Estimating the impact of divergent mating phenology between residents and migrants on the potential for gene flow
Estimating the impact of divergent mating phenology between residents and migrants on the potential for gene flow
复制标题
估计居民和移民之间不同的交配物候对基因流动潜力的影响
作者：
Colin Bonner;N. Sokolov;Sally Erin Westover;M. Ho;A. E. Weis
摘要 种群之间的基因流动可以使有益等位基因和遗传多样性在种群之间传播，这对于保护、入侵生物学和农业具有重要意义。种群之间的基因流动水平不仅随着距离的不同而变化，而且还随着生殖物候的差异而变化。由于物候通常是适应当地情况的，到达的移民可能在繁殖上与居民不同步，这可能会抑制已实现的基因流动。在开花植物中，物候差异对种群间杂交的潜在影响可以通过常住种群和迁徙种群之间开花时间表（能够进行花粉交换的每日花朵数量）的重叠来预测。这种基于亲本表型的前瞻性杂交估计的准确性取决于驻留花和迁徙活跃花之间无偏花粉转移的假设。我们在模拟单个大基因流事件的实验中测试了物候差异对居民-迁徙交配频率的影响。我们首先前瞻性地估计了两个油菜系或早花和晚花的交配频率。然后，我们通过后代测试回顾性地估计了已实现的交配频率。这两种估计在温室实验中非常一致，实验程序确保了饱和、公正的授粉。尽管前瞻性和回顾性估计是相关的，但在田间自然授粉下，驻地-迁徙交配率低于仅通过物候差异估计的值。在这两个实验中，居民和移民之间在开花时间表形状上的差异导致了不对称杂交。结果表明，基于交配时间表的杂交前瞻性估计可能是评估潜在基因流的有用工具，尽管并不完美。它们还说明了交配物候对生殖隔离的程度和对称性的影响。
Abstract Gene flow between populations can allow the spread of beneficial alleles and genetic diversity between populations, with importance to conservation, invasion biology, and agriculture. Levels of gene flow between populations vary not only with distance, but also with divergence in reproductive phenology. Since phenology is often locally adapted, arriving migrants may be reproductively out of synch with residents, which can depress realized gene flow. In flowering plants, the potential impact of phenological divergence on hybridization between populations can be predicted from overlap in flowering schedules—the daily count of flowers capable of pollen exchange—between a resident and migrant population. The accuracy of this prospective hybridization estimate, based on parental phenotypes, rests upon the assumptions of unbiased pollen transfer between resident and migrant active flowers. We tested the impact of phenological divergence on resident–migrant mating frequencies in experiments that mimicked a single large gene flow event. We first prospectively estimated mating frequencies two lines of Brassica rapaselected or early and late flowering. We then estimated realized mating frequencies retrospectively through progeny testing. The two estimates strongly agreed in a greenhouse experiment, where procedures ensured saturating, unbiased pollination. Under natural pollination in the field, the rate of resident–migrant mating, was lower than estimated by phenological divergence alone, although prospective and retrospective estimates were correlated. In both experiments, differences between residents and migrants in flowering schedule shape led to asymmetric hybridization. Results suggest that a prospective estimate of hybridization based on mating schedules can be a useful, although imperfect, tool for evaluating potential gene flow. They also illustrate the impact of mating phenology on the magnitude and symmetry of reproductive isolation.