Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland.
J Evol Biol. 2010 Nov;23(11):2333-45. doi: 10.1111/j.1420-9101.2010.02094.x. Epub 2010 Sep 6.
Inbreeding adversely affects life history traits as well as various other fitness-related traits, but its effect on cognitive traits remains largely unexplored, despite their importance to fitness of many animals under natural conditions. We studied the effects of inbreeding on aversive learning (avoidance of an odour previously associated with mechanical shock) in multiple inbred lines of Drosophila melanogaster derived from a natural population through up to 12 generations of sib mating. Whereas the strongly inbred lines after 12 generations of inbreeding (0.75<F<0.93) consistently showed reduced egg-to-adult viability (on average by 28%), the reduction in learning performance varied among assays (average=18% reduction), being most pronounced for intermediate conditioning intensity. Furthermore, moderately inbred lines (F=0.38) showed no detectable decline in learning performance, but still had reduced egg-to-adult viability, which indicates that overall inbreeding effects on learning are mild. Learning performance varied among strongly inbred lines, indicating the presence of segregating variance for learning in the base population. However, the learning performance of some inbred lines matched that of outbred flies, supporting the dominance rather than the overdominance model of inbreeding depression for this trait. Across the inbred lines, learning performance was positively correlated with the egg-to-adult viability. This positive genetic correlation contradicts a trade-off observed in previous selection experiments and suggests that much of the genetic variation for learning is owing to pleiotropic effects of genes affecting functions related to survival. These results suggest that genetic variation that affects learning specifically (rather than pleiotropically through general physiological condition) is either low or mostly due to alleles with additive (semi-dominant) effects.
近亲繁殖会对生活史特征以及各种其他与适应度相关的特征产生不利影响，但尽管其对许多动物在自然条件下的适应度很重要，但其对认知特征的影响在很大程度上仍未得到探索。我们研究了近亲繁殖对厌恶学习（避免与机械冲击相关的气味）的影响，使用了来自自然种群的多个近交系果蝇，通过最多 12 代的兄妹交配来进行繁殖。尽管在经过 12 代近亲繁殖后（0.75<F<0.93），强烈近交系的卵到成虫的存活率（平均降低 28%）持续下降，但学习表现的下降在不同的测试中存在差异（平均降低 18%），在中等条件强度下最为明显。此外，中度近交系（F=0.38）的学习表现没有明显下降，但卵到成虫的存活率仍然降低，这表明总体上近亲繁殖对学习的影响是轻微的。学习表现因强烈近交系而异，表明基础种群中存在学习的分离方差。然而，一些近交系的学习表现与非近亲繁殖的果蝇相匹配，支持了该特征的近交衰退是显性而不是超显性的模型。在整个近交系中，学习表现与卵到成虫的存活率呈正相关。这种正向遗传相关性与之前的选择实验中观察到的权衡相悖，表明学习的大部分遗传变异是由于与生存相关的功能的基因的多效性造成的。这些结果表明，专门影响学习的遗传变异（而不是通过一般生理状况的多效性）要么很低，要么主要归因于具有加性（半显性）效应的等位基因。
