Data from: Complex patterns of multivariate selection on the ejaculate of a broadcast spawning marine invertebrate

Assessing how selection operates on several, potentially interacting, components of the ejaculate is a challenging endeavour. Ejaculates can be subject to natural and/or sexual selection, which can impose both linear (directional) and nonlinear (stabilizing, disruptive and correlational) selection on different ejaculate components. Most previous studies have examined linear selection of ejaculate components and, consequently, we know very little about patterns of nonlinear selection on the ejaculate. Even less is known about how selection acts on the ejaculate as a functionally integrated unit, despite evidence of covariance among ejaculate components. Here we assess how selection acts on multiple ejaculate components simultaneously in the broadcast spawning sessile invertebrate Mytilus galloprovincialis using the statistical tools of multivariate selection analyses. Our analyses of relative fertilization rates revealed complex patterns of selection on sperm velocity, motility and morphology. Interestingly, the most successful ejaculates were made up of slower-swimming sperm with relatively low percentages of motile cells, and sperm with smaller head volumes that swam in highly pronounced curved swimming trajectories. These results are consistent with an emerging body of literature on fertilization kinetics in broadcast spawners, and shed light on the fundamental nature of selection acting on the ejaculate as a functionally integrated unit.评估选择如何作用于精液（ejaculate）中多个潜在相互作用的组分，是一项极具挑战性的工作。精液可受到自然选择和/或性选择的作用，这类选择可对不同的精液组分施加线性（定向）与非线性（稳定化、破坏性及相关）选择。既往绝大多数研究仅关注精液组分的线性选择，因此我们对精液所受非线性选择的模式知之甚少。尽管已有证据表明精液组分间存在协方差，但对于选择如何作为功能整合单元作用于整个精液的相关研究则更为匮乏。本研究以营广播式产卵的固着无脊椎动物地中海贻贝（Mytilus galloprovincialis）为研究对象，借助多变量选择分析的统计工具，评估选择如何同时作用于多个精液组分。我们对相对受精率的分析结果显示，选择对精子速度、活力及形态呈现出复杂的作用模式。值得注意的是，受精成功率最高的精液由两类精子构成：一类是游动速度较慢、活力细胞占比相对较低的精子，另一类是头部体积更小、游动轨迹弯曲程度极高的精子。本研究结果与近年来不断涌现的广播式产卵生物受精动力学相关文献相符，同时也阐明了作为功能整合单元的精液所受选择作用的本质特征。