Data from: Genetics of decayed sexual traits in a parasitoid wasp with endosymbiont-induced asexuality

Trait decay may occur when selective pressures shift, owing to changes in environment or life style, rendering formerly adaptive traits non-functional or even maladaptive. It remains largely unknown if such decay would stem from multiple mutations with small effects or rather involve few loci with major phenotypic effects. Here, we investigate the decay of female sexual traits, and the genetic causes thereof, in a transition from haplodiploid sexual reproduction to endosymbiont-induced asexual reproduction in the parasitoid wasp Asobara japonica. We take advantage of the fact that asexual females cured of their endosymbionts produce sons instead of daughters, and that these sons can be crossed with sexual females. By combining behavioral experiments with crosses designed to introgress alleles from the asexual into the sexual genome, we found that sexual attractiveness, mating, egg fertilization and plastic adjustment of offspring sex ratio (in response to variation in local mate competition) are decayed in asexual A. japonica females. Furthermore, introgression experiments revealed that the propensity for cured asexual females to produce only sons (because of decayed sexual attractiveness, mating behavior and/or egg fertilization) is likely caused by recessive genetic effects at a single locus. Recessive effects were also found to cause decay of plastic sex-ratio adjustment under variable levels of local mate competition. Our results suggest that few recessive mutations drive decay of female sexual traits, at least in asexual species deriving from haplodiploid sexual ancestors.当环境或生活方式改变导致选择压力发生偏移时，可能出现性状退化：原本具有适应性的性状会因此丧失功能，甚至变为适应不良。目前学界仍不清楚这类性状退化究竟是由多个效应微弱的突变引发，还是仅涉及少数具有显著表型效应的基因座。 本研究以寄生蜂日本索氏茧蜂（Asobara japonica）为研究对象，探究其从单倍二倍体有性生殖向内共生体诱导的无性生殖转变过程中，雌性有性性状的退化及其遗传成因。 我们利用了两个关键实验特性：其一，清除内共生体的无性雌性会产下雄性后代而非雌性后代；其二，这些雄性可与有性雌性进行杂交。 通过将行为实验与旨在将无性种群等位基因渐渗至有性基因组的杂交实验相结合，我们发现无性型日本索氏茧蜂的雌性在性吸引力、交配行为、卵子受精以及针对局部配偶竞争（local mate competition）变化的子代性比塑性调控这几方面均出现了性状退化。 此外，基因渐渗实验还揭示，清除内共生体后的无性雌性仅能产下雄性后代——这一现象源于性吸引力、交配行为和/或卵子受精的退化——其背后大概率由单个基因座上的隐性遗传效应所致。同时，研究还发现隐性遗传效应同样会导致不同局部配偶竞争水平下的塑性性比调控能力出现退化。 本研究结果表明，至少在源自单倍二倍体有性祖先的无性物种中，雌性有性性状的退化是由少数隐性突变驱动的。