Centre for Evolutionary Biology, School of Animal Biology (M092), The University of Western Australia, Crawley, WA 6009, Australia.
BMC Evol Biol. 2014 Mar 17;14:51. doi: 10.1186/1471-2148-14-51.
One proposed consequence of inbreeding is a skewed sex ratio arising from sex specific mortality in the homogametic sex caused by inbreeding on the sex chromosome. However, recent work suggests that random distortions in sex ratio due to autosomal inbreeding may be of greater importance. In this study, we investigate the effect of biologically realistic levels of inbreeding on sex ratio and sex specific mortality in Drosophila melanogaster. We use two pedigree crossing designs to either maximise or minimise inbreeding on the X-chromosome whilst producing identical autosomal inbreeding.
We found increased female mortality and male biased sex ratios associated with inbreeding in our high, but not low, X-inbreeding pedigree. While our results are more consistent with being driven by inbreeding on the X-chromosome than on the autosomes, the marked difference between treatments does not fit closely the expectations of either model.
Our results are only partly consistent with the hypothesis that inbreeding on the X-chromosome can cause greater fitness reductions in the homogametic sex. Whilst the results of our study are not conclusive, they suggest that directional distortions in sex ratio due to inbreeding can occur, and highlight the need for further investigation on this topic.
近亲繁殖的一个可能后果是由于性染色体上的近亲繁殖导致同型配子性别中特定性别的死亡率增加，从而导致性别比例偏斜。然而，最近的研究表明，由于常染色体近亲繁殖导致的随机性别比例扭曲可能更为重要。在这项研究中，我们研究了在果蝇中，生物上合理的近亲繁殖水平对性别比例和性别特异性死亡率的影响。我们使用两种系谱交叉设计，要么最大限度地增加 X 染色体上的近亲繁殖，要么最大限度地减少 X 染色体上的近亲繁殖，同时产生相同的常染色体近亲繁殖。
我们发现，在高 X 染色体近亲繁殖系谱中，与近亲繁殖相关的雌性死亡率增加和雄性偏性性别比例增加，但在低 X 染色体近亲繁殖系谱中则没有。虽然我们的结果更符合 X 染色体而非常染色体上的近亲繁殖导致的情况，但处理之间的显著差异并不符合任何一种模型的预期。
我们的结果仅部分符合 X 染色体上的近亲繁殖会导致同型配子性别中更大的适应度降低的假设。虽然我们的研究结果没有定论，但它们表明，由于近亲繁殖导致的性别比例的定向扭曲可能会发生，并强调需要进一步研究这个问题。
