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影响，是诸多生物学分支领域的重要研究议题。在鸟类中，胚胎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，由此形成从优渥（首孵雏鸟）到严苛（末孵雏鸟）的梯度环境条件。本研究以金丝雀（Serinus canaria）为研究对象，比较了孵化顺序对近交（亲本为全同胞兄妹）与远交（亲本无亲缘关系）雏鸟生长速率的影响。研究结果显示，环境胁迫程度越高，近交衰退越显著，且该效应在末孵雏鸟中表现最为突出。因此，若要全面理解近交衰退与孵化异步性的生物学意义，必须充分考量近交-环境互作效应。鉴于孵化异步性在众多鸟类中广泛存在，这一研究议题的重要性尤为凸显。目前，观测到的近交-环境互作的确切机制尚不清楚，但其可能与母体随产卵位置变化而降低的卵内营养投入（即孵化前环境），或是雏鸟在同胞竞争中的表现与/或对食物匮乏的耐受能力（即孵化后环境）相关。