性二态是由于两性之间的适应性最佳而产生的。性别之间的表型差异可以从轻度到极端。萤火虫,生物发光甲虫,呈现不同程度的性二态,物种表现出非常温和的性二态性,提出了一个独特的框架来研究跨物种的性二态特征的进化。在这项工作中,我们提出了两个萤火虫物种的新组装基因组,Lamprohibzaplindula和Luciolaitalica,具有不同程度的性二态性的物种。我们发现在〜180Mya中X染色体的高度同位保守性,并在我们的两只萤火虫中找到完整的X染色体剂量补偿,暗示上调单个男性X染色体的共同机制。在两个身体部位发现了不同程度的性别偏倚表达基因,显示出物种之间不同比例的表达保守性。有趣的是,我们没有发现性别偏倚基因的X染色体富集,而是检索性别偏倚基因的常染色体富集。我们进一步发现性别偏向基因的内含子区域中更高的核苷酸多样性,暗示通过性选择维持杂合性。我们确定了不同水平的性别偏倚基因表达差异,包括一组显示物种之间保守的性别偏倚基因表达的基因。发散和保守的性别偏见基因是测试其在维持性二态特征中的作用的良好候选者。
Sexual dimorphism arises because of divergent fitness optima between the sexes. Phenotypic divergence between sexes can range from mild to extreme. Fireflies, bioluminescent beetles, present various degrees of sexual dimorphism, with species showing very mild sexual dimorphism to species presenting female-specific neoteny, posing a unique framework to investigate the evolution of sexually dimorphic traits across species. In this work, we present novel assembled genomes of two firefly species, Lamprohiza splendidula and Luciola italica, species with different degrees of sexual dimorphism. We uncover high synteny conservation of the X-chromosome across ~ 180 Mya and find full X-chromosome dosage compensation in our two fireflies, hinting at common mechanism upregulating the single male X-chromosome. Different degrees of sex-biased expressed genes were found across two body parts showing different proportions of expression conservation between species. Interestingly, we do not find X-chromosome enrichment of sex-biased genes, but retrieve autosomal enrichment of sex-biased genes. We further uncover higher nucleotide diversity in the intronic regions of sex-biased genes, hinting at a maintenance of heterozygosity through sexual selection. We identify different levels of sex-biased gene expression divergence including a set of genes showing conserved sex-biased gene expression between species. Divergent and conserved sex-biased genes are good candidates to test their role in the maintenance of sexually dimorphic traits.