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本研究对1931~2009年间分离于中国20个省区的167株狂犬病病毒的N基因序列进行进化分析,以探讨中国狂犬病病毒株的基因分型和分组情况、时间和空间的动态进化。结果显示:从中国分离的毒株都属于基因1型狂犬病病毒,可以分为2个进化分支共计8个组,分支Ⅰ包括1~4组,分支Ⅱ包括5~8组;选择压力分析表明中国狂犬病病毒处于较强的净化选择约束下,狂犬病病毒N基因中的核苷酸突变主要是同义突变;运用贝叶斯中的马尔科夫链的蒙特卡洛方法估计中国狂犬病病毒N基因核苷酸的平均碱基替代率为4×10-4替代/位点/年,共同祖先出现的时间不超过2000年前;迁移分析表明中国狂犬病病毒株存在跨地域传播。 相似文献
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Most species of rotifers have a combination of sexual and asexual reproduction, with sexual reproduction resulting in resting
eggs, which can lay dormant for long periods. The occurrence of sexual reproduction affects population dynamics through the
temporary presence of male rotifers, and a reduction in the growth of the number of female rotifers. A previously published,
individual-based model used dynamic energy budget theory to describe rotifer food intake, growth, egg production, and mortality,
but assumed asexual reproduction only. In the current study, we have expanded the model to describe the entire reproductive
cycle of the rotifers, making it usable for investigating relationships, such as those between the signal triggering mictic
egg production, and the timing and number of resting eggs produced. The model is intended for use in predicting the specific
future development of cultures, for instance, as a process model in rotifer or resting egg production for aquaculture.
Guest editors: S. S. S. Sarma, R. D. Gulati, R. L. Wallace, S. Nandini, H. J. Dumont & R. Rico-Martínez
Advances in Rotifer Research 相似文献
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The synchronization of the dynamics of spatially subdivided populations is of both fundamental and applied interest in population biology. Based on theoretical studies, dispersal movements have been inferred to be one of the most general causes of population synchrony, yet no empirical study has mapped distance-dependent estimates of movement rates on the actual pattern of synchrony in species that are known to exhibit population synchrony. Northern vole and lemming species are particularly well-known for their spatially synchronized population dynamics. Here, we use results from an experimental study to demonstrate that tundra vole dispersal movements did not act to synchronize population dynamics in fragmented habitats. In contrast to the constant dispersal rate assumed in earlier theoretical studies, the tundra vole, and many other species, exhibit negative density-dependent dispersal. Simulations of a simple mathematical model, parametrized on the basis of our experimental data, verify the empirical results, namely that the observed negative density-dependent dispersal did not have a significant synchronizing effect. 相似文献
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A large body of theoretical studies has shown that synchrony among populations is critical for the long-term persistence of species in fragmented habitats. Although the effects of dispersal and environmental factors on synchrony have been investigated theoretically, empirical studies of these relationships have been lacking. We explored the interplay between environmental and demographic factors (fecundity, survival, dispersal) on population synchrony for 53 species of birds. We show that the interspecific differences in mean synchrony were determined by global environmental factors whose action was probably mediated by the abundance of each species. After removing the effect of these global factors on synchrony, the residual synchrony was strongly correlated with dispersal distance. The relationship between dispersal and synchrony was stronger for the species nesting in wet habitats than for those nesting in dry habitats. Our results indicate that different factors synchronize bird populations at different spatial scales, thus highlighting the role of scale in understanding spatial population dynamics and extinction risks. 相似文献
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It is well established that plants and soil properties are interdependent. What is less known is the degree to which the distribution of plant and soil properties, in both space and time, match one another. We assessed plant community and soil conditions in permanent sample plots in a tallgrass prairie community from 2002 to 2008. Redundancy analysis showed that the dominant grass species were associated with changes in elevation, soil pH, and gravimetric water content, but not nitrogen or phosphate. Indicator species analysis suggested the community is best described by four cluster types, with half of the plots changing community type over the 6-year sampling period. These cluster types were generally spatially aggregated, with semivariograms showing a range from 80 to 346 m. This degree of spatial structuring was observed in the elevation and soil water content data, but not in measures of soil inorganic N or P. This suggests that natural plant communities do not necessarily show a strong correspondence to all soil variables, especially those that vary rapidly in time and space. The dynamic nature of vegetation patch distribution, combined with their size, may contribute to the loss of species from small tallgrass prairie reserves. 相似文献
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Robert BIEDERMANN 《Entomological Science》2007,10(3):217-222
The patterns of synchrony in the population fluctuations of six species of gall‐makers on oak (Hymenoptera, Cynipidae and Diptera, Cecidomyiidae) were analyzed over a small‐scale transect (8 km) and a large‐scale transect (500 km). Gall‐maker species differed in their degree of synchrony. At the small scale some species showed synchrony among local sites, whereas at the large scale, with one exception, population fluctuations of all species were largely independent. The patterns of synchrony differed between the two spatial scales. At the small scale a considerable degree of synchrony was found among sites for two species, Cynips divisa and Neuroterus quercusbaccarum, whereas at the large scale no synchrony was seen for these species. For one species, Macrodiplosis volvens, the fluctuations were asynchronous at both the small and large scales. At the large scale, synchrony among sites was found for one species: the fluctuations of Neuroterus anthracinus were largely synchronous at both scales (i.e. over several hundred kilometers). Distance‐dependent synchronies (i.e. decreasing synchrony with increasing distance) were found for only one species, Neuroterus anthracinus. In summary, the levels of synchrony in the population fluctuations of these insects differed among species and were scale‐dependent. Scaling up from the small scale to the large scale does not seem appropriate. 相似文献
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Tim Coulson† Steve Albon‡ Jill Pilkington§ Tim Clutton-Brock¶ 《The Journal of animal ecology》1999,68(4):658-671
1. The scale at which population dynamics are analysed is important, as results from analyses at different spatial scales can differ and affect interpretation.
2. In this study, detailed census data collected over a 10-year period from a population of Soay sheep ( Ovis aries L.) on the Island of Hirta in the St Kilda archipelago, Scotland, is used, together with cluster analysis, to distinguish a temporally stable spatial substructure.
3. Structured demographic accounting of the variance in population change (SDA) is also used to analyse the dynamics of the whole population treated as (a) one unit; (b) one unit subdivided into three subunits; and (c) three independent units.
4. Differences in survival, recruitment and dispersal rates are demonstrated between divisions of the population, which are probably associated with variation in grazing quality.
5. If these groups were not coupled by dispersal and density-independent entrainment, the population dynamics of the three groups would diverge, however, the dynamics of the three subunits are strongly correlated. 相似文献
2. In this study, detailed census data collected over a 10-year period from a population of Soay sheep ( Ovis aries L.) on the Island of Hirta in the St Kilda archipelago, Scotland, is used, together with cluster analysis, to distinguish a temporally stable spatial substructure.
3. Structured demographic accounting of the variance in population change (SDA) is also used to analyse the dynamics of the whole population treated as (a) one unit; (b) one unit subdivided into three subunits; and (c) three independent units.
4. Differences in survival, recruitment and dispersal rates are demonstrated between divisions of the population, which are probably associated with variation in grazing quality.
5. If these groups were not coupled by dispersal and density-independent entrainment, the population dynamics of the three groups would diverge, however, the dynamics of the three subunits are strongly correlated. 相似文献
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The dynamics of a population inhabiting a heterogeneous environment are modelled by a diffusive logistic equation with spatially varying growth rate. The overall suitability of an environment is characterized by the principal eigenvalue of the corresponding linearized equation. The dependence of the eigenvalue on the spatial arrangement of regions of favorable and unfavorable habitat and on boundary conditions is analyzed in a number of cases.Research supported by National Science Foundation grant #DMS 88-02346 相似文献
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The two main approaches in theoretical population ecology-the classical approach using differential equations and the approach using individual-based modeling-seem to be incompatible. Linked to these two approaches are two different timescales: population dynamics and behavior or physiology. Thus, the question of the relationship between classical and individual-based approaches is related to the question of the mutual relationship between processes on the population and the behavioral timescales. We present a simple protocol that allows the two different approaches to be reconciled by making explicit use of the fact that processes operating on two different timescales can be treated separately. Using an individual-based model of nomadic birds as an example, we extract the population growth rate by deactivating all demographic processes-in other words, the individuals behave but do not age, die, or reproduce. The growth rate closely matches the logistic growth rate for a wide range of parameters. The implications of this result and the conditions for applying the protocol to other individual-based models are discussed. Since in physics the technique of separating timescales is linked to some concepts of self-organization, we believe that the protocol will also help to develop concepts of self-organization in ecology. 相似文献
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Aim The study and prediction of species–environment relationships is currently mainly based on species distribution models. These purely correlative models neglect spatial population dynamics and assume that species distributions are in equilibrium with their environment. This causes biased estimates of species niches and handicaps forecasts of range dynamics under environmental change. Here we aim to develop an approach that statistically estimates process‐based models of range dynamics from data on species distributions and permits a more comprehensive quantification of forecast uncertainties. Innovation We present an approach for the statistical estimation of process‐based dynamic range models (DRMs) that integrate Hutchinson's niche concept with spatial population dynamics. In a hierarchical Bayesian framework the environmental response of demographic rates, local population dynamics and dispersal are estimated conditional upon each other while accounting for various sources of uncertainty. The method thus: (1) jointly infers species niches and spatiotemporal population dynamics from occurrence and abundance data, and (2) provides fully probabilistic forecasts of future range dynamics under environmental change. In a simulation study, we investigate the performance of DRMs for a variety of scenarios that differ in both ecological dynamics and the data used for model estimation. Main conclusions Our results demonstrate the importance of considering dynamic aspects in the collection and analysis of biodiversity data. In combination with informative data, the presented framework has the potential to markedly improve the quantification of ecological niches, the process‐based understanding of range dynamics and the forecasting of species responses to environmental change. It thereby strengthens links between biogeography, population biology and theoretical and applied ecology. 相似文献
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Spiders are important generalist predators in natural pest control. However, agricultural fields are highly disturbed and ephemeral habitats, which present a number of challenges to the organisms living there; likewise landscape diversity and heterogeneity are also thought to be important factors in determining spider spatial dynamics. To investigate the interactions between these factors, we present an individual-based simulation model, which integrates life history characteristics of a typical agrobiont linyphiid spider with a dynamic spatially explicit landscape representation. The landscape contains several habitat types of varying quality and varies in time and space. Simulations showed that spatial landscape diversity (number of habitat types available for the spiders) is crucial for the persistence of spiders, but that spatial heterogeneity (spatial arrangement of patches) only had little impact on spider abundance. The necessary landscape diversity could either be provided by a diverse crop rotation or by including refuges in the form of less frequently managed habitats in the landscape. The presence of refuges greatly boosted numbers of spiders in the landscape as a whole. The most important characteristics of refuge were sanctuary from pesticides and extra prey availability, whereas tillage frequency mattered less. The simulations indicated that agrobiont linyphiids combination of high dispersal abilities and high reproductive rate enables it to exploit the transient resources of the different habitats in the agricultural landscape. 相似文献
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Toshinori Okuyama 《Theoretical Ecology》2015,8(3):327-331
Theoretical models of parasitoid-host dynamics predict that egg limitation in parasitoids destabilizes community dynamics. However, although egg limitation is experienced by individual parasitoids with variable success of encountering hosts, such details were neglected in previous models. This study developed an individual-based parasitoid-host model that explicitly incorporates egg limitation and host encounters of individual parasitoids. The model indicates that the combination of egg limitation and variation in the success of encountering hosts stabilizes parasitoid-host dynamics. The stabilizing mechanism emerges from Jensen’s inequality because egg limitation makes the number of offspring inherently concave down in the number of encountered hosts. Reasons for the inconsistent predictions of the effect of egg limitation between the current model and previous models are discussed. 相似文献
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Considerable variation in morphology associated with resource use is a classic example of local adaptation to the environment. We demonstrate that a temporal change in feeding morphology might occur within a population. In a 5-year natural field experiment, we estimated gill raker morphology, resource density and population dynamics of the roach and its competitor, the perch. Despite a variation in density of zooplankton resources and perch across years, no change in roach density was observed. However, gill raker morphology in roach covaried with size structure of the zooplankton resource across years. A laboratory experiment confirmed that gill raker morphology has a great effect on roach foraging efficiency on zooplankton and that there is a functional trade-off with regard to zooplankton foraging. We suggest that the response in gill raker structure is an adaptation to deal with the rapid population dynamics of zooplankton, which are in turn mediated by changes in the size structure of the competing perch. 相似文献
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城市景观空间自相关与自相似的尺度特征研究 总被引:5,自引:3,他引:5
在RS与GIS技术支持下,以上海市外环以内城市中心区为区域背景,研究城市景观格局空间自相关与分形结构在不同粒度下的变化特征,揭示其对粒度的响应特征和敏感程度。结果表明,城市景观格局的空间自相关性和自相似性依赖于粒度的选择,MoranⅠ与各种景观类型的分维数均存在尺度效应;城市景观格局空间自相关性与自相似性在一定尺度范围内具有尺度依赖性,但二者对尺度的依赖程度不同。空间自相关性具有较高的尺度依赖性;而不同景观类型的自相似性随尺度的变化没有统一规律;城市景观格局的空间自相关性和自相似性对尺度变化的敏感点不同。居住景观的MoranⅠ对尺度变化的敏感点为50m,其他景观类型无明显的敏感点;分维数对尺度的敏感点因景观类型不同而异。 相似文献