均分别显著低于无DHA组(P<0.05), 而饥饿鲤肝胰脏脂肪含量在各组间均无显著差异(P>0.05); ④饥饿鲤血清生化指标在各组间均无显著差异(P>0.05)。结果表明, DHA添加组饥饿鲤体重、肝细胞直径以及肌肉及肠脂肪含量均呈显著下降趋势, 显示出DHA的添加未能协助鲤有效抵御饥饿等不良环境的胁迫。 相似文献
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Aim We argue that 'propagule pressure', a key term in invasion biology, has been attributed at least three distinct definitions (with usage of a related term causing additional confusion). All of the definitions refer to fundamental concepts within the invasion process, with the result that the distinct importance of these different concepts has been at best diluted, and at worst lost.
Location Global.
Methods We reviewed pertinent literature on propagule pressure to resolve confusion about different uses of the term 'propagule pressure' and we introduced a new term for one variant, colonization pressure. We conducted a computer simulation whereby the introduction of species is represented as a simple sampling process to elucidate the relationship between propagule and colonization pressure.
Results We defined colonization pressure as the number of species introduced or released to a single location, some of which will go on to establish a self-sustaining population and some of which will not. We subsequently argued that colonization pressure should serve as a null hypothesis for understanding temporal or spatial differences in exotic species richness, as the more species that are introduced, the more we should expect to establish. Finally, using a simple simulation, we showed that propagule pressure is related to colonization pressure, but in a non-linear manner.
Main conclusion We suggest that the nature of the relationship between propagule pressure and colonization pressure, as well as the efficacy of various proxy measures of each, require more detailed exploration if invasion ecology is to continue to develop into a more predictive science. 相似文献
Location Global.
Methods We reviewed pertinent literature on propagule pressure to resolve confusion about different uses of the term 'propagule pressure' and we introduced a new term for one variant, colonization pressure. We conducted a computer simulation whereby the introduction of species is represented as a simple sampling process to elucidate the relationship between propagule and colonization pressure.
Results We defined colonization pressure as the number of species introduced or released to a single location, some of which will go on to establish a self-sustaining population and some of which will not. We subsequently argued that colonization pressure should serve as a null hypothesis for understanding temporal or spatial differences in exotic species richness, as the more species that are introduced, the more we should expect to establish. Finally, using a simple simulation, we showed that propagule pressure is related to colonization pressure, but in a non-linear manner.
Main conclusion We suggest that the nature of the relationship between propagule pressure and colonization pressure, as well as the efficacy of various proxy measures of each, require more detailed exploration if invasion ecology is to continue to develop into a more predictive science. 相似文献
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Aim Conifers are invasive species in many parts of the world, especially in the Southern Hemisphere. There are many introduced conifers in Europe, but their status as alien species is poorly documented. We conducted a comprehensive literature review to ascertain the extent to which alien conifers can be considered invasive. Location Europe. Methods We reviewed the historical record of alien conifer invasion in Europe (i.e. species with a native range outside the continental boundaries of Europe) by screening the DAISIE database and the ISI Web of Science. Results According to DAISIE, there are 54 alien conifer species in Europe. Pseudotsuga menziesii is the species recorded as naturalized in the most countries (12) and the UK is the country with the most naturalized species (18). Thirty‐seven of these conifers have been studied, to some extent, in a total of 131 papers (212 records). Nevertheless, only a few papers have investigated aspects related to biological invasions. In fact, the species are not referred to as alien by the authors in more than half of the papers (66%). Twenty‐five per cent of the papers have investigated plant traits, 46% are about biotic and abiotic factors influencing tree performance and 29% deal with ecological and economic impacts. Most papers are related to entomology, dealing with natural enemies affecting the alien conifers. Main conclusions Scientists have not yet perceived alien conifers in Europe as problematic species. Moreover, the low introduction effort, long lag‐time since plantation and phylogenetic closeness between alien and native conifers are possible reasons for their low expansion in Europe to date. From a management point of view, careful observations of sites with alien conifers is necessary to watch for new invasions. From a scientific perspective, thorough analyses of the extent that introduction, rates of naturalization and biogeographical differences influence invasive spread between the two hemispheres will prove timely. 相似文献
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G E Moore 《Experimental parasitology》1973,33(2):207-211
The DD-136 strain of Neoaplectana carpocapsae is capable of continued movement over dry surfaces at 35 and 5 C if relative humidity (RH) ranges above 90%. It can also live in the field on foliage for several hours at night and up to 24 days in bark beetle tunnels in pine bolts.Further nematode research should be directed toward a few insect species where precipitation and RH are suitable for the dispersion of the dauerlarvae. Such areas in the US are located in the Southeast, Northeast, and on the Northwest Coast. 相似文献
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Franz Essl Dietmar Moser Stefan Dullinger Thomas Mang Philip E. Hulme 《Diversity & distributions》2010,16(6):911-921
Question Are the patterns of alien conifer (Pinaceae, Cupressaceae) invasions different between continents, and how is invasion success influenced by commercial forestry practices? Location Temperate and subtropical countries and regions (n = 60) from five continents spanning both hemispheres. Methods We used generalized linear mixed models to test how continent identity, region area and use in commercial forestry affect probabilities of Pinaceae and Cupressaceae species to escape following introduction and cumulative logit regression models to assess how these predictors affect the likelihood that a species becomes naturalized or invasive. Results Sixty Pinaceae of a global total of 232 and 26 Cupressaceae of a total of 142 species have escaped from cultivation across the study regions examined. Average numbers of both alien Pinaceae and Cupressaceae species per region were highest in Oceania, followed by Africa. Moreover, the probability of alien Cupressaceae and Pinaceae becoming naturalized or invasive was particularly high in these two continents. For both families, species used in commercial forestry have a significantly higher probability of escape than those which are only introduced for ornamental or other purposes. In the case of Pinaceae, forestry species also become naturalized or invasive more frequently than non‐forestry species, while no such effect was detectable for Cupressaceae. Conclusions We found that non‐native conifers are more likely to escape from cultivation, naturalize and turn into invasive weeds on the continents of the Southern Hemisphere. In addition to this biogeographic signal, introduction effort strongly determines the behaviour of introduced Pinaceae, and less so, Cupressaceae. A clear conflict exists between the economic benefits of conifer forestry and the risks to the environment from invasions. Future expansion of commercial forestry should address spatial planning to ecosystems vulnerable to invasion and adopt comprehensive risk assessment procedures. 相似文献
11.
Sandro Bertolino 《Diversity & distributions》2009,15(4):701-708
Aim In this study, a dataset on world-wide squirrel introductions has been used to locate the relative pathways and to determine the factors correlated with species establishment.
Location The world.
Methods The analysis includes a chronological table of introductions, a biogeographical analysis and an assessment of the likelihood of establishment according to species, propagule pressure, area of origin and characteristics of the recipient area.
Results The main vector of such introductions was the intentional importation of live animals. Introductions increased in developed countries and proportionately to the volume of imported mammals. Moreover, areas characterized by higher numbers of native squirrels were more invaded. Squirrels were often introduced deliberately and only to a smaller extent escaped from captivity. The likelihood of their establishment increased proportionately to the number of animals released and decreased proportionately to the increase of the latitudinal distance between the recipient area and the native range of the species. The likelihood that the release of one pair of either Sciurus or Callosciurus species would establish a new population was higher than 50%.
Main conclusion Squirrels proved to be successful invaders and their importation should be restricted so as to prevent further introductions. 相似文献
Location The world.
Methods The analysis includes a chronological table of introductions, a biogeographical analysis and an assessment of the likelihood of establishment according to species, propagule pressure, area of origin and characteristics of the recipient area.
Results The main vector of such introductions was the intentional importation of live animals. Introductions increased in developed countries and proportionately to the volume of imported mammals. Moreover, areas characterized by higher numbers of native squirrels were more invaded. Squirrels were often introduced deliberately and only to a smaller extent escaped from captivity. The likelihood of their establishment increased proportionately to the number of animals released and decreased proportionately to the increase of the latitudinal distance between the recipient area and the native range of the species. The likelihood that the release of one pair of either Sciurus or Callosciurus species would establish a new population was higher than 50%.
Main conclusion Squirrels proved to be successful invaders and their importation should be restricted so as to prevent further introductions. 相似文献
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Aim The enemy release hypothesis is often invoked to explain why some alien plant species become invasive. Here, we investigated relationships between invasiveness, taxonomic isolation and leaf herbivory for tropical alien plant species introduced to a botanical garden in East Africa.
Location Amani Botanical Garden, East Usambara mountains, northeast Tanzania.
Methods We measured the proportion of leaves damaged, and the percentage leaf area damaged on individuals of 28 alien plant species. We extracted data on the presence/absence of native congeners and the number of native confamilial species from an inventory of the East Usambara flora. We also obtained data on planting effort for 26 species, from historical records. Linear and generalized linear models were used to analyse the relationships between invasiveness, herbivory and taxonomic isolation.
Results Mean proportion of leaves damaged per species was significantly explained by taxonomic isolation; proportion of leaves damaged increased with the number of native confamilial species and was greater, on average, for species with native congeners than those without native congeners. The mean percentage of leaf area damaged per species could not be explained by any variables considered in this study. There was no relationship between the degree of herbivory or taxonomic isolation and alien plant species invasiveness, but more-invasive species did have a significantly greater planting effort than less-invasive species.
Conclusions The role herbivores play in controlling alien plant invasions has been investigated relatively little in the tropics. In this study, although the amount of herbivory suffered by alien plants was related to taxonomic isolation, we found no evidence for leaf-feeding invertebrates having a significant role in invasion, suggesting that other factors may be responsible for differences in species success. 相似文献
Location Amani Botanical Garden, East Usambara mountains, northeast Tanzania.
Methods We measured the proportion of leaves damaged, and the percentage leaf area damaged on individuals of 28 alien plant species. We extracted data on the presence/absence of native congeners and the number of native confamilial species from an inventory of the East Usambara flora. We also obtained data on planting effort for 26 species, from historical records. Linear and generalized linear models were used to analyse the relationships between invasiveness, herbivory and taxonomic isolation.
Results Mean proportion of leaves damaged per species was significantly explained by taxonomic isolation; proportion of leaves damaged increased with the number of native confamilial species and was greater, on average, for species with native congeners than those without native congeners. The mean percentage of leaf area damaged per species could not be explained by any variables considered in this study. There was no relationship between the degree of herbivory or taxonomic isolation and alien plant species invasiveness, but more-invasive species did have a significantly greater planting effort than less-invasive species.
Conclusions The role herbivores play in controlling alien plant invasions has been investigated relatively little in the tropics. In this study, although the amount of herbivory suffered by alien plants was related to taxonomic isolation, we found no evidence for leaf-feeding invertebrates having a significant role in invasion, suggesting that other factors may be responsible for differences in species success. 相似文献
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《Journal of Asia》2023,26(4):102137
The human-mediated introduction and movement of alien populations of species within their native range is still a little-explored topic. This phenomenon may cause genetic contamination of local populations and be the introduction pathway of new associated microorganisms and fungi, potentially able to modify the interspecific relationships between insects and host-plants with serious ecological and economic impacts. In the present contribution, we produced the first evidence of a native-alien population of the Palearctic ambrosia beetle Anisandrus dispar occurring in Europe, highlighting that individuals belonging to different populations of a species can disperse via commercial trade within its native biogeographic range resulting in cryptic invasions. Our findings support the idea that the movement of native species within their native distribution range can be more common than previously suspected. 相似文献
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Water suppression in biological NMR is frequently made inefficient by the presence of faraway water that is located near the edges of the RF coil and experiences significantly reduced RF field. WET180 (WET with 180 degrees pulse-toggling) is proposed to cancel the faraway water contribution to the residual solvent signal. The pulse sequence incorporates a modification of the last WET selective pulse to accommodate insertion of a toggled 180 degrees inversion pulse so that the original WET selective pulse angles are effectively preserved. Compared with existing WET methods, WET180 has the advantages of easy implementation, improved residual water suppression, clean spectral phase properties, and good signal intensity retention. WET180 is expected to be most useful in observing resonances close to water in samples containing biological molecules. In addition, the principle of WET180 can be applied in multidimensional experiments to improve residual water suppression and reduce artifacts around water. 相似文献
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Recent theory has suggested a mechanistic relationship between resource availability, competition and invasibility. In a field experiment, in which we manipulated resources and competition, we confirmed that changes in resource availability affected competition intensity, which in turn affected invasibility. We found that fluctuations in resource availability of as short as a few weeks had a large impact on plant invasion success (survival and percentage cover), including up to 1 year following the fluctuations. If resource availability is a primary mechanism controlling invasibility, it may serve as a unifying concept that can integrate earlier ideas regarding invasibility. The results emphasize the important role of history in the invasion process, particularly the occurrence of stochastic, short-lived events that temporarily reduce or suspend competition and increase invasibility. Therefore, it may be very difficult, or even impossible, to reconstruct the ecology of particular invasions after the fact. 相似文献
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Susana Gómez‐González Cristian Torres‐Díaz Graciela Valencia Patricio Torres‐Morales Lohengrin A. Cavieres Juli G. Pausas 《Diversity & distributions》2011,17(1):58-67
Aim We tested the hypothesis that anthropogenic fires favour the successful establishment of alien annual species to the detriment of natives in the Chilean coastal matorral. Location Valparaíso Region, central Chile. Methods We sampled seed rain, seedbank emergence and establishment of species in four paired burned and unburned areas and compared (using GLMM) fire resistance and propagule arrival of alien and native species. To assess the relative importance of seed dispersal and seedbank survival in explaining plant establishment after fire, we compared seed rain and seedbank structure with post‐fire vegetation using ordination analyses. Results Fire did not change the proportion of alien species in the coastal matorral. However, fire increased the number of annual species (natives and aliens) of which 87% were aliens. Fire reduced the alien seedbank and not the native seedbank, but alien species remained dominant in burned soil samples (66% of the total species richness). Seed rain was higher for alien annuals than for native annuals or perennials, thus contributing to their establishment after fire. Nevertheless, seed rain was less important than seedbank survival in explaining plant establishment in burned areas. Main conclusions Anthropogenic fires favoured alien and native annuals. Thus, fire did not increase the alien/native ratio but increased the richness of alien species. The successful establishment of alien annuals was attributable to their ability to maintain rich seedbanks in burned areas and to the greater propagule arrival compared to native species. The native seedbank also survived fire, indicating that the herbaceous community has become highly resilient after centuries of human disturbances. Our results demonstrate that fire is a relevant factor for the maintenance of alien‐dominated grasslands in the matorral and highlight the importance of considering the interactive effect of seed rain and seedbank survival to understand plant invasion patterns in fire‐prone ecosystems. 相似文献
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David R. Thompson Jurgen E. Pohl Yiu-Yu S. Tse Robert W. Hiorns 《International journal of biometeorology》1996,39(3):116-120
Analysis of the time of onset of chest pain in 2254 patients with a myocardial infarction admitted to a coronary care unit in Leicester during a 10-year period shows an association with temperature and humidity. During both the most cold and humid times of the year, the relationship is a strong one. A generalized linear model with a log link was used to fit the data and the backward elimination selection procedure suggested a humid, cold day might help to trigger the occurrence of myocardial infarction. In addition, cold weather was found to have a stronger effect on the male population while those men aged between 50 and 70 years were more sensitive to the effect of high humidity. 相似文献
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A general understanding of biological invasions will provide insights into fundamental ecological and evolutionary problems and contribute to more efficient and effective prediction, prevention and control of invasions. We review recent papers that have proposed conceptual frameworks for invasion biology. These papers offer important advances and signal a maturation of the field, but a broad synthesis is still lacking. Conceptual frameworks for invasion do not require invocation of unique concepts, but rather should reflect the unifying principles of ecology and evolutionary biology. A conceptual framework should incorporate multicausality, include interactions between causal factors and account for lags between various stages. We emphasize the centrality of demography in invasions, and distinguish between explaining three of the most important characteristics by which we recognize invasions: rapid local population increase, monocultures or community dominance, and range expansion. As a contribution towards developing a conceptual synthesis of invasions based on these criteria, we outline a framework that explicitly incorporates consideration of the fundamental ecological and evolutionary processes involved. The development of a more inclusive and mechanistic conceptual framework for invasion should facilitate quantitative and testable evaluation of causal factors, and can potentially lead to a better understanding of the biology of invasions. 相似文献