Data from: The continuum between semelparity and iteroparity: plastic expression of parity in response to season length manipulation in Lobelia inflata.

Background: Semelparity and iteroparity are considered to be distinct and alternative life-history strategies, where semelparity is characterized by a single, fatal reproductive episode, and iteroparity by repeated reproduction throughout life. However, semelparous organisms do not reproduce instantaneously; typically reproduction occurs over an extended time period. If variation in reproductive allocation exists within such a prolonged reproductive episode, semelparity may be considered iteroparity over a shorter time scale.This continuity hypothesis predicts that “semelparous” organisms with relatively low probability of survival after age at first reproduction will exhibit more extreme semelparity than those with high probability of adult survival. This contrasts with the conception of semelparity as a distinct reproductive strategy expressing a discrete, single, bout of reproduction, where reproductive phenotype is expected to be relatively invariant. Here, we manipulate expected season length—and thus expected adult survival—to ask whether Lobelia inflata, a classic “semelparous” plant, exhibits plasticity along a semelparous-iteroparous continuum. Results: Groups of replicated genotypes were manipulated to initiate reproduction at different points in the growing season in each of three years. In lab and field populations alike, the norm of reaction in parity across a season was as predicted by the continuity hypothesis: as individuals bolted later, they showed shorter time to, and smaller size at first reproduction, and multiplied their reproductive organs through branching, thus producing offspring more simultaneously. Conclusions: This work demonstrates that reproductive effort occurs along a semelparous-iteroparous continuum within a “semelparous” organism, and that variation in parity occurs within populations as a result of phenotypic plasticity.背景：单次生殖（semelparity）与多次生殖（iteroparity）被视作两种截然不同且互斥的生活史策略：单次生殖以单次生殖后个体死亡为典型特征，而多次生殖则指在整个生命周期内可重复开展生殖活动。不过，单次生殖生物并非瞬间完成生殖过程，通常其生殖活动会持续较长时长。若在这类延长的生殖周期内存在生殖分配的变异，那么单次生殖便可在更短的时间尺度上被归类为多次生殖。 该连续性假说预测：相较于成年存活率较高的类群，“单次生殖”生物中首次生殖后存活概率相对较低的个体，会表现出更为极端的单次生殖特征。这与将单次生殖视为一种离散、单一的生殖策略的传统认知相悖——传统观点认为单次生殖的表型相对固定。 本研究通过操控预期季节长度——进而调控预期成年存活率——探究经典“单次生殖”植物吹箫半边莲（Lobelia inflata）是否存在沿单次-多次生殖连续谱的表型可塑性。 结果：三年间，我们对多个重复基因型群体分别在生长季的不同节点启动生殖过程。无论是实验室种群还是野外种群，沿季节梯度的生殖模式反应规范均符合连续性假说的预测：随着个体抽薹时间延后，其首次生殖所需时长更短、首次生殖时的体型更小，且通过分枝增殖生殖器官，最终使子代产出更为同步。 结论：本研究证实，在被归类为“单次生殖”的生物体内，生殖投入确实存在沿单次-多次生殖连续谱的梯度变化；种群内的生殖模式变异实则由表型可塑性介导。