Biodiversity Research Centre and Department of Zoology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada.
Kellogg Biological Station, Department of Plant Biology, and Program in Ecology, Evolutionary Biology and Behavior, Michigan State University, Hickory Corners, Michigan 49060.
Evolution. 2017 Dec;71(12):2930-2941. doi: 10.1111/evo.13374. Epub 2017 Nov 28.
Populations can persist in directionally changing environments by evolving. Quantitative genetic theory aims to predict critical rates of environmental change beyond which populations go extinct. Here, we point out that all current predictions effectively assume the same specific fitness function. This function causes selection on the standing genetic variance of quantitative traits to become increasingly strong as mean trait values depart from their optima. Hence, there is no bound on the rate of evolution and persistence is determined by the critical rate of environmental change at which populations cease to grow. We then show that biologically reasonable changes to the underlying fitness function can impose a qualitatively different extinction threshold. In particular, inflection points caused by weakening selection create local extrema in the strength of selection and thus in the rate of evolution. These extrema can produce evolutionary tipping points, where long-run population growth rates drop from positive to negative values without ever crossing zero. Generic early-warning signs of tipping points are found to have little power to detect imminent extinction, and require hard-to-gather data. Furthermore, we show how evolutionary tipping points produce evolutionary hysteresis, creating extinction debts.
种群可以通过进化在不断变化的环境中持续存在。数量遗传理论旨在预测种群灭绝的环境变化临界率。在这里，我们指出，所有现有的预测实际上都假设了相同的特定适应度函数。该函数导致对数量性状的现有遗传方差的选择随着性状平均值偏离最佳值而变得越来越强。因此，进化的速度没有上限，而种群的持续存在则取决于种群停止增长的环境变化的临界率。然后，我们表明，对基础适应度函数进行合理的生物学改变可以施加一种定性不同的灭绝阈值。特别是，由于选择减弱而导致的拐点在选择强度和进化速度方面产生了局部极值。这些极值可以产生进化转折点，其中长期种群增长率从正值下降到负值，而从不经过零。我们发现，转折点的通用预警信号几乎没有能力检测到即将灭绝的情况，并且需要难以收集的数据。此外，我们展示了进化转折点如何产生进化滞后，从而产生灭绝债务。
