نتایج جستجو برای: diversification

تعداد نتایج: 20860  

Journal: :Systematic biology 2016
Kenneth H Kozak John J Wiens

Understanding which traits drive species diversification is essential for macroevolutionary studies and to understand patterns of species richness among clades. An important tool for testing if traits influence diversification is to estimate rates of net diversification for each clade, and then test for a relationship between traits and diversification rates among clades. However, this general ...

2010
James A. Fordyce

BACKGROUND Phylogenetic hypotheses are increasingly being used to elucidate historical patterns of diversification rate-variation. Hypothesis testing is often conducted by comparing the observed vector of branching times to a null, pure-birth expectation. A popular method for inferring a decrease in speciation rate, which might suggest an early burst of diversification followed by a decrease in...

2012
Wenhua Yu Junxiao Xu Yi Wu Guang Yang

Although mammals have long been regarded as a successful radiation, the diversification pattern among the clades is still poorly known. Higher-level phylogenies are conflicting and comprehensive comparative analyses are still lacking. Using a recently published supermatrix encompassing nearly all extant mammalian families and a novel comparative likelihood approach (MEDUSA), the diversification...

2000
Andy Naranjo

Using a database of more than 8,000 companies from 35 countries, we find that the value of corporate diversification is negatively related to the level of capital market development. Among high-income countries, where capital markets are well developed, we find a significant diversification discount. By contrast, for the lower income countries, we find that there is either no diversification di...

2006
Daniel L Rabosky

Rates of species origination and extinction can vary over time during evolutionary radiations, and it is possible to reconstruct the history of diversification using molecular phylogenies of extant taxa only. Maximum likelihood methods provide a useful framework for inferring temporal variation in diversification rates. LASER is a package for the R programming environment that implements maximu...

2008
Sanzidur Rahman

This study aimed at examining the merit of crop diversification as a strategy for agricultural growth in Bangladesh. Specifically, the existence of economies of diversification, scale economies and diversification efficiencies at the farm level were examined using a stochastic input-distance function approach. Results reveal strong evidence of diversification economies amongst most crop enterpr...

Journal: :Proceedings. Biological sciences 2008
Daniel L Rabosky Irby J Lovette

Evidence from both molecular phylogenies and the fossil record suggests that rates of species diversification often decline through time during evolutionary radiations. One proposed explanation for this pattern is ecological opportunity, whereby an initial abundance of resources and lack of potential competitors facilitate rapid diversification. This model predicts density-dependent declines in...

2016
Eric Lewitus Hélène Morlon

Identifying modes of species diversification is fundamental to our understanding of how biodiversity changes over evolutionary time. Diversification modes are captured in species phylogenies, but characterizing the landscape of diversification has been limited by the analytical tools available for directly comparing phylogenetic trees of groups of organisms. Here, we use a novel, non-parametric...

Journal: :Ecology letters 2008
Roland Jansson T Jonathan Davies

We used the largest DNA-based phylogeny of flowering plants to date to evaluate the importance of energy vs. past climate change in predicting global patterns in diversification. Relative diversification rates increased towards the equator, suggesting that differences in per-lineage net diversification may be an important component of the latitudinal diversity gradient. The amplitude of Quatern...

Journal: :Evolution; international journal of organic evolution 2012
Hélène Morlon Brian D Kemps Joshua B Plotkin Dustin Brisson

The current diversity of life on earth is the product of macroevolutionary processes that have shaped the dynamics of diversification. Although the tempo of diversification has been studied extensively in macroorganisms, much less is known about the rates of diversification in the exceedingly diverse and species-rich microbiota. Decreases in diversification rates over time, a signature of explo...

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