نتایج جستجو برای: population fluctuations
تعداد نتایج: 762077 فیلتر نتایج به سال:
A metapopulation model describing cholera transmission between two communities linked migration was developed and analysed. Disease threshold ratios specific to communities were determined as well as the disease equilibrium points in presence and absence of migration. Sensitivity analysis of the disease thresholds to model parameters was performed using the Latin hypercube sampling scheme to de...
The sex-ratio trait has been described as the production of progenies with unequal sexual proportions induced by meiotic drive. In Drosophila, meiotic drive of the X chromosome against the Y (yielding female biased progenies) is known in several species, including in Drosophila mediopunctata. This species has been previously studied, and the chromosome mechanism of the meiotic drive in sex-rati...
—Effects of 74 episodes of extreme weather on stoppage of population growth and resulting amplitudes of annual population fluctuation of 39 fluctuations of Microtus ochrogaster and 20 fluctuations of M. pennsylvanicus were studied over a 25 y period in eastcentral Illinois. Episodes of extreme weather may have stopped population growth of only six M. ochrogaster fluctuations and of two M. penns...
1. Metapopulation dynamics should be more important at the borders of species distributions due to two main factors: (1) populations are less abundant and fluctuate more at the borders than in the centre of their distributions, and (2) resources in the range margins of species distributions are often more scarce and fragmented. 2. Most metapopulation studies have been performed in a fraction of...
There is large interspecific variation in the magnitude of population fluctuations, even among closely related species. The factors generating this variation are not well understood, primarily because of the challenges of separating the relative impact of variation in population size from fluctuations in the environment. Here, we show using demographic data from 13 bird populations that magnitu...
Population fluctuations and synchrony influence population persistence; species with larger fluctuations and more synchronised population fluctuations face higher extinction risks. Here, we analyse the effect of diet specialisation, mobility, length of the flight period, and distance to the northern edge of the species' distribution in relation to between-year population fluctuations and synchr...
Abstract Two mathematical models of macroevolution are studied. These models have population dynamics at the species level, and mutations and extinction of species are also included. The population dynamics are updated by difference equations with stochastic noise terms that characterize population fluctuations. The effects of the stochastic population fluctuations on diversity and total popula...
sunn pest is considered as the most important insect pest of wheat and barley in iran. different studies have shown that various biotic and abiotic factors affect sunn pest populations. these factors can influence the population density of the pest which in turn can play a role in the control of the pest. in this study the relationship between sunn pest population fluctuations and climatic cond...
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