Evolution and Ecology Program, International Institute for Applied Systems Analysis, A-2361, Laxenburg, Austria.
J Theor Biol. 2011 Jun 21;279(1):102-12. doi: 10.1016/j.jtbi.2011.03.001. Epub 2011 Mar 12.
The potential of harvesting to induce adaptive changes in exploited populations is now increasingly recognized. While early studies predicted that elevated mortalities among larger individuals select for reduced maturation size, recent theoretical studies have shown conditions under which other, more complex evolutionary responses to size-selective mortality are expected. These new predictions are based on the assumption that, owing to the trade-off between growth and reproduction, early maturation implies reduced growth. Here we extend these findings by analyzing a model of a harvested size-structured population in continuous time, and by systematically exploring maturation evolution under all three traditionally acknowledged costs of early maturation: reduced fecundity, reduced growth, and/or increased natural mortality. We further extend this analysis to the two main types of harvest selectivity, with an individual's chance of getting harvested depending on its size and/or maturity stage. Surprisingly, we find that harvesting mature individuals not only favors late maturation when the costs of early maturation are low, but promotes early maturation when the costs of early maturation are high. To our knowledge, this study therefore is the first to show that harvesting mature individuals can induce early maturation.
现在越来越多的人认识到收获的潜力可以诱导被开发种群发生适应性变化。虽然早期的研究预测，较大个体的死亡率升高会选择成熟个体的体型变小，但最近的理论研究表明，在某些条件下，体型选择死亡率会导致其他更复杂的进化反应。这些新的预测是基于这样一种假设，即由于生长和繁殖之间的权衡，早期成熟意味着生长减少。在这里，我们通过分析连续时间收获的大小结构种群模型，以及系统地探索三种传统上公认的早期成熟成本（即降低繁殖力、降低生长速度和/或增加自然死亡率）下的成熟进化，扩展了这些发现。我们进一步将这一分析扩展到两种主要的收获选择类型，即个体被捕捞的机会取决于其体型和/或成熟阶段。令人惊讶的是，我们发现，当早期成熟的成本较低时，收获成熟个体不仅有利于晚期成熟，而且当早期成熟的成本较高时，还会促进早期成熟。据我们所知，这项研究首次表明，收获成熟个体可以诱导早期成熟。
