Data from: We happy few: using structured population models to identify the decisive events in the lives of exceptional individuals

In any population, some individuals make it big: they are among the few that produce many offspring, grow to large size, and so on. What distinguishes the lives of these happy few? We present three approaches for identifying what factors distinguish those "lucky" individuals who come to dominate reproduction in a population without fixed differences between individuals (genotype, site quality, etc.): comparing life-history trajectories for lucky and unlucky individuals and calculating the elasticity of the probability of becoming lucky to perturbations in demographic rates at a given size or a given age. As examples we consider published size-structured integral projection models for the tropical tree Dacrydium elatum and the semiarid shrub Artemisia ordosica and an age-size-structured matrix model for the tropical tree Cedrela ordosica. We find that good fortune (e.g., rapid growth) when small and young matters much more than good fortune when older and larger. Becoming lucky is primarily a matter of surviving while others die. For species with more variable growth (such as Cedrela and Ordosica), it is also a matter of growing fast. We focus on reproductive skew, but our methods are broadly applicable and can be used to investigate how individuals come to be exceptional in any aspect.在任何种群中，总有部分个体能获得演化成功：它们属于极少数可繁育大量后代、生长至大型个体的群体，以此类推。这些少数幸运个体的生命历程有何独特之处？我们提出了三种方法，用于甄别在个体间不存在固定差异（如基因型、生境质量等）的种群中，那些最终主导繁殖的“幸运”个体的区分因子：对比幸运与非幸运个体的生活史轨迹，计算在特定体型或特定年龄下，个体成为幸运者的概率对种群统计率扰动的弹性。作为示例，我们采用了已发表的三类模型：针对热带树种鸡毛松（Dacrydium elatum）和半干旱灌木油蒿（Artemisia ordosica）的体型结构积分投影模型（integral projection models），以及针对热带树种洋椿（Cedrela ordosica）的年龄-体型结构矩阵模型。我们发现，个体在体型尚小、年龄尚轻时的好运（如快速生长），远比其在体型偏大、年龄较老时的好运更为关键。成为幸运个体的核心要素，是在其他个体死亡时依然存活下来。对于生长变异度更高的物种（如洋椿与油蒿），快速生长同样是成为幸运个体的关键因素。本研究聚焦于繁殖偏倚（reproductive skew），但我们提出的方法具有广泛适用性，可用于探究个体在任意维度上脱颖而出的成因。