School of Natural Sciences, Bangor University, Bangor LL57 2DG, UK.
Field Research Station at Fort Missoula, Division of Biological Sciences, University of Montana, Missoula, MT, USA.
Integr Comp Biol. 2023 Sep 15;63(3):742-757. doi: 10.1093/icb/icad061.
A huge amount of research attention has focused on the evolution of life histories, but most research focuses on dominant individuals that acquire a disproportionate level of reproductive success, while the life histories and reproductive tactics of subordinate individuals have received less attention. Here, we review the links between early life adversity and performance during adulthood in birds, and highlight instances in which subordinate individuals outperform dominant conspecifics. Subordinate individuals are those from broods raised under high risk of predation, with low availability of food, and/or with many parasites. Meanwhile, the broods of many species hatch or are born asynchronously and mitigation of the asynchrony is generally lacking from variation in maternal effects such as egg size and hormone deposition or genetic effects such as offspring sex or parentage. Subordinate individuals employ patterns of differential growth to attempt to mitigate the adversity they experience during early life, yet they overwhelmingly fail to overcome their initial handicap. In terms of surviving through to adulthood, subordinate individuals employ other "suboptimal" tactics, such as adaptively timing foraging behaviors to avoid dominant individuals. During adulthood, meanwhile, subordinate individuals rely on "suboptimal" tactics, such as adaptive dispersal behaviors and competing for partners at optimal times, because they represent the best options available to them to acquire copulations whenever possible. We conclude that there is a gap in knowledge for direct links between early life adversity and subordination during adulthood, meaning that further research should test for links. There are instances, however, where subordinate individuals employ "suboptimal" tactics that allow them to outperform dominant conspecifics during adulthood.
大量的研究关注于生命史的进化，但大多数研究集中在获得不成比例生殖成功的优势个体上，而处于从属地位的个体的生命史和生殖策略则受到较少关注。在这里，我们回顾了鸟类早期逆境与成年期表现之间的联系，并强调了从属个体表现优于优势同种个体的情况。从属个体是指那些在高捕食风险、食物供应不足和/或寄生虫较多的环境中长大的个体。与此同时，许多物种的雏鸟孵化或出生是不同步的，而母体效应（如卵大小和激素沉积）或遗传效应（如后代性别或亲代）中的变异性一般无法缓解这种不同步。从属个体采用不同的生长模式来试图减轻其在早期生活中所经历的逆境，但它们几乎无法克服其最初的劣势。在成年后生存方面，从属个体采用其他“次优”策略，例如适应性地调整觅食行为以避免优势个体。而在成年期，从属个体则依赖于“次优”策略，例如适应性的扩散行为和在最佳时间竞争伴侣，因为这些策略是它们在尽可能获得交配机会时可利用的最佳选择。我们得出的结论是，早期逆境与成年期从属之间的直接联系存在知识差距，这意味着应该进一步研究以测试它们之间的联系。然而，在某些情况下，从属个体采用“次优”策略，使它们在成年期表现优于优势同种个体。
