BACKGROUND Natural selection is possible only because all species produce more offsprings than what is needed to maintain the population. Still, the lifetime number of offspring varies widely across species. One may expect natural selection to be stronger in high-fecundity species. Alternatively, natural selection could be stronger in species where a female invests more into an individual offspring. This issue needed to be addressed empirically. RESULTS We analyzed the prevalence of loss-of-function alleles in 35 metazoan species and have found that the strength of negative selection does not correlate with lifetime fecundity or other life-history traits. CONCLUSIONS Higher random mortality in high-fecundity species may negate the effect of increased opportunity for selection. Perhaps, invariance of the strength of negative selection across a wide variety of species emerges because natural selection optimized the life history in each of them, leading to the strongest possible competition. REVIEWERS This article was reviewed by Nicolas Galtier and I. King Jordan.

中文翻译：

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功能丧失的等位基因的患病率与后生动物的终生繁殖力和其他生活史特征无关。

背景技术自然选择是仅可能的，因为所有物种产生的后代超过维持种群所需的后代。尽管如此，后代的终生数量在物种之间差异很大。人们可能希望在高繁殖力物种中自然选择会更强。另外，在雌性对单个后代投入更多的物种中，自然选择可能会更强。这个问题需要凭经验解决。结果我们分析了35个后生动物中功能缺失等位基因的流行情况，发现负选择的强度与终生繁殖力或其他生活史特征不相关。结论高繁殖力物种中较高的随机死亡率可能抵消选择机会增加的影响。也许，由于自然选择优化了每个物种的生活史，从而导致了最强的竞争，因此出现了各种各样物种的否定选择强度的不变性。审阅者本文由Nicolas Galtier和I. King Jordan审阅。