Developmental and Genetic Basis of Life History Variation along a Speciation Continuum

当科学家们试图预测种群将如何对快速的环境变化做出反应时，了解适应和物种形成的遗传基础变得越来越重要。表型可塑性（即单一基因型在不同环境条件下产生不同表型的能力）所起的作用也很重要。表型可塑性可以对新的或不断变化的条件提供即时的种群范围反应，但这种环境诱导的表型如何导致物种形成（它们最终如何成为遗传固定的）尚不清楚。因此，拟议的研究将以七鳃鳗为模型系统，测试遗传和环境因素（即先天与后天）在不同进化阶段的相对重要性。七鳃鳗是一种古老的脊椎动物，具有丰富多样的生命史类型：它们可以寄生于海中或淡水中的其他鱼类身上，甚至更夸张的是，它们可以完全绕过成鱼的摄食阶段，在自己的家乡溪流中进行小规模的繁殖。一些非寄生物种在遗传上不同于它们的寄生祖先；在其他情况下，不同的迁徙和摄食类型显示很少或没有遗传分化（即，代表分化的早期阶段）。似乎单个物种可以产生不同的生活史类型，但这是由于遗传多态性还是表型可塑性尚不清楚。拟议的研究将是第一个使用互补发育（例如，在共同实验室条件下饲养不同喂养方式的后代）和遗传方法来测试这一点的研究。了解生命周期多样性的基础具有重要的管理意义（例如，了解是什么使海七鳃鳗成为五大湖的入侵物种）。在预计气候驱动的变化对海洋和淡水系统的相对生产力造成影响的背景下，能够预测淡水系统在什么条件下可能再次发生入侵尤为重要。这项研究将为学生提供尖端基因组技术方面的培训，培养在学术界和工业界从事研发工作的高素质人才。

As scientists try to predict how populations will respond to rapid environmental change, it is becoming increasingly important to understand the genetic basis of adaptation and speciation. The role played by phenotypic plasticity (i.e., the ability of a single genotype to produce different phenotypes under different environmental conditions) is also important. Phenotypic plasticity can provide an immediate population-wide response to new or changing conditions, but how such environmentally-induced phenotypes lead to speciation (how they eventually become genetically fixed) is less clear. The proposed research will therefore test the relative importance of genetic and environmental factors (i.e., nature versus nurture) at different stages of evolution, using lampreys as a model system. Lampreys are ancient vertebrates which exhibit a rich diversity of life history types: they may feed parasitically on other fishes either at sea or in fresh water or, even more dramatically, may bypass the adult feeding phase altogether and reproduce at small sizes in their home streams. Some nonparasitic species are genetically distinct from their parasitic ancestor; in other cases, different migratory and feeding types show little or no genetic differentiation (i.e., represent the early stages of divergence). It appears that a single species may produce different life history types, but whether this is due to genetic polymorphism or phenotypic plasticity is unknown. The proposed research will be the first to test this, using complementary developmental (e.g., rearing offspring of different feeding types under common laboratory conditions) and genetic approaches. Understanding the basis of life cycle diversity has significant management implications (e.g., understanding what enabled the sea lamprey to become invasive in the Great Lakes). Being able to predict under what conditions invasion of fresh water systems could happen again is particularly important in the context of expected climate-driven changes to the relative productivity of marine and freshwater systems. This research will provide students with training in cutting-edge genomic technologies, producing personnel highly qualified for employment in research and development in academia and industry.