Department of Biology, University of California, Riverside, CA 92507, USA.
Proc Biol Sci. 2012 Sep 22;279(1743):3756-64. doi: 10.1098/rspb.2012.1018. Epub 2012 Jun 20.
Recent meta-analyses conducted across a broad range of taxa have demonstrated a strong linear relationship between the change in magnitude of inbreeding depression under stress and stress level, measured as fitness loss in outbred individuals. This suggests that a general underlying response may link stress and inbreeding depression. However, this relationship is based primarily on laboratory data, and it is unknown whether natural environments with multiple stressors and fluctuating stress levels alter how stress affects inbreeding depression. To test whether the same pattern persists in the field, we investigated the effect of seasonal variation on stress level and inbreeding depression in a 3-year field study measuring the productivity of captive populations of inbred and outbred Drosophila melanogaster. We found cold winter temperatures were most stressful and induced the greatest inbreeding depression. Furthermore, these data, collected under natural field conditions, conformed to the same predictive linear relationship seen in Drosophila laboratory studies, with inbreeding depression increasing by 0.17 lethal equivalents for every 10 per cent increase in stress level. Our results suggest that under natural conditions stress level is a primary determinant of the magnitude of inbreeding depression and should be considered when assessing extinction vulnerability in small populations.
最近在广泛的分类群中进行的荟萃分析表明，在压力下近亲繁殖衰退的幅度变化与压力水平之间存在很强的线性关系，压力水平以异交个体的适应度损失来衡量。这表明，一种普遍的潜在反应可能将压力和近亲繁殖衰退联系起来。然而，这种关系主要基于实验室数据，尚不清楚具有多种胁迫源和波动胁迫水平的自然环境是否会改变胁迫对近亲繁殖衰退的影响。为了测试这种模式是否在野外仍然存在，我们在一项为期 3 年的野外研究中调查了季节性变化对胁迫水平和近交衰退的影响，该研究测量了人工饲养的近交和远交黑腹果蝇种群的生产力。我们发现，寒冷的冬季温度最具压力，并导致最大的近亲繁殖衰退。此外，这些在自然野外条件下收集的数据符合在果蝇实验室研究中看到的相同预测线性关系，即随着胁迫水平每增加 10%，近亲繁殖衰退增加 0.17 个致死当量。我们的研究结果表明，在自然条件下，胁迫水平是近亲繁殖衰退幅度的主要决定因素，在评估小种群的灭绝脆弱性时应予以考虑。
