Postdoctoral Fellowship: OCE-PRF: Understanding population-level genomic and evolutionary impacts of climate change in an anadromous fish species relying on natal homing

在物种水平上，与气候变化相关的范围转移已经在许多分类群中被观察到并提出，在这些分类群中，一个物种通常会向最近极点的有利温度方向移动其范围。然而，沿着物种范围的遗传细分也经常被观察到，这可能意味着由于自然选择和局部适应等因素，亚种群处于不同的进化轨迹上。尽管在许多分类群中观察到物种范围的变化，但由于这样做的困难，我们尚未在这个亚种群水平上记录气候引起的两极范围移动。本项目旨在利用一个溯河产卵鱼类系统内的时间序列遗传数据，在亚种群水平上观察一个物种向两极移动的范围。溯河鱼类出生在淡水环境中，大部分时间生活在海洋环境中，然后回到它们出生的淡水系统繁殖。回到特定的淡水环境可以作为一种自我分类机制，我们可以在两个不同的时间点对它们出生的河流中的鱼进行采样，并评估它们的基因是否在那个时候向极地迁移。该计划将通过指导本科生和初入职业生涯的研究生，以及参加与受美国鲥鱼数量锐减影响的社区有关的当地自然中心的外展活动，扩大人们对科学的参与。遗传漂变和选择是控制种群中等位基因频率的两个主要因素，确定它们的时间和空间趋势有助于深入了解种群或物种的进化驱动因素。空间分化可能表明，例如，由于距离的隔离或沿线的局部适应，而时间分化可能由群体效应、漂移或不断变化的选择压力等因素驱动。我将使用美国鲥鱼研究系统来描述离散种群水平的纬度范围变化，通过评估它们返回产卵的河流系统的中性和适应性分化的时空变化来确定。为了实现这一目标，我将使用链接阅读全基因组测序来检查20年来的样本，以解决以下问题：个别美国鲱鱼种群是否向极地转移了分布？这个问题可以分解为三个具体的问题：（Q1）在非出生河流中繁殖是随机的还是定向的？（Q2）中性分化在种群水平上是否存在跨越多代的变化？（Q3）种群水平上的适应性分化是否存在跨越多代的变化？该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Range shifts at the species level associated with climate change have been observed and proposed in many taxa, where a species will typically move its range towards favorable temperatures in the direction of the nearest pole. However, genetic subdivision along a species’ range is also commonly observed, which may imply that subpopulations are on different evolutionary trajectories due to things like natural selection and local adaptation. Despite observing species range shifts in many taxa, we have yet to document climate-induced poleward range shifting at this subpopulation level due to the difficulty in doing so. This project aims to use time series genetic data within an anadromous fish system to observe poleward range shifting at the subpopulation level for a species. Anadromous fish are born in freshwater environments, live most of their lives in a marine environment, and return to the same freshwater systems where they were born to breed. The return to specific freshwater environments can be leveraged as a self-sorting mechanism where we are able to sample the fish in their natal rivers across two different points in time and assess if their genes have migrated poleward in that time. The PI will broaden participation in science by mentoring undergraduate and early-career graduate students and by participating in outreach events at local nature centers associated with the communities impacted by the collapse of American shad populations. Genetic drift and selection are the two main factors governing allele frequencies in populations and identifying temporal and spatial trends in each provides insights into the evolutionary drivers of populations or species. Spatial differentiation may suggest e.g., isolation by distance or local adaptations along clines, however temporal differentiation may be driven by e.g., cohort effects, drift, or changing selection pressures. I will use the American shad study system to characterize discrete population-level latitudinal range shifts identified by assessing spatiotemporal variation in neutral and adaptive differentiation across river systems they return to for spawning. To accomplish this, I will examine samples spanning 20 years using linked-read whole genome sequencing to address the following question: Have individual American shad populations shifted their distributions poleward? This question can be decomposed into three specific inquiries: (Q1) Is straying to breed in non-natal rivers stochastic or directional? (Q2) Have there been population-level shifts in neutral differentiation spanning multiple generations? (Q3) Have there been population-level shifts in adaptive differentiation spanning multiple generations?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.