The evolutionary consequences of environmental uncertainty

自然环境在不断变化，众所周知，这有时会导致进化适应性的极端变化。现存物种是迄今为止在所有环境中幸存下来的少数几个代表。这项由NSERC支持的研究计划的最终目标是帮助理解有机体在不断变化的情况下如何进化。它解决了基本问题，但具有广泛的适用性。例如，传染病致病微生物的进化就是一个适应不断变化的宿主环境的故事。生物体对变化的反应主要有三种方式：1)适应性地“跟踪”不断变化的环境，2)通过一生中的“可塑性”调整，以及3)通过进化出降低彻底失败风险的“对冲”特征。关于这三种反应形式的相对重要性、它们如何相互作用以影响成功，或者它们演变的时间尺度，我们知之甚少。这项由NSERC发现基金资助的研究采用了在实验室和现场进行的理论、观察和实验方法，以促进对生物对不断变化的环境的反应的理解。第一项研究使用计算和实验来询问所谓的押注对冲的演变是如何可能的。根据定义，套期保值的特征在较长时期内是有利的，但在“正常”时期是有害的。一名博士生的目标是发现在正常情况下不“不进化”这种有害的对冲特征的遗传基础；另一名博士生将建立一个计算模型，询问这种限制在更长时间段内的演变情况。第二组项目使用草本植物Lobelia inflata，询问负责表达潜在健康特征的机制。例如，自交交配系统是如何从异交进化而来的？这个问题将通过将该物种与密切相关的异交物种进行比较来解决，并通过公民科学(INaturist)摄影证据来证明整个北卡罗来纳州东部的膨胀螺旋藻交配系统的地理差异。第三组项目重点放在微小的漂浮水生植物Spirodela PolyRha上，它独特地产生耐寒的种子状“郁金香”，沉入沉积物中，使其能够在不可预测的冬季到来时存活下来。春季从沉积物中重新激活的时间受到一种多样化的风险分散策略的影响，这种策略在不同种群之间存在遗传差异。这种植物提供了提出基本问题的机会，这些问题涉及多样性对生存的重要性，以及“生态进化动力学”：多样性的遗传差异对物种间竞争性相互作用结果的影响。这项研究将有助于了解生物对环境变化的反应，包括对灭绝的抵抗力。

Natural environments are continually changing, which is known to cause sometimes extreme variation in evolutionary fitness. Existing species are the few representatives of survivors of all environments to the present time. The ultimate goal of this NSERC-supported research program is to contribute to an understanding of how organisms evolve in the face of continual change. It addresses fundamental questions, but has broad applicability. For example, evolution of infectious disease-causing microbes is a story of adaptation to changing host environments. There are three main ways in which organisms respond to change: 1) by adaptively "tracking" changing environments, 2) through "plastic" adjustments within a lifetime, and 3) by evolving "bet-hedging" traits that reduce risk of complete failure. Little is known about the relative importance of these three forms of response, how they interact to influence success, or the time scales over which they evolve. The research supported by this NSERC Discovery Grant takes theoretical, observational and experimental approaches conducted both in the lab and the field to advance understanding of organismal response to changing environments.    The first study uses computation and experiments to ask how the evolution of so-called bet hedging is even possible. By definition, bet-hedging traits are advantageous over long time periods, but are detrimental during "normal" times. One PhD student aims to discover the genetic basis of not "un-evolving" the detrimental bet-hedging trait during normal times; another will build a computational model to ask about the evolution of such constraints over longer time periods.    A second set of projects uses the herbaceous plant, Lobelia inflata, to ask questions about the mechanisms responsible for expression of traits underlying fitness. For example, how did the self-fertilizing mating system in L. inflata evolve from outcrossing? This question will be addressed by comparing this species with closely related outcrossing species, and through citizen science (iNaturalist) photographic evidence of geographical differences in mating systems of L. inflata across eastern N.A.    The third set of projects focuses on the tiny floating aquatic plant, Spirodela polyrhiza, unique in producing hardy seed-like "turions" that sink to the sediment, allowing survival despite the unpredictable onset of winter. The timing of reactivation from the sediment in the spring is influenced by a diversified risk-spreading strategy, and this strategy differs genetically among populations. This plant offers the opportunity to ask fundamental questions about the importance of diversification for survival, and also about "eco-evolutionary dynamics": the effect of genetic differences in diversification on the outcome of competitive interactions among species. This research will contribute to fundamental knowledge of organismal response to environmental variance, including extinction resistance.