Roles of isolation, secondary contact and gene flow in diversification and speciation.

进化生物学最持久的目标之一是了解新物种是如何产生的。由20世纪进化生物学家恩斯特·迈尔（Ernst Mayr）推广的传统观点强调物种形成的地理观点，即大多数新物种的产生或至少是从祖先种群的物理和遗传隔离开始的。最近的理论和实证工作已经从这些基于地理的物种形成观点转向强调机制（例如选择驱动生态分化）的观点，从而对新物种的产生产生重要的见解。然而，我们自己的nserc资助的研究在过去5年中强调了地理隔离和随后的二次接触在大多数脊椎动物物种历史中的普遍存在，反映了对系统地理学文献的全面回顾。因此，我在未来5年由国家自然科学研究委员会资助的研究的长期目标是量化这种长期地理隔离的作用，以及范围动态的后果，特别是二次接触在物种进化和维持中的作用。我提出的NSERC研究重点是北美东部温带地区的一种蛙，春窥蛙（Pseudacris crucifer），我正在将其发展成为物种形成研究的模型系统。我们发表的研究表明，春窥视虫有一个动态的进化史，有6个得到充分支持的进化谱系，它们起源于距今1100万至300万年前不同的、孤立的避难所。在物种分布范围的不同地区，不同的谱系对在不同的分化时期进行了二次接触，大概是在过去的10- 15000年之间。在拟议的研究中，我和我的学生将结合大规模基因组和地理信息系统（GIS）数据、新的统计和建模技术、生物声学分析、回放和杂交实验来解决一系列关于物种形成的研究问题：(I)进化谱系之间的分歧时间与生殖隔离模式（生物物种的标志）之间的关系是什么？（ii）在这个物种的整个历史中，基因组数据对谱系间基因流动的模式说明了什么？（iii）近亲谱系的二次接触是否会产生更有效的生殖障碍，以减少雄性广告叫声的声音干扰（雌性在择偶时使用），或防止适应性不良的杂交？（iv）声环境或季节性的显著差异如何影响不同谱系之间二次接触的结果？(v)世系间杂交的各种适应成本是什么？我的研究项目帮助加拿大站在物种形成研究的前沿，汇集了生物地理学、基因组学、景观生态学和生态遗传学的观点。它为加拿大濒危物种的保护策略提供了重要的输入，例如，如何最好地保留未来多样化和适应的进化潜力，以及系统地理划分是否值得单独指定保护。我概述的培训计划将为遗传学，定量方法，GIS和专业发展方面的至少4名博士，3名硕士和25名学士学生提供一流的机会。正如我过去所做的那样，我将利用我在NSERC研究中积累的专业知识，为加拿大濒危物种的应用景观遗传和保护研究寻求额外的资金和机会。

One of the most enduring goals in evolutionary biology is to understand how new species arise. The traditional view, popularized by 20th Century evolutionary biologist Ernst Mayr, emphasized a geographic view of speciation where most new species arise or at least begin through physical and thus genetic isolation of ancestral populations. Recent theoretical and empirical work has moved away from these geography-based views of speciation to ones that emphasize mechanism (e.g. selection driving ecological divergence) producing important insights into how new species arise. However, our own NSERC-funded research over the last 5 years highlights the pervasiveness of both geographic isolation and subsequent secondary contact in the histories of most vertebrate species, mirroring comprehensive reviews of the phylogeographic literature. Thus, the long-term objective of my NSERC-funded research over the next 5 years is to quantify the role of such long-term geographical isolation, and consequences of range dynamics, and especially secondary contact in the evolution and maintenance of species. My proposed NSERC research focuses on a single temperate eastern North American frog, the spring peeper (Pseudacris crucifer), which I am developing into a model system for speciation studies. Our published work suggests that the spring peeper has a dynamic evolutionary history with 6 well-supported evolutionary lineages that originated in distinct, isolated refugia between 11 and 3 million years before present. Different lineage pairs with disparate times of divergence have come into secondary contact in different parts of the species’ range, presumably within the last 10-15,000 years. In the proposed research, my students and I will combine large-scale genomic and geographic information system (GIS) data, new statistical and modeling techniques, bioacoustical analysis, and playback and hybridization experiments to address a series of research questions on speciation: (i) What is the relation of divergence times between evolutionary lineages and patterns of reproductive isolation, the hallmark of biological species? (ii) What do genomic data say about the patterns of gene flow among lineages over the entire history of this species? (iii) Does secondary contact of closely-related lineages result in more effective reproductive barriers, either to diminish acoustic interference of male advertisement calls (used by females in mate choice), or to prevent maladaptive hybridization? (iv) How might marked differences in the acoustic environment or seasonality shape the outcomes of secondary contact between diverging lineages? (v) What are the various fitness costs of hybridization between lineages? My research program helps put Canada at the forefront of speciation research, bringing together perspectives from biogeography, genomics, landscape ecology, and ecological genetics. It provides important inputs into conservation strategies for Canadian species at risk, for example how best to retain evolutionary potential for future diversification and adaptation, and whether phylogeographic divisions merit separate conservation designation. The training program that I outline will provide premier opportunities for a minimum of 4 PhD, 3 MSc and 25 BSc students in genetics, quantitative methods, GIS, and professional development. As I have done in the past, I will leverage expertise developed with my NSERC research to seek additional funding and opportunities for applied landscape genetic & conservation studies of Canadian species at risk.