Hall Megan C, Willis John H
Department of Genetics, Box 7614, North Carolina State University, Raleigh, North Corolina 27695, USA.
Evolution. 2006 Dec;60(12):2466-77.
The timing of when to initiate reproduction is an important transition in any organism's life cycle. There is much variation in flowering time among populations, but we do not know to what degree this variation contributes to local adaptation. Here we use a reciprocal transplant experiment to examine the presence of divergent natural selection for flowering time and local adaptation between two distinct populations of Mimulus guttatus. We plant both parents and hybrids (to tease apart differences in suites of associated parental traits) between these two populations into each of the two native environments and measure floral, vegetative, life-history, and fitness characters to assess which traits are under selection at each site. Analysis of fitness components indicates that each of these plant populations is locally adapted. We obtain striking evidence for divergent natural selection on date of first flower production at these two sites. Early flowering is favored at the montane site, which is inhabited by annual plants and characterized by dry soils in midsummer, whereas intermediate (though later) flowering dates are selectively favored at the temperate coastal site, which is inhabited by perennial plants and is almost continually moist. Divergent selection on flowering time contributes to local adaptation between these two populations of M. guttatus, suggesting that genetic differentiation in the timing of reproduction may also serve as a partial reproductive isolating barrier to gene flow among populations.
何时开始繁殖的时机是任何生物体生命周期中的一个重要转变。不同种群之间的开花时间存在很大差异，但我们并不清楚这种差异在多大程度上有助于局部适应。在这里，我们进行了一项 reciprocal transplant 实验，以研究在两个不同的黄花沟酸浆种群之间，开花时间是否存在趋异自然选择以及局部适应情况。我们将这两个种群的亲本和杂种（以区分相关亲本性状组合的差异）种植到两个原生环境中的每一个，并测量花部、营养、生活史和适合度特征，以评估每个地点哪些性状受到选择。适合度成分分析表明，这些植物种群中的每一个都实现了局部适应。我们获得了显著证据，表明在这两个地点，首次开花日期存在趋异自然选择。在山地地点，早期开花受到青睐，该地点生长着一年生植物，其特征是仲夏时节土壤干燥；而在温带沿海地点，中间（尽管较晚）开花日期受到选择性青睐，该地点生长着多年生植物，几乎持续湿润。开花时间的趋异选择有助于这两个黄花沟酸浆种群之间的局部适应，这表明繁殖时间的遗传分化也可能部分地作为种群间基因流动的生殖隔离屏障。
