Data from: Hormonal, behavioral, and life-history traits exhibit correlated shifts in relation to population establishment in a novel environment

Climate change, habitat alteration, range expansions, and biological invasions are all predicted to require rapid shifts in multiple traits including behavior and life-history, both for initial population establishment and subsequent adaptation. Hormonal mechanisms likely play a key role in facilitating or constraining plastic and genetic responses for suites of traits, but few studies have evaluated their role in shaping contemporary adaptation or diversification. We examined multiple phenotypic adjustments and associated hormonal changes following a recent (early 1980s) colonization event, in which a temperate-breeding songbird, the Dark-eyed Junco, Junco hyemalis, became established in the Mediterranean climate of San Diego, California, USA. The milder climate has led to an extended breeding season and year-round residency, and we document shifts in multiple sexually selected behaviors and plumage traits. Testosterone titers in San Diego were elevated for longer but with a lower peak value compared to a nearby native-range population, and correlations between testosterone and related traits were similar within and among populations. A common garden study indicated that changes in testosterone likely represent plastic responses to the less seasonal environment of the city, providing the context against which subsequent genetic changes in morphology likely occurred. We argue that correlated shifts in multiple traits, organized by underlying physiology, may be a generally important element of many successful adjustments to changing environments.

气候变化、生境改变、分布范围扩张以及生物入侵等过程，均被认为会促使生物在行为、生活史等多重性状上发生快速调整，以满足初始种群建立与后续适应性演化的需求。激素调控机制可能在促进或限制多性状组合的表型可塑性与遗传响应方面发挥核心作用，但目前鲜有研究评估其在塑造当代适应与物种分化进程中所发挥的作用。本研究聚焦于一起发生于20世纪80年代初的定居事件，对其引发的多重表型调整与相关激素变化展开了系统性调查：该事件中，一种温带繁殖型鸣禽暗眼灯草鹀（Dark-eyed Junco，*Junco hyemalis*）在美国加利福尼亚州圣迭戈的地中海气候区成功定居。相较于其原生分布区，圣迭戈更为温和的气候使得该种群的繁殖季显著延长，并实现了全年居留；研究团队同时记录到其多项性选择相关行为与羽衣性状均发生了改变。与邻近的原生种群相比，圣迭戈种群的睾酮（Testosterone）滴度升高持续时间更长，但峰值更低；且睾酮与相关性状之间的相关性在种群内部与种群间均保持一致。共同花园（common garden）实验结果表明，睾酮水平的变化大概率是对城市内季节性较弱环境的表型可塑性响应，这为后续形态学相关遗传改变的发生提供了演化背景。我们认为，由内在生理机制统筹的多重性状协同转变，或许是众多生物成功适应多变环境过程中普遍存在的关键要素。