Testing limits to adaptation along altitudinal gradients in rainforest Drosophila
Testing limits to adaptation along altitudinal gradients in rainforest Drosophila
复制标题
DOI：
10.1098/rspb.2008.1601
复制
发表时间：
2009-04-22
影响因子：
4.7
通讯作者：
Kennington, W. Jason
中科院分区：
文献类型：
--
作者：
Bridle, Jon R.;Gavaz, Sedef;Kennington, W. Jason
既然进化可以使一个物种的生态容忍度发生迅速而剧烈的变化，那么是什么阻止了种群适应扩张到其分布边缘的新栖息地呢？最近的种群遗传模型关注的是种群间迁移的相对成本和收益。一方面，迁移可能通过阻止局部种群匹配其局部选择最优来限制适应性分化。另一方面，迁徙也可能导致必要的遗传变异，使种群能够追踪这些变化的最优状态。在自然情况下基因流动的这些对比效应的经验证据是缺乏的，很大程度上是因为它仍然难以获得。在这里，我们开发了一种方法来探索理论模型，通过估计遗传差异的性状，赋予抗逆性在热带雨林果蝇沿着类似的生态梯度。这种方法允许测试临床差异与局部密度的耦合，以及遗传变异和最优变异率对选择反应的影响。为了支持迁移对表型差异的沼泽效应，我们的数据显示，在海拔梯度陡峭的地方，没有证据表明应力相关性状会发生变化，但在海拔梯度较浅的地方，则会出现显著的临床差异。然而，当检测到临床差异时，性状平均值更接近假定的局部最优的位点比性状平均值远离其局部最优的位点有更多的遗传变异。这种模式表明，基因流动也有助于对选择的持续反应。
Given that evolution can generate rapid and dramatic shifts in the ecological tolerance of a species, what prevents populations adapting to expand into new habitat at the edge of their distributions? Recent population genetic models have focused on the relative costs and benefits of migration between populations. On the one hand, migration may limit adaptive divergence by preventing local populations from matching their local selective optima. On the other hand, migration may also contribute to the genetic variance necessary to allow populations to track these changing optima. Empirical evidence for these contrasting effects of gene flow in natural situations are lacking, largely because it remains difficult to acquire. Here, we develop a way to explore theoretical models by estimating genetic divergence in traits that confer stress resistance along similar ecological gradients in rainforest Drosophila. This approach allows testing for the coupling of clinal divergence with local density, and the effects of genetic variance and the rate of change of the optimum on the response to selection. In support of a swamping effect of migration on phenotypic divergence, our data show no evidence for a cline in stress-related traits where the altitudinal gradient is steep, but significant clinal divergence where it is shallow. However, where clinal divergence is detected, sites showing trait means closer to the presumed local optimum have more genetic variation than sites with trait means distant from their local optimum. This pattern suggests that gene flow also aids a sustained response to selection.