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）会产生纯合度更高的后代，这类后代的适合度理应降低，但量化此类近交衰退成本往往存在多重挑战。其一，近交衰退（inbreeding depression）会随生态或生理胁迫发生动态变化，且仅能在较长时间尺度上被检测到；其二，亲本纯合度可能间接影响后代适合度，这会使仅以后代纯合度为分析指标的研究产生混杂偏倚；其三，对近交系数、存活率及繁殖成功率的测量往往过于粗略，难以在野生种群中检测到近交衰退成本。端粒长度（telomere length）可更为精准地反映体细胞成本，在诸多物种中能够预测个体存活率，且可体现因应对环境胁迫能力差异而引发的躯体状态差异。本研究以塞舌尔莺（Seychelles warbler，学名*Acrocephalus sechellensis*）的野生种群为研究对象，通过测定其相对端粒长度，探究该物种中反映全基因组近交水平的个体纯合度与端粒长度之间的终身关联。在繁殖条件较差的年份，幼鸟的个体纯合度与端粒长度呈负相关关系；成年个体的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一生中持续累积。此外，母本纯合度同样对后代端粒长度具有负向预测作用。本研究结果表明，体细胞层面的近交成本在特定生命阶段会受环境条件调控，但整体上会伴随个体终身不断累积。