Adaptive Diversification Due to Resource Competition in Sexual Models

2016 ◽  
pp. 74-112
Author(s):  
Michael Doebeli

This chapter focuses on evolutionary branching in niche position due to frequency-dependent competition. When the majority phenotype of a population is competing for one type of resource, selection may favor minority phenotypes that consume different types of resources, which could result in phenotypic differentiation and divergence. The idea of divergence due to competition is also the basis for the well-known concept of ecological character displacement, although here the focus is not so much on the origin of diversity arising in a single species, but rather on the evolutionary dynamics of existing diversity between different and already established species. Ecological character displacement embodies the possibility that competition between species can drive divergence in characters determining resource use. However, there are alternative evolutionary scenarios for phenotypic diversification. In the context of resource competition, one such alternative is that individuals diversify their diet by evolving a wider niche.


Author(s):  
Michael Doebeli

This chapter examines evolutionary branching in sexual populations. As sexual populations converge to what would be a branching point in clonal models, splitting obviously becomes a problem, because mating between different marginal phenotypes generally creates intermediate phenotypes. Through segregation and recombination, sexual reproduction can prevent the establishment of diverging phenotypic clusters in randomly mating populations. To allow for a phenotypic split, mating needs to be assortative with respect to the ecological trait that is under disruptive selection. Thus, the question of evolutionary branching in sexual populations, that is, of adaptive speciation, is intimately tied to questions about the evolution of assortative mating. If evolutionary branching occurs in sexual populations due to the presence of assortative mating mechanisms, the diverging phenotypic clusters will show prezygotic reproductive isolation at least to some extent, and hence they can be viewed as representing incipient species.


Author(s):  
Sophia Kalantzakos

In 2010, because of a geopolitical incident between China and Japan, seventeen elements of the periodic table known as rare earths became notorious overnight. An “unofficial” and temporary embargo of rare-earth shipments to Japan alerted the world to China’s near monopoly position on the production and export of these indispensable elements for high-tech, defense, and renewable energy sources. A few months before the geopolitical confrontation, China had chosen to substantially cut export quotas of rare earths. Both events sent shockwaves across the markets, and rare-earth prices skyrocketed, prompting reactions from industrial nations and industry itself. The rare-earth crisis is not a simple trade dispute, however. It also raises questions about China’s use of economic statecraft and the impacts of growing resource competition. A detailed and nuanced examination of the rare-earth crisis provides a significant and distinctive case study of resource competition and its spill-over geopolitical effects. It sheds light on the formulation, deployment, longevity, effectiveness, and, perhaps, shortsightedness of policy responses by other industrial nations, while also providing an example of how China might choose to employ instruments of economic statecraft in its rise to superpower status.


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