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.

尽管后代产出受限，几乎所有多细胞物种均通过有性生殖进行繁衍。有性生殖催生了性选择（sexual selection）——一种在繁殖过程中通过竞争与择偶发挥作用的广泛演化力量，但目前仍不清楚性选择对谱系总适合度（lineage fitness）是有益的，还是会起到制约作用。一方面，性选择可能通过作用于个体优良状态的选择以及突变负荷（mutation load）的清除，最终使拥有更高适合度的谱系获益；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性状之间的投资冲突，抵消潜在的净适合度收益。本研究通过多代入侵实验探究上述观点，以衡量性选择对谱系整体净适合度的影响。我们以赤拟谷盗（Tribolium castaneum）为实验对象，在强、弱两种性选择强度下开展实验进化（experimental evolution），历经77代后，测量了两种处理组的种群在8代时间内入侵同种竞争者种群的整体能力。结果显示，源自强性选择背景的种群具备更优的净适合度，其入侵速度与完成度均优于弱性选择组种群。尽管在入侵实验启动时，这类种群仅占每个混合种群的10%，但源自强性选择历史的定植群体最终几乎实现了完全的基因渐渗（introgression），几乎彻底清除了原始竞争者基因型。利用本实验的设计与参数开展的种群遗传模拟（population genetic simulations）表明，若强性选择同时提升了雌雄两性的幼体与成体适合度，则可解释这一入侵优势。综上，结合实验与建模方法，我们的研究结果揭示：当面临跨多代入侵竞争者种群的广泛挑战时，性选择对种群净适合度具有积极且广泛深远的影响。