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).探究近亲衰退（inbreeding depression）的强度如何受胁迫环境条件的影响，是诸多生物学领域的重要研究方向。在鸟类中，早期发育阶段的环境胁迫往往与孵化异步性（hatching asynchrony）相关；雏鸟间的年龄差异进而导致体型差异，由此形成了从宽松（最先孵化的雏鸟）到严苛（最后孵化的雏鸟）的环境梯度。本研究以金丝雀（Serinus canaria）雏鸟为对象，比较了近交组（亲本为全同胞兄妹，full siblings）与远交组（亲本无亲缘关系）个体的孵化顺序对其生长速率的影响。研究结果显示，在更为严苛的环境条件下，近亲衰退的程度更为显著，该效应在后期孵化的雏鸟中表现最为明显。因此，厘清近亲衰退与环境的交互作用，对于我们理解近亲衰退和孵化异步性的生物学意义至关重要。鉴于孵化异步性在诸多鸟类中广泛存在，对该现象的相关研究尤其具有重要价值。目前尚未明确观测到的近亲衰退-环境交互作用的确切成因，但其可能与母体随产卵位置变化对卵内营养物质的投入减少（即孵化前环境）相关，或是与雏鸟在同胞竞争中的表现及/或其对食物短缺的耐受能力（即孵化后环境）有关。