Fox Charles W, Scheibly Kristy L, Wallin William G, Hitchcock Lisa J, Stillwell R Craig, Smith Benjamin P
Department of Entomology, University of Kentucky, Lexington, Kentucky 40546-0091, USA.
Genetics. 2006 Oct;174(2):763-73. doi: 10.1534/genetics.106.060392. Epub 2006 Aug 3.
We examine the inbreeding load for adult life span and mortality rates of two seed beetle species, Callosobruchus maculatus and Stator limbatus. Inbreeding load differs substantially between males and females in both study populations of C. maculatus--life span of inbred females was 9-13% shorter than the life span of outbred females, whereas the life span of inbred males did not differ from the life span of outbred males. The effect of inbreeding on female life span was largely due to an increase in the slope of the mortality curve. In contrast, inbreeding had only a small effect on the life span of S. limbatus--life spans of inbred beetles were approximately 5% shorter than those of outbred beetles, and there was no difference in inbreeding load between the sexes. The inbreeding load for mean life span was approximately 0.4-0.6 lethal equivalents per haploid gamete for female C. maculatus and approximately 0.2-0.3 for both males and females of S. limbatus, all within the range of estimates commonly obtained for Drosophila. However, contrary to the predictions of mutation-accumulation models, inbreeding load for loci affecting mortality rates did not increase with age in either species, despite an effect of inbreeding on the initial rate of increase in mortality. This was because mortality rates decelerated with age and converged to a mortality plateau for both outbred and inbred beetles.
我们研究了两种豆象（Callosobruchus maculatus和Stator limbatus）成年寿命和死亡率的近亲繁殖负荷。在C. maculatus的两个研究种群中，近亲繁殖负荷在雄性和雌性之间存在显著差异——近亲繁殖雌性的寿命比非近亲繁殖雌性短9%-13%，而近亲繁殖雄性的寿命与非近亲繁殖雄性没有差异。近亲繁殖对雌性寿命的影响主要是由于死亡率曲线斜率的增加。相比之下，近亲繁殖对S. limbatus的寿命影响较小——近亲繁殖甲虫的寿命比非近亲繁殖甲虫短约5%，且两性之间的近亲繁殖负荷没有差异。雌性C. maculatus平均寿命的近亲繁殖负荷约为每个单倍体配子0.4-0.6个致死当量，S. limbatus的雄性和雌性均约为0.2-0.3个致死当量，均在通常针对果蝇获得的估计范围内。然而，与突变积累模型的预测相反，尽管近亲繁殖对死亡率的初始增加速率有影响，但在这两个物种中，影响死亡率的基因座的近亲繁殖负荷均未随年龄增加，这是因为无论是非近亲繁殖还是近亲繁殖的甲虫，死亡率都随着年龄的增长而减速并趋于一个死亡率平台期。
