Evolutionary implications of fluctuating natural selection

有人说，自然环境唯一可靠的特征是它们是不断变化的。尽管众所周知，这种变化可以有任何幅度，并可能在任何时间尺度上发生，但关于生物体如何应对这种可变性，仍有许多有待研究。这项由国家科学研究委员会发现基金支持的研究将在对环境变化反应的基本理解方面取得进展。除了灭绝，已知的环境变化的结果包括直接反应，如范围移动和个人层面的可塑性调整在一生中，或者可能包括长期进化的反应，如“适应性跟踪”或风险规避（“下注对冲”）策略的进化。关于单个物种如何孤立地对环境变化作出反应，人们已经了解了很多，但它们的反应在一定程度上取决于它们作为物种组合的一部分如何作出反应。本研究的目标之一是设计一个实验系统，在一个由热梯度组成的“微观世界”中观察物种混合物或组合，然后迫使组合适应这种热梯度的变化。这也将使研究人员能够评估不同的进化和生态过程对结果的相对重要性。其他关于环境变化下生殖进化的研究将为生物体对变化条件的反应提供基础知识。例如，所谓的“下注对冲”是对不可预测的变化本身的一种适应。在一个不可预测的世界里，人类通过“对冲赌注”（购买保险就是一个例子），有意识地做出牺牲眼前收益的决定。由于自然环境也是不可预测的，下注对冲特征预计将通过自然选择进化，因为它们减少了失败的风险。因此，关注环境变化任何方面的人都对这个话题感兴趣。尽管下注套期保值在理论文献中已被认为是对变化的一般反应，但其与应对未来气候变化的相关性尚属首次研究。

It has been said that the only reliable characteristic of natural environments is that they are constantly changing. Although it is well known that such changes can be of any magnitude and may occur over any time scale, much remains to be learned about how organisms cope with this variability. The research supported by this NSERC Discovery Grant will lead to progress in the basic understanding of response to environmental change. Aside from extinction, known outcomes of environmental change include direct responses such as range shifts and individual-level plastic adjustments within a lifetime, or may include long-term evolved responses such as "adaptive tracking" or the evolution of risk aversion ("bet-hedging") strategies over generations. Much is being learned about how individual species may respond to environmental change in isolation, but their response will partly be determined by how they respond when part of a species assemblage. One of the goals of this proposed research is to devise an experimental system to observe species mixtures, or assemblages, in a "microcosm" consisting of a thermal gradient, and then forcing the assemblage to adjust to a change in this thermal gradient. This will also allow the researchers to assess the relative importance of different evolutionary and ecological processes to the outcome. Other studies of the evolution of reproduction under environmental variance will provide fundamental knowledge of organismal response to changing conditions. For example, so-called "bet hedging" is an adaptation to unpredictable change itself. Humans make conscious decisions to sacrifice immediate gain by "hedging their bets" against risk in an unpredictable world (the purchase of insurance is an example). Because natural environments are also unpredictable, bet-hedging traits are expected to evolve through natural selection because they reduce the risk of failure. This topic is thus of interest to those concerned with any aspect of environmental change. Although bet hedging has been acknowledged in the theoretical literature as a general response to change, its relevance to response to future climate change is being studied for the first time.