Data from: Haploid selection within a single ejaculate increases offspring fitness

An inescapable consequence of sex in eukaryotes is the evolution of a biphasic life cycle with alternating diploid and haploid phases. The occurrence of selection during the haploid phase can have far-reaching consequences for fundamental evolutionary processes including the rate of adaptation, the extent of inbreeding depression, and the load of deleterious mutations, as well as for applied research into fertilization technology. Although haploid selection is well established in plants, current dogma assumes that in animals, intact fertile sperm within a single ejaculate are equivalent at siring viable offspring. Using the zebrafish Danio rerio, we show that selection on phenotypic variation among intact fertile sperm within an ejaculate affects offspring fitness. Longer-lived sperm sired embryos with increased survival and a reduced number of apoptotic cells, and adult male offspring exhibited higher fitness. The effect on embryo viability was carried over into the second generation without further selection and was equally strong in both sexes. Sperm pools selected by motile phenotypes differed genetically at numerous sites throughout the genome. Our findings clearly link within-ejaculate variation in sperm phenotype to offspring fitness and sperm genotype in a vertebrate and have major implications for adaptive evolution.真核生物（eukaryotes）开展有性生殖的必然结果，是演化出二倍体与单倍体交替出现的双相生命周期（biphasic life cycle）。单倍体阶段的选择作用，会对多项基础演化过程产生深远影响——涵盖适应速率、近交衰退（inbreeding depression）程度、有害突变（deleterious mutations）负荷，同时也会对受精技术的应用研究产生重要作用。尽管单倍体选择在植物中已得到充分证实，但当前学界主流观点认为，动物单次射精产生的完整可育精子，在孕育可存活后代的能力上并无差异。本研究以斑马鱼（Danio rerio）为实验材料，证实单次射精内完整可育精子间的表型变异所经历的选择，会对子代适合度产生影响。存活时长更长的精子所孕育的胚胎，存活率更高且凋亡细胞（apoptotic cells）数量更少，成年雄性子代的适合度亦更高。这种对胚胎存活力的影响可传递至第二代且无需额外选择，且在雌雄两性中效果相当。通过运动能力表型筛选得到的精子池，在全基因组（genome）的众多位点上均存在遗传差异。本研究结果明确将脊椎动物单次射精内的精子表型变异，与子代适合度及精子基因型直接关联起来，这对适应性演化具有重大意义。