Data from: Lineages evolved under stronger sexual selection show superior ability to invade conspecific competitor populations

Despite limitations on offspring production, almost all multicellular species use sex to reproduce. Sex gives rise to sexual selection, a widespread force operating through competition and choice within reproduction, however, it remains unclear whether sexual selection is beneficial for total lineage fitness, or if it acts as a constraint. Sexual selection could be a positive force because of selection on improved individual condition and purging of mutation load, summing into lineages with superior fitness. On the other hand, sexual selection could negate potential net fitness through the actions of sexual conflict, or because of tensions between investment in sexually selected and naturally selected traits. Here, we explore these ideas using a multigenerational invasion challenge to measure consequences of sexual selection for the overall net fitness of a lineage. After applying experimental evolution under strong versus weak regimes of sexual selection for 77 generations with the flour beetle Tribolium castaneum, we measured the overall ability of introductions from either regime to invade into conspecific competitor populations across eight generations. Results showed that populations from stronger sexual selection backgrounds had superior net fitness, invading more rapidly and completely than counterparts from weak sexual selection backgrounds. Despite comprising only 10% of each population at the start of the invasion experiment, colonizations from strong sexual selection histories eventually achieved near total introgression, almost completely eliminating the original competitor genotype. Population genetic simulations using the design and parameters of our experiment indicate that this invasion superiority could be explained if strong sexual selection had improved both juvenile and adult fitness, in both sexes. Using a combination of empirical and modeling approaches, our findings therefore reveal positive and wide-reaching impacts of sexual selection for net population fitness when facing the broad challenge of invading competitor populations across multiple generations.

尽管后代产出存在局限，但几乎所有多细胞生物都通过有性生殖（sexual reproduction）进行繁衍。有性生殖催生了性选择（sexual selection）——这是一种在繁殖过程中通过竞争与择偶发挥作用的广泛演化动力，但目前学界仍未明确，性选择究竟对谱系总适合度有益，还是会成为演化的制约因素。性选择或许是一种正向动力：它通过筛选优化个体状态、清除突变负荷，最终使谱系获得更优的适合度。但另一方面，性选择也可能通过性冲突（sexual conflict）的作用，或是由于性选择性状与自然选择（natural selection）性状间的投资权衡，抵消潜在的净适合度收益。本研究通过多代入侵挑战实验，探究性选择对谱系整体净适合度的影响，以此检验上述两种假说。本研究以赤拟谷盗（*Tribolium castaneum*）为实验对象，在强、弱两种性选择强度处理下开展了77代实验演化；随后通过8代观测，对比了两组引入种群入侵同种竞争者种群的整体能力。实验结果显示，源自强性选择处理的种群拥有更优的净适合度，其入侵速度与入侵彻底性均优于弱性选择组种群。尽管在入侵实验初始阶段，强性选择组种群仅占总种群的10%，但最终其定植种群几乎实现了完全的基因渐渗（introgression），几乎彻底清除了原竞争者的基因型。基于本实验设计与参数开展的种群遗传模拟显示：若强性选择同时提升了两性的幼体与成体适合度，便可解释上述入侵优势现象。综上，本研究结合实验观测与模型模拟方法证实：当面临多代入侵同种竞争者种群的演化挑战时，性选择对种群净适合度具有积极且广泛的正向影响。