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

在许多分类群中已经观察到并提出了与气候变化相关的物种水平的范围转移，其中一个物种通常会将其范围向最近极点方向的有利温度移动。然而，沿着物种范围的遗传细分也是常见的，这可能意味着由于自然选择和局部适应等原因，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了物种范围的变化，但由于很难做到这一点，我们还没有记录下气候导致的极地范围在这个亚种群水平上的变化。这个项目的目的是利用顺河鱼类系统中的时间序列遗传数据来观察一个物种在亚种群水平上向极地移动的范围。淡水鱼出生在淡水环境中，生活在海洋环境中的大部分时间，并返回到它们出生繁殖的相同淡水系统。回到特定的淡水环境可以作为一种自我分选机制，我们能够在两个不同的时间点对它们出生的河流中的鱼进行采样，并评估它们的基因在这段时间内是否向极地迁移。PI将通过指导本科生和职业生涯早期的研究生，以及通过参加与受美国鲑鱼种群崩溃影响的社区相关的当地自然中心的外联活动，扩大对科学的参与。遗传漂移和选择是控制种群中等位基因频率的两个主要因素，识别两者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。空间分化可以暗示，例如，通过距离或沿斜坡的局部适应来隔离，然而，时间分化可以由例如队列效应、漂移或变化的选择压力来驱动。我将使用美国沙鱼研究系统来表征离散的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中中性和适应性差异的时空变化来确定。为了实现这一点，我将使用连锁阅读全基因组测序技术研究跨越20年的样本，以解决以下问题：个别美国沙斑鱼种群是否向极地转移了它们的分布？这个问题可以分解为三个具体的问题：(Q1)在非天然河流中流浪繁殖是随机的还是定向的？(Q2)在跨越多代人的中性分化中，是否存在种群水平的变化？(Q3)在跨越多代人的适应性分化方面是否存在人口水平的变化？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。

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.