Recessive Z-linked lethals and the retention of haplotype diversity in a captive butterfly population.
Recessive Z-linked lethals and the retention of haplotype diversity in a captive butterfly population.
复制标题
圈养蝴蝶种群中隐性 Z 连锁致死和单倍型多样性的保留。
DOI：
10.1038/s41437-020-0316-x
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发表时间：
2020
期刊：
影响因子：
3.8
通讯作者：
Saccheri IJ
中科院分区：
文献类型：
--
作者：
Saccheri IJ
性染色体被预测为具有升高的性拮抗变异水平，这是由于同配子与异配子性别中隐性性状的遗传率不对称。这种进化动态可能表现为高隐性负荷，特别是影响同配性别，并保留单倍型多样性在小种群。我们测试的假设，Z染色体在butterflyBicyclus anynanacarries高近交负荷的男性生育力和活力。纯合性的Z染色体块产生的女儿父亲回交，并推断通过连锁图定位的标记位点。雄性不育，在一般情况下，无关的Z的任何地区的纯合性，但有一个极端赤字的纯合男性在2厘米的间隔在所有的家庭。相反，在他们的（半合子）姐妹篇中没有检测到相应的Z基因型偏斜。在历史上的近交系中观察到相同的模式，表明在祖先群体中隐性致死的频率很高。1993年至2006年（在Ne ~ 160的70代）之间的等位基因频率变化表明，尽管失去了许多单倍型，多样性仍保持显着高于中性预期。在致死区域的有效超显性可以解释这种局部效应，但在染色体的其他部分不能解释这种效应，这些部分也与持续的连锁不平衡有关。这些意想不到的模式表明其他因素的作用，例如上位选择、重组抑制、选型交配和减数分裂驱动。我们的研究结果强调了平衡选择在维持近交系负荷和连锁遗传多样性方面的作用。
Sex chromosomes are predicted to harbour elevated levels of sexually antagonistic variation due to asymmetries in the heritability of recessive traits in the homogametic versus heterogametic sex. This evolutionary dynamic may manifest as high recessive load specifically affecting the homogametic sex, and the retention of haplotype diversity in small populations. We tested the hypothesis that the Z chromosome in the butterflyBicyclus anynanacarries a high inbred load for male fertility and viability. Homozygosity of Z chromosome blocks was produced by daughter–father backcrosses, and inferred from marker loci positioned via a linkage map. Male sterility was, in general, unrelated to homozygosity in any region of the Z, but there was an extreme deficit of homozygous males within a 2 cM interval in all families. In contrast, no corresponding skew in Z genotype was detected in their (hemizygous) sisters. The same pattern was observed in historically inbred lines, indicating a high frequency of recessive lethals in the ancestral population. Allele-frequency changes between 1993 and 2006 (70 generations atNe~ 160) show that, despite the loss of many haplotypes, diversity was retained significantly above the neutral expectation. Effective overdominance in the lethal region can account for this effect locally but not in other parts of the chromosome, that are also associated with persistent linkage disequilibrium. These unexpected patterns suggest the operation of other factors, such as epistatic selection, recombination suppression, assortative mating and meiotic drive. Our results highlight the role of balancing selection in maintaining the inbred load and linked genetic diversity.