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就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·迈尔推广的传统观点强调了物种形成的地理观点，大多数新物种是在这里产生的，或者至少是通过对祖先种群的物理隔离和遗传隔离开始的。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，选择驱动生态差异)的观点，对新物种是如何产生的产生了重要的见解。然而，我们自己在过去5年由NSERC资助的研究突出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上的普遍性，反映了对系统地理文献的全面审查。因此，我的NSERC资助的研究在未来5年的长期目标是量化这种长期的地理隔离的作用，以及山脉动态的后果，特别是二次接触在物种进化和维持中的作用。我建议的NSERC研究集中在北美东部的一种温带青蛙，春蛙(伪十字花蛙)，我正在将其开发成物种形成研究的模式系统。我们已发表的工作表明，春季偷窥者有一个动态的进化史，有6个得到很好支持的进化谱系，它们起源于距今1100万到300万年前的不同的、孤立的避难所。在物种范围的不同部分，具有不同分歧时间的不同血统对已经进入二次接触，大概在过去的10-15,000年内。在这项拟议的研究中，我和我的学生将结合大规模的基因组和地理信息系统(GIS)数据、新的统计和建模技术、生物声学分析以及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物物种的标志生殖隔离模式之间的关系是什么？(Ii)关于该物种整个历史上各谱系之间的基因流动模式，基因组数据说明了什么？(Iii)密切血统的二次接触是否会导致更有效的生殖障碍，以减少男性广告叫声的声学干扰(女性在选择配偶时使用)，还是防止不适应的杂交？(4)声学环境或季节性的显著差异可能如何影响不同谱系之间二次接触的结果？(V)谱系间杂交的各种适合度成本是多少？我的研究项目帮助加拿大走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战略提供了重要的投入，例如，如何最好地保留未来多样化和适应的进化潜力，以及是否应将系统地理区划单独指定为保护物种。我概述的培训计划将为至少4名博士、3名硕士和25名理学学士学生提供主要机会，学习遗传学、定量方法、地理信息系统和职业发展。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.