Data from: Telomere length reveals cumulative individual and transgenerational inbreeding effects in a passerine bird

Inbreeding results in more homozygous offspring that should suffer reduced fitness, but it can be difficult to quantify these costs for several reasons. First, inbreeding depression may vary with ecological or physiological stress and only be detectable over long time periods. Second, parental homozygosity may indirectly affect offspring fitness, thus confounding analyses that consider offspring homozygosity alone. Finally, measurement of inbreeding coefficients, survival and reproductive success may often be too crude to detect inbreeding costs in wild populations. Telomere length provides a more precise measure of somatic costs, predicts survival in many species and should reflect differences in somatic condition that result from varying ability to cope with environmental stressors. We studied relative telomere length in a wild population of Seychelles warblers (Acrocephalus sechellensis) to assess the lifelong relationship between individual homozygosity, which reflects genome-wide inbreeding in this species, and telomere length. In juveniles, individual homozygosity was negatively associated with telomere length in poor seasons. In adults, individual homozygosity was consistently negatively related to telomere length, suggesting the accumulation of inbreeding depression during life. Maternal homozygosity also negatively predicted offspring telomere length. Our results show that somatic inbreeding costs are environmentally dependent at certain life stages but may accumulate throughout life.

近交（inbreeding）可产生更多纯合子（homozygous）后代，此类后代的适合度（fitness）理应降低，但受诸多因素限制，量化近交带来的代价往往颇具挑战。其一，近交衰退（inbreeding depression）可能随生态或生理胁迫（ecological or physiological stress）发生动态变化，且仅能在较长时间尺度上被检测到；其二，亲本纯合度可间接影响后代适合度，这会干扰仅以后代纯合度为指标的分析；其三，近交系数（inbreeding coefficients）、存活与繁殖成功率（survival and reproductive success）的常规测量往往过于粗糙，难以在野生种群（wild populations）中检测到近交相关的适合度代价。端粒长度（Telomere length）能够更为精准地反映体细胞代价（somatic costs），可预测多个物种的存活情况，且可体现因应对环境胁迫能力差异而产生的体细胞状态差异。本研究以野生塞舌尔莺（Seychelles warblers，学名Acrocephalus sechellensis）种群为研究对象，通过检测其相对端粒长度，剖析个体纯合度——该指标可反映本物种的全基因组近交（genome-wide inbreeding）水平——与端粒长度之间的终生关联。在环境条件较差的季节，幼体（juveniles）的个体纯合度与端粒长度呈负相关；而成体（adults）的个体纯合度则始终与端粒长度呈负相关，提示近交衰退会在个体生命周期中不断累积。此外，母本纯合度（maternal homozygosity）也可负向预测后代的端粒长度。本研究结果显示，体细胞近交代价在特定生命阶段受环境调控，但可能会伴随个体终生持续累积。