Phylogenomic Study of Adaptive Radiation in Antarctic Fishes

了解生物群体对气候变化的反应对于评估人类活动的影响以及了解过去的气候变化如何在很长一段时间内塑造了生物多样性至关重要。占据南极洲近岸海洋栖息地的鱼类主要是一组近亲物种，叫做南极鱼。南极气候的剧烈变化似乎对这种具有重要经济意义的鱼类的起源和进化多样化起到了重要作用。南极洲的鱼类化石沉积物形成于该大陆温度较温和的时期，这表明该地区是鱼类谱系更为多样化的家园。今天，南大洋的海水非常寒冷，经常低于冰点，但南极鱼表现出许多适应这种恶劣海洋栖息地的能力，包括抗冻蛋白质的存在。该研究项目将收集数百个基因的DNA序列，以推断几乎所有124种南极鱼的谱系关系，并使用数学技术来估计物种和谱系的年龄。关于南极鱼进化分化时间的知识将使研究人员能够评估南极洲以前主要气候变化的时间是否与现代南大洋鱼类动物群形成的关键事件相关。该项目还将进一步实现国家科学基金会的目标，即让公众获得科学发现，并培养新一代的科学家。该项目将通过自然历史博物馆展览和其他公开讲座，支持面向青少年群体和公众的教育推广活动。它将为研究生和博士后研究学者提供专业培训机会。适应性辐射主要是在岛屿生态系统中研究的，其中谱系经历了与生态分化相一致的高进化多样化率。南极鱼在南大洋的鱼类动物群中占主导地位，并表现出抗冻糖蛋白，使其能够占领零度以下的水域。南极鱼被认为是海洋鱼类中适应辐射的唯一例子之一，但其多样化和辐射进入不同生态栖息地的进化史尚不清楚。本研究将对目前已发现的124种南极鱼进行物种系统发育（进化史）分析，以探讨该谱系中适应辐射的机制。系统发育是通过下一代DNA测序和相关技术从大约350个基因样本中推断出来的。博物馆标本的形态计量学数据用于研究形态多样化的速度，并确定谱系多样化率与形态差异的起源之间是否存在相关性。将南极鱼辐射的谱系、形态和生态多样化模式与古气候记录进行比较，以确定过去的全球气候变化是否塑造了这种极地适应鱼类谱系的进化多样化。

Understanding how groups of organisms respond to climate change is fundamentally important to assessing the impacts of human activities as well as understanding how past climatic shifts have shaped biological diversity over deep stretches of time. The fishes occupying the near-shore marine habitats around Antarctica are dominated by one group of closely related species called notothenioids. It appears dramatic changes in Antarctic climate were important in the origin and evolutionary diversification of this economically important lineage of fishes. Deposits of fossil fishes in Antarctica that were formed when the continent was experiencing milder temperatures show that the area was home to a much more diverse array of fish lineages. Today the waters of the Southern Ocean are very cold, and often below freezing, but notothenioids fishes exhibit a number of adaptions to live in this harsh set of marine habitats, including the presence of anti-freeze proteins. This research project will collect DNA sequences from hundreds of genes to infer the genealogical relationships of nearly all 124 notothenioid species, and use mathematical techniques to estimate the ages of species and lineages. Knowledge on the timing of evolutionary divergence in notothenioids will allow investigators to assess if timing of previous major climatic shifts in Antarctica are correlated with key events in the formation of the modern Southern Ocean fish fauna. The project will also further the NSF goals of making scientific discoveries available to the general public and of training new generations of scientists. The project will support educational outreach activities to teenager groups and to the general public through a natural history museum exhibit and other public lectures. It will provide professional training opportunities for graduate students and a postdoctoral research scholar. Adaptive radiation, where lineages experience high rates of evolutionary diversification coincident with ecological divergence, is mostly studied in island ecosystems. Notothenioids dominate the fish fauna of the Southern Ocean and exhibit antifreeze glycoproteins that allow occupation of the subzero waters. Notothenioids are noted as one of the only examples of adaptive radiation among marine fishes, but the evolutionary history of diversification and radiation into different ecological habitats is poorly understood. This research will generate a species phylogeny (evolutionary history) for nearly all of the 124 recognized notothenioid species to investigate the mechanisms of adaptive radiation in this lineage. The phylogeny is inferred from approximately 350 genes sampled using next generation DNA sequencing and related techniques. Morphometric data are taken for museum specimens to investigate the tempo of morphological diversification and to determine if there are correlations between rates of lineage diversification and the origin of morphological disparity. The patterns of lineage, morphological, and ecological diversification in the notothenioid radiation will be compared to the paleoclimatic record to determine if past instances of global climate change have shaped the evolutionary diversification of this lineage of polar-adapted fishes.