Data from: The nature of nurture in a wild mammal’s fitness

Genetic variation in fitness is required for the adaptive evolution of any trait but natural selection is thought to erode genetic variance in fitness. This paradox has motivated the search for mechanisms that might maintain a population's adaptive potential. Mothers make many contributions to the attributes of their developing offspring and these maternal effects can influence responses to natural selection if maternal effects are themselves heritable. Maternal genetic effects (MGEs) on fitness might, therefore, represent an underappreciated source of adaptive potential in wild populations. Here we used two decades of data from a pedigreed wild population of North American red squirrels to show that MGEs on offspring fitness increased the population's evolvability by over two orders of magnitude relative to expectations from direct genetic effects alone. MGEs are predicted to maintain more variation than direct genetic effects in the face of selection, but we also found evidence of maternal effect trade-offs. Mothers that raised high-fitness offspring in one environment raised low-fitness offspring in another environment. Such a fitness trade-off is expected to maintain maternal genetic variation in fitness, which provided additional capacity for adaptive evolution beyond that provided by direct genetic effects on fitness.

任何性状实现适应性进化，均依赖于适合度相关的遗传变异，但学界普遍认为自然选择会侵蚀适合度的遗传方差。这一悖论推动研究者探寻能够维持种群适应性演化潜能的机制。母体对发育中子代的性状具有多重贡献，若母体效应本身可遗传，则其可影响种群对自然选择的响应。因此，针对适合度的母体遗传效应（Maternal Genetic Effects, MGEs），或许是野生种群中未被充分重视的适应性演化潜能来源。
本研究依托一个具有完整谱系记录的北美红松鼠野生种群长达20年的监测数据，证实：针对子代适合度的母体遗传效应，可使种群可演化性较仅考虑直接遗传效应的理论预期提升两个数量级以上。理论预测显示，在选择压力下，母体遗传效应相较直接遗传效应能够维持更多的遗传变异；但本研究同时发现了母体效应权衡的相关证据：在某一环境中抚育出高适合度子代的母体，在另一环境中所抚育子代的适合度却相对较低。这类适合度权衡被认为能够维持适合度相关的母体遗传变异，从而为适应性进化提供超出直接遗传效应所能赋予的额外演化容量。