Behaviour and Genetics of Social Insects Laboratory, School of Biological Sciences A12, University of Sydney, NSW, 2006, Australia.
Evolution. 2014 Jan;68(1):125-36. doi: 10.1111/evo.12231. Epub 2013 Sep 2.
Correlations between fitness and genome-wide heterozygosity (heterozygosity-fitness correlations, HFCs) have been reported across a wide range of taxa. The genetic basis of these correlations is controversial: do they arise from genome-wide inbreeding ("general effects") or the "local effects" of overdominant loci acting in linkage disequilibrium with neutral loci? In an asexual thelytokous lineage of the Cape honey bee (Apis mellifera capensis), the effects of inbreeding have been homogenized across the population, making this an ideal system in which to detect overdominant loci, and to make inferences about the importance of overdominance on HFCs in general. Here we investigate the pattern of zygosity along two chromosomes in 42 workers from the clonal Cape honey bee population. On chromosome III (which contains the sex-locus, a gene that is homozygous-lethal) and chromosome IV we show that the pattern of zygosity is characterized by loss of heterozygosity in short regions followed by the telomeric restoration of heterozygosity. We infer that at least four selectively overdominant genes maintain heterozygosity on chromosome III and three on chromosome IV via local effects acting on neutral markers in linkage disequilibrium. We conclude that heterozygote advantage and local effects may be more common and evolutionarily significant than is generally appreciated.
在广泛的分类群中，已经报道了适合度与全基因组杂合度（杂合度-适合度相关性，HFCs）之间的相关性。这些相关性的遗传基础存在争议：它们是由全基因组近交（“一般效应”）引起的，还是与中性位点处于连锁不平衡的超显性位点的“局部效应”引起的？在开普蜜蜂（Apis mellifera capensis）的无性雌性生殖系中，近交的影响在整个种群中已经同质化，这使得该系统成为检测超显性位点的理想系统，并可以对超显性在 HFC 中的重要性做出推断。在这里，我们研究了来自克隆开普蜜蜂种群的 42 只工蜂的两条染色体上的基因型频率模式。在染色体 III（包含性染色体，一个纯合致死的基因）和染色体 IV 上，我们表明基因型频率模式的特征是短区域内杂合性丧失，然后是端粒处杂合性恢复。我们推断，至少有四个选择性超显性基因通过与中性标记处于连锁不平衡的局部效应，在染色体 III 上维持杂合性，在染色体 IV 上维持三个。我们得出结论，杂合优势和局部效应可能比普遍认为的更为常见和具有进化意义。
