نتایج جستجو برای: diversification
تعداد نتایج: 20860 فیلتر نتایج به سال:
Understanding the mechanisms and processes that generate biological diversity is a fundamental problem in evolution and ecology. In the past decade, the theory of evolutionary branching and adaptive diversification has provided new perspectives for understanding the evolution of diversity caused by ecological interactions. In models of adaptive diversification, the fitness landscapes change dyn...
A key challenge for biologists is to document and explain global patterns of diversification in a wide range of environments. Here, we explore patterns of continental-scale diversification in a groundwater species-rich clade, the superfamily Aselloidea (Pancrustacea: Isopoda). Our analyses supported a constant diversification rate during most of the course of Aselloidea evolution, until 4-15 Ma...
The species rich butterfly family Nymphalidae has been used to study evolutionary interactions between plants and insects. Theories of insect-hostplant dynamics predict accelerated diversification due to key innovations. In evolutionary biology, analysis of maximum credibility trees in the software MEDUSA (modelling evolutionary diversity using stepwise AIC) is a popular method for estimation o...
In China, income diversification has become a useful method for the rural households to smooth their income and maintain a sustainable mode of consumption. Additionally, income diversification affects rural consumption differently in regions with different income levels. In this paper, I have analyzed the impacts of income diversification on the peasants’ consumption in the Chinese rural areas ...
Diversification represents the idea of choosing variety over uniformity. Within the theory of choice, desirability of diversification is axiomatized as preference for a convex combination of choices that are equivalently ranked. This corresponds to the notion of risk aversion when one assumes the von-Neumann-Morgenstern expected utility model, but the equivalence fails to hold in other models. ...
Very little is known about the influences of corporate strategy and regulation on the risk of regulated firms. The current study addresses this gap by examining the relationship among the level of diversification, the regulatory environment, and risk levels of regulated electric utility companies. Results suggest that both the regulatory environment and level of diversification impact firm risk...
This paper investigates the microeconomics of diversification, based on a two-period model of an owner-managed firm facing uncertainty. The analysis utilizes a general statecontingent representation of uncertainty and learning. Economies of diversification are defined based on a certainty equivalent, which has three components: expected profit, the risk premium (measuring the cost of risk avers...
Diversification rate is one of the most important metrics in macroecological and macroevolutionary studies. Here I demonstrate that diversification analyses can be misleading when researchers assume that diversity increases unbounded through time, as is typical in molecular phylogenetic studies. If clade diversity is regulated by ecological factors, then species richness may be independent of c...
South Asia is gradually diversifying its crop sector in favour of high value commodities, especially fruits, vegetables and spices. If carried out appropriately, diversification can be used as a tool to augment farm income, generate employment, alleviate poverty and conserve precious soil and water resources. In India in the state of West Bengal diversification in cropping pattern is a very rec...
Different models of speciation predict contrasting patterns in the relationship between the dispersal ability of lineages and their diversification rates. This relationship is expected to be negative in isolation-limited models and positive in founder-event models. In addition, the combination of negative and positive effects of dispersal on speciation can result in higher diversification rates...
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