Data from: Consequences of sibling rivalry vary across life in a passerine bird

Many studies have assessed the costs of sibling rivalry in systems where offspring always have competitors, but conclusions about sibling rivalry in these species are restricted to interpreting the cost of changes in the relative level of competition and are often complicated by the expression of potentially costly rivalry related traits. Additionally, the majority of studies focus on early-life sibling rivalry, but the costs of competition can also affect later-life performance. We test a suite of hypothesized immediate (early-life body mass, telomere length, and survival) and delayed (adult reproductive potential and lifespan) costs of sibling rivalry for offspring of differing competitive ability in Seychelles warblers, where most offspring are raised singly and hence competitor success can be compared to a competition-free scenario. Compared to those raised alone, all competing nestlings had lower body mass and weaker competitors experienced reduced survival. However, the stronger competitors appeared to have longer adult breeding tenures and lifespan than those raised alone. We propose that comparisons with competition-free groups, as well as detailed fitness measures across entire lifetimes, are needed to understand the evolution of sibling rivalry and thus individual reproductive strategy in wild systems.

已有多项研究针对子代始终存在竞争者的系统中，同胞竞争（sibling rivalry）的代价展开评估，但针对这类物种的同胞竞争相关结论，仅能局限于解读竞争相对水平变化所带来的代价，且常因潜在高代价的竞争相关性状的表达而变得复杂。
此外，绝大多数现有研究仅关注生命早期的同胞竞争，但竞争带来的代价同样会影响个体生命后期的表现。
我们针对塞舌尔莺（Seychelles warbler）不同竞争能力的子代，检验了同胞竞争所带来的一系列假说性即时代价与延迟代价：其中即时代价包括生命早期的体重、端粒长度与存活率，延迟代价则涵盖成年繁殖潜能与寿命。该物种绝大多数子代均以单只形式被抚育，因此可将存在同胞竞争的子代的表现与无竞争情境下的个体进行对比。
与单独抚育的子代相比，所有经历同胞竞争的雏鸟体重均更低，竞争能力较弱的雏鸟存活率显著下降。然而，竞争能力较强的雏鸟，其成年后的繁殖任期与寿命反而长于单独抚育的个体。
我们提出，若要阐明野生种群中同胞竞争的演化规律及个体繁殖策略，需同时开展无竞争组对照实验，并对个体终生的适合度进行精细化测量。