Selection experiments and sequencing to identify mechanisms of thermal adaptation in a splash pool copepod

耐热性是一个重要的特征，因为它影响到一个物种可以在哪里生活，以及它是否能在变暖的气候中生存。不同物种的耐热性不同，但人们对导致某些动植物比其他动植物更耐热的遗传差异知之甚少。本研究将以小型海洋甲壳类动物卡氏虎为实验模型，研究基因变化导致耐热性增加的原因。研究人员将进行一系列进化实验，在实验室中，他们将人工选择提高老虎耐热性的物种。在实验结束时，他们将对实验种群的基因组进行排序，以检查哪些基因变化导致了更强的耐热性。然后，他们将把这些基因变化与虎狮北方和南方种群之间的差异进行比较，这两个种群的耐热性自然不同，以测试相同的变化是否导致实验室和自然界耐热性的提高。这项研究将有助于更好地理解为什么一些物种比其他物种更耐热，从而提高预测哪些物种将更容易受到气候变化影响的能力。对导致更强耐热性的遗传变化的了解也可以用于水产养殖和保护性育种计划，以确定给定物种的哪些菌株最有可能对变暖具有弹性。耐热性特征控制着生物在不同环境中的丰度和分布，并塑造生物对气候变化的反应。然而，对大多数物种来说，决定耐热性变异的机制却知之甚少。飞溅池桡足类虎脚类在不同种群之间表现出不同的耐热性特征，很容易在实验室杂交和饲养。因此，它是研究温度适应机制的一个很好的模型。研究人员将进行三个选择实验，每个实验针对老虎种群不同的热性能方面：(A)致死上限，(B)热极限的可塑性，和(C)热最优。他们将把这些实验与生理测量、转录组图谱和全基因组重测序结合起来，以确定热适应各个方面的潜在机制。最后，他们将把实验室实验的结果与北美和南美洲分布在平行温度梯度上的两种老虎物种的种群重新排序数据进行比较。该项目的结果将提供该物种温度适应的遗传和生理基础的全面图谱，并阐明关键问题，包括基因调节与蛋白质编码变化在种群之间生理差异中的作用，参与温度适应的基因组比例，热宽度增加的进化带来的成本和权衡，以及平行环境梯度的适应的重复性。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Heat tolerance is an important trait, because it influences where a species can live, and whether it will survive in a warming climate. Heat tolerance varies among species, but little is understood about the genetic differences that make some animals and plants more heat tolerant than others. This research will use the small marine crustacean, Tigriopus californicus, as an experimental model to investigate the genetic changes lead to increased heat tolerance. The researchers will conduct a series of evolution experiments, where they will artificially select for increased heat tolerance in Tigriopus in the laboratory. At the end of the experiments they will sequence the genomes of the experimental populations to examine which genetic changes led to greater heat tolerance. Then they will compare these genetic changes to differences among northern and southern populations of Tigriopus, which naturally differ in their heat tolerance, to test whether the same changes are responsible for increased heat tolerance in the lab and in nature. This research will contribute a greater understanding of why some species are more heat tolerant than others, leading to an improved ability to predict which species will be more vulnerable to climate change. An understanding of the genetic changes that lead to greater heat tolerance could also be used in aquaculture and in conservation breeding programs, to identify which strains of a given species are the most likely to be resilient to warming.Thermal tolerance traits govern the abundance and distribution of organisms across environments and shape organismal responses to climate change. However, mechanisms determining variation in thermal tolerance are poorly understood for most species. The splash pool copepod Tigriopus californicus exhibits divergent thermal tolerance traits across populations, and is easily crossed and reared in the lab. As a result, it is an excellent model for examining mechanisms of temperature adaptation. The researchers will perform three selection experiments, each targeting a different aspect of thermal performance that differs among Tigriopus populations: (A) upper lethal limits, (B) plasticity of thermal limits, and (C) thermal optima. They will combine these experiments with physiological measurements, transcriptome profiling, and whole-genome resequencing to identify mechanisms underlying each aspect of thermal adaptation. Finally, they will compare results of laboratory experiments to population resequencing data for two Tigriopus species distributed over parallel temperature gradients in North and South America. Results of this project will provide a comprehensive map of the genetic and physiological bases of temperature adaptation in this species, and shed light on key questions, including the role of gene regulation vs. protein coding changes in physiological divergence among populations, the proportion of the genome involved in temperature adaptation, the costs and trade-offs imposed by the evolution of increased thermal breadth, and the repeatability of adaptation across parallel environmental gradients.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.