Data from: No evidence for strong cytonuclear conflict over sex allocation in a simultaneously hermaphroditic flatworm

Background: Cytoplasmic sex allocation distorters, which arise from cytonuclear conflict over the optimal investment into male versus female reproductive function, are some of the best-researched examples for genomic conflict. Among hermaphrodites, many such distorters have been found in plants, while, to our knowledge, none have been clearly documented in animals. Methods: Here we provide a quantitative test for cytonuclear conflict over sex allocation in the simultaneously hermaphroditic flatworm Macrostomum lignano. We used a quantitative genetic breeding design, employing pair-wise crosses of 2 × 15 independent inbred lines, to partition the phenotypic variance in several traits (including sex allocation) into its nuclear and cytoplasmic components. Results: Although the nuclear genetic background had a significant effect on all traits analyzed, we found significant cytoplasmic genetic variation only for ovary size, there explaining just 4.1% of the variance. A subsequent statistical power analysis showed that the experimental design had considerable power to detect cytonuclear interactions. Conclusion: We conclude that there were no strong effects of cytonuclear conflict in the studied populations, possibly because the usually compact mitochondrial genomes in animals have a lower evolvability than the large mitochondrial genomes in plants or because the sampled populations currently do not harbor variation at putative distorter and/or the restorer loci.

研究背景：胞质性别分配畸变因子（cytoplasmic sex allocation distorters）由核质冲突引发，该冲突围绕雄性与雌性生殖功能的最优资源投入展开，是目前研究最为深入的基因组冲突案例之一。在雌雄同体生物中，这类畸变因子已在植物中被大量发现，但据我们所知，在动物中尚无明确的记录。

研究方法：本研究针对同时雌雄同体的扁形动物Macrostomum lignano开展了一项关于性别分配相关核质冲突的定量检验。我们采用定量遗传育种设计，通过2组各15个独立自交系的成对杂交，将包括性别分配在内的多个性状的表型方差分解为核遗传组分与胞质遗传组分。

研究结果：尽管核遗传背景对所有分析性状均具有显著影响，但我们仅在卵巢大小这一性状中检测到了显著的胞质遗传变异，其解释的表型方差仅为4.1%。后续的统计功效分析显示，本实验设计具备检测核质互作的较强能力。

研究结论：我们推断，在所研究的种群中，核质冲突并未产生显著效应。这一现象可能源于两点：其一，动物通常较为紧凑的线粒体基因组，其演化能力低于植物中较大的线粒体基因组；其二，所采样的种群目前尚未在假定的畸变因子位点及/或恢复位点携带可供检测的遗传变异。