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的极点方向移动到有利的温度。然而，遗传细分沿着一个物种的范围也很常见，这可能意味着亚种群由于自然选择和局部适应等原因而处于不同的进化轨迹。尽管在许多类群中观察到物种范围的变化，但由于这样做的困难，我们还没有在这个亚群水平上记录气候引起的向极范围的变化。本项目旨在利用溯河产卵鱼类系统内的时间序列遗传数据，观察一个物种在亚种群水平上的向极范围移动。溯河产卵鱼出生在淡水环境中，大部分时间生活在海洋环境中，然后回到它们出生的同一淡水系统繁殖。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纳塔尔河流中的鱼进行采样，并评估它们的基因是否在那段时间内向极地迁移。PI将通过指导本科生和早期职业研究生，并通过参与与美国沙德人口崩溃影响的社区相关的当地自然中心的外联活动，扩大科学参与。遗传漂变和选择是决定种群中等位基因频率的两个主要因素，识别每个因素的时空趋势可以深入了解种群或物种的进化驱动因素。空间差异可能意味着，通过距离或沿着沿着的局部适应来隔离，然而时间差异可以由例如，群体效应、漂移或不断变化的选择压力。我将使用美国沙德研究系统的特点离散人口水平的纬度范围的变化，通过评估时空变化的中性和适应性分化跨河流系统，他们返回产卵。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跨越20年的样本，以解决以下问题：单个美国沙鱼种群是否将其分布向两极转移？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的流浪是随机的还是定向的？(Q2)在跨越多代的中性分化中是否存在种群水平的变化？(Q3)在跨越多代的适应性分化中是否存在种群水平的变化？该奖项反映了NSF的法定使命，并被认为是值得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的支持。

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.