Genetic Basis of Niche Evolution

9707649 Stratton一个生物的基本生态位可以通过性能曲线来量化，将适应度与潜在的资源梯度联系起来。本项目将测量拟南芥适合度反应规范参数在光、水和营养梯度上的遗传变异。这些反应规范形状的遗传变异成分将被估计来检验假设：1)生态位位置的遗传变异多于生态位宽度的遗传变异。2)表现曲线的宽度和最大适应度之间存在负的遗传相关性（万事通就是一无所长）；3)这种权衡在种群间比较中最为明显，而不是在种群内比较。虽然常存遗传变异支配着对自然选择的短期反应，但长期的制约则取决于个体基因座的多效效应。因此，我们将利用重组拟南芥自交系群体对影响适合度反应规范形状的数量性状位点进行定位，以验证资源梯度一端影响适合度的位点对最大适合度或另一端的表现具有负多效效应的假设。种群可以通过改变其生态位位置或增加生态位宽度来应对环境的变化。尽管有很长的理论工作历史，但预测实际群体的反应是一个经验问题，它取决于适应度反应规范参数中遗传变异的数量和模式。最大适应度和适应广度之间的权衡通常是假设的，但很少有文献记载。此外，独立基因座可能影响资源梯度不同末端的表现，这意味着种群可能能够扩大其生态位，而不会对其他环境的表现产生不利影响。

9707649 Stratton The fundamental niche of an organism can be quantified by a performance curve, relating fitness to underlying resource gradients. This project will measure genetic variation in parameters of fitness reaction norms of Arabidopsis thaliana over gradients of light, water, and nutrients. Components of genetic variance for the shape of those reaction norms will be estimated to test the hypotheses that 1) there is more genetic variation for niche position than niche width. 2) that there are negative genetic correlations between the breadth of performance curves and maximum fitness (the jack of all trades is master of none hypothesis) and 3) that such tradeoffs are most apparent in comparisons among populations rather than within. Although the standing genetic variance governs the short-term response to selection, long term constraints depend on pleiotropic effects of individual loci. Thus, quantitative trait loci affecting the shape of fitness reaction norms will be mapped using a recombinant inbred population of Arabidopsis to test the hypothesis 4) that loci which affect fitness at one end of the resource gradient have negative pleiotropic effects maximal fitness or on performance at the other extreme. Populations can respond to changes in the environment by shifting their niche position or by increasing niche breadth. Despite a long history of theoretical work, predicting the response of real populations is an empirical problem which depends on the amount and pattern of genetic variation in parameters of the fitness reaction norm. Tradeoffs between maximal fitness and breadth of adaptation are often assumed but rarely documented. Moreover, the possibility that independent loci affect performance at different ends of the resource gradient means that populations may be able to expand their niche without detrimental effects on performance in other environments.