Reproductive allochrony in seasonally sympatric populations maintained by differential response to photoperiod: implications for population divergence and response to climate change

Reproductive allochrony presents a potential barrier to gene flow and is common in seasonally sympatric migratory and sedentary birds. Mechanisms mediating reproductive allochrony can influence population divergence and the capacity of populations to respond to environmental change. We asked whether reproductive allochrony in seasonally sympatric birds results from a difference in response to supplementary or photoperiodic cues and whether the response varies in relation to the distance separating breeding and wintering locations as measured by stable isotopes. We held seasonally sympatric migratory and sedentary male dark-eyed juncos (Junco hyemalis) in a common garden in early spring under simulated natural changes in photoperiod and made measurements of reproductive and migratory physiology. On the same dates and photoperiods, sedentary juncos had higher testosterone (initial and gonadotropin-releasing hormone induced), more developed cloacal protuberances, and larger testes than mig...生殖异时性（reproductive allochrony）是一种潜在的基因流（gene flow）障碍，在季节性同域分布的迁徙与定居鸟类中较为普遍。介导生殖异时性的调控机制可影响种群分化进程以及种群响应环境变化的能力。本研究旨在探讨：季节性同域分布鸟类的生殖异时性是否源于对补充线索或光周期线索（photoperiodic cues）的响应差异，且该响应是否与通过稳定同位素（stable isotopes）测定的繁殖地与越冬地之间的距离存在关联。我们将季节性同域分布的迁徙性与定居性雄性暗眼灯草鹀（Junco hyemalis）置于共同花园（common garden）实验环境中，在早春时节模拟自然光周期变化，并对其生殖与迁徙生理指标开展测定。在相同日期与光周期条件下，定居型灯草鹀的睾酮（testosterone，初始水平及促性腺激素释放激素（gonadotropin-releasing hormone）诱导水平）、泄殖腔突起（cloacal protuberances）发育程度以及睾丸尺寸均显著高于迁徙型……