Simons A M, Johnston M O
Department of Biology, College of Natural Sciences, Carleton University, Ottawa, Ontario, K1S 5B6 Canada.
J Evol Biol. 2003 Mar;16(2):233-43. doi: 10.1046/j.1420-9101.2003.00530.x.
Age and size at reproduction are important components of fitness, and are variable both within and among angiosperm species. The fitness consequences of such life-history variation are most readily studied in organisms that reproduce only once in their lifetime. The timing of the onset of reproduction (bolting) in the monocarpic perennial, Lobelia inflata, occurs over a range of dates within a season, and may be postponed to a later year. Empirical relationships among life-history traits, derived from over 950 wild-growing and experimentally manipulated plants in the field, are used to model an optimal changing size threshold (norm of reaction) for bolting over the growing season. Comparisons are made between observed and expected norms of reaction governing bolting. An apparently suboptimal bolting schedule that precludes bolting beyond an early (conservative) date is observed, and is found to be qualitatively consistent with conservative bet hedging under unpredictable season lengths. On this basis we propose the schedule of bolting as a plausible example of a conservative bet-hedging strategy. The results underscore the critical need for long-term studies of fluctuating selection to distinguish suboptimality from bet hedging.
繁殖时的年龄和大小是适合度的重要组成部分，并且在被子植物物种内部和物种之间都存在差异。这种生活史变异对适合度的影响在一生中只繁殖一次的生物体中最容易研究。一年生多年生植物充气半边莲（Lobelia inflata）的繁殖起始时间（抽薹）在一个季节内的一系列日期出现，并且可能推迟到下一年。从950多种野外生长和实验操纵的植物中得出的生活史特征之间的经验关系，被用于模拟整个生长季节抽薹的最佳变化大小阈值（反应规范）。对控制抽薹的观察到的和预期的反应规范进行了比较。观察到一个明显次优的抽薹时间表，该时间表排除了在早期（保守）日期之后抽薹的情况，并且发现其在质量上与在不可预测的季节长度下的保守风险对冲一致。在此基础上，我们提出抽薹时间表是保守风险对冲策略的一个合理例子。结果强调了对波动选择进行长期研究以区分次优性和风险对冲的迫切需求。
