Data from: Hatching asynchrony aggravates inbreeding depression in a songbird (Serinus canaria): an inbreeding-environment interaction

Understanding how the intensity of inbreeding depression is influenced by stressful environmental conditions is an important area of enquiry in various fields of biology. In birds, environmental stress during early development is often related to hatching asynchrony; differences in age, and thus size, impose a gradient in conditions ranging from benign (first hatched chick) to harsh (last hatched chick). Here, we compared the effect of hatching order on growth rate in inbred (parents are full siblings) and outbred (parents are unrelated) canary chicks (Serinus canaria). We found that inbreeding depression was more severe under more stressful conditions, being most evident in later hatched chicks. Thus, consideration of inbreeding-environment interactions is of vital importance for our understanding of the biological significance of inbreeding depression and hatching asynchrony. The latter is particularly relevant given that hatching asynchrony is a widespread phenomenon, occurring in many bird species. The exact causes of the observed inbreeding-environment interaction are as yet unknown, but may be related to a decrease in maternal investment in egg contents with laying position (i.e. pre-hatching environment), or to performance of the chicks during sibling competition and/or their resilience to food shortage (i.e. post-hatching environment).

探究近交衰退（inbreeding depression）的强度如何受胁迫环境条件调控，是诸多生物学分支领域的重要研究议题。在鸟类类群中，个体早期发育阶段所经历的环境胁迫常与孵化异步性（hatching asynchrony）相关；雏鸟间的日龄乃至体型差异，会形成梯度化的生存环境：从条件较为优越的首孵雏鸟，到生存压力严苛的末孵雏鸟。本研究针对近交（亲本为全同胞个体）与远交（亲本无亲缘关系）的金丝雀（Serinus canaria）雏鸟，比较了孵化顺序对其生长速率的影响。研究结果显示，在胁迫程度更高的环境条件下，近交衰退现象更为显著，且该效应在末孵雏鸟中表现得最为突出。由此可见，对近交-环境交互作用的考量，对于阐明近交衰退与孵化异步性的生物学意义至关重要。鉴于孵化异步性在众多鸟类物种中广泛分布，这一研究视角尤为关键。目前，观测到的近交-环境交互作用的确切成因尚不明确，其可能与母体随产卵位置变化对卵内容物的投资降低（即孵化前环境）相关，亦可能与雏鸟在同胞竞争中的表现和/或对食物匮乏的耐受能力（即孵化后环境）有关。