Mechanisms of Life History Evolution in an Ancient Vertebrate

“适者生存”指的是自然界中存在着生存和繁殖的竞争。除了形态和生理特征外，生物体的适合性还受到生活史特征的影响(例如，成熟时的年龄和大小、寿命、后代数量)。生活史特征在个体、环境和物种之间表现出巨大的差异，许多研究都致力于了解这些特征的权衡和适应结果。例如，它们在预测人类引起的管理关注物种特定年龄或大小死亡率变化的影响方面非常重要。基因组学的最新进展正在促进对这些特征背后的遗传机制的重要研究。七鳃鳗是一种古老的脊椎动物，发生在生命树的关键分支点之一，是研究生活史进化的优秀模式。活着的七鳃鳗有着高度保守的身体结构，看起来非常像3.6亿年前的七鳃鳗化石，但它们表现出不同的生活史类型。所有七鳃鳗在淡水中长时间的幼虫阶段都会过滤以微生物为食的食物，但在变态后，它们会分化为不同的成体摄食和迁徙类型。在非寄生形式中，它们仍然在其出生的溪流中受到保护，在没有进一步进食的情况下成年性成熟，成虫死亡率很低，但它们较小的身体尺寸限制了产卵量。寄生形式延迟性成熟，迁徙到海洋或大型湖泊以其他鱼类为食；这些形式的生长和繁殖力要高得多，但死亡率也很高。非寄生形式是从寄生形式进化而来的，其中许多物种都受到保护。相反，大西洋中寄生的七鳃鳗在五大湖形成了一种淡水形式，它是一种重大害虫，给商业渔业造成了数十亿美元的损失。*我的研究试图通过调查以下几个方面来确定七鳃鳗摄食和迁徙类型的遗传基础：1)幼体阶段的性腺发育是否决定了‘成体生活史类型’；2)当摄食和迁徙类型分化时，哪些基因在关键发育分支点上被开启或关闭；这项研究具有保护和管理意义(例如，能够预测七鳃鳗在其他淡水系统中入侵的可能性)，并将进一步提高加拿大在鱼类生活史进化方面的声誉。它还将为至少12名学生提供尖端技术(例如，下一代测序)和大型基因组数据集分析方面的技术培训，从而培养出高度胜任学术界和工业界研发工作的人才。

Survival of the fittest' refers to the idea that, in nature, there is competition to survive and reproduce. In addition to morphological and physiological traits, an organism's fitness is affected by life history traits (e.g., age and size at maturity, lifespan, number of offspring). Life history traits show tremendous variation among individuals, environments, and species, and much research has been devoted to understanding the trade-offs and fitness consequences of these traits. They are very important, for example, in predicting the effect of human-induced changes in age- or size-specific mortality rates in species of management concern. Recent advances in genomics are now facilitating important research into the genetic mechanisms underlying these traits.******Lampreys, ancient vertebrates occurring at one of the key branch points in the tree of life, are excellent models to study life history evolution. Living lampreys have a highly conserved body plan, looking very much like fossil lampreys from 360 million years ago, but they exhibit a diversity of life history types. All lampreys filter feed on microscopic organisms during a prolonged larval stage in fresh water but, following metamorphosis, they diverge into different adult feeding and migratory types. In non-parasitic forms, which remain protected within their natal streams and become sexually mature without further feeding, adult mortality rates are low but their small body size limits the number of eggs produced. Parasitic forms delay sexual maturation and migrate to sea or large lakes to feed on other fishes; growth and fecundity are much higher in these forms, but so is mortality. Non-parasitic forms have evolved from parasitic forms, and many of these species are of conservation concern. Conversely, the parasitic sea lamprey in the Atlantic Ocean has given rise to a freshwater form in the Great Lakes, and it is a significant pest causing billions of dollars of damage to the commercial fishery. ******My proposed research seeks to identify the genetic basis of feeding and migratory type in lampreys by investigating: 1) whether gonadal development during the larval stage predetermines' adult life history type; 2) which genes are turned on' or turned off' at the key developmental branch points when the feeding and migratory types diverge; and 3) ways in which the genome of the Great Lakes sea lamprey has diverged from the ancestral Atlantic population since colonization.******This research has conservation and management implications (e.g., to be able to predict the potential for lampreys to become invasive in other freshwater systems), and will further enhance Canada's reputation on life history evolution in fishes. It will also provide at least 12 students with technical training in cutting-edge technologies (e.g., next-generation sequencing) and analysis of large genomic datasets, thus producing personnel highly qualified for employment in research and development in academia and industry.