The roles of geographical isolation, secondary contact, and mitonuclear disequilibrium in speciation

生物学中一个持久的挑战是了解新物种是如何产生的，这一挑战早在查尔斯达尔文之前就存在了。虽然物种形成在概念上很简单，涉及到防止不同种群杂交的性状的进化，但存在关键的知识空白。例如，为什么新的姐妹物种开始往往是地理上孤立的种群，是什么选择力量导致了分歧？当孤立的种群重新聚集在一起时会发生什么？这在完成物种形成中发挥了作用吗？什么样的基因变化有助于物种的进化？一个新的想法提出，由核和线粒体基因编码的蛋白质执行关键功能（细胞中的能量产生）在地理上孤立的种群中分化，种群之间的杂交种具有较低的适应性，因为核和线粒体编码的蛋白质不能很好地一起工作。因此，理解物种起源的一个新问题是，这种细胞核协同进化是否会导致物种间杂交功能的丧失。 我们提出的NSERC资助的研究解决了这些问题，重点是春季偷窥者，一种小型北美树蛙。以前的工作揭示了一个动态的进化历史与3核谱系起源于避难所，并明确区的二次接触。我们发现男性广告呼叫和行为的血统之间的差异（从地面或栖息地呼叫）。我们将使用回放实验来测试女性是否感知呼叫差异，石膏模型青蛙评估从栖息地呼叫的生理成本（例如蒸发失水）。在5个已知的接触区，我们将结合联合收割机基因组学，并调用分析和回放，以评估先前隔离的谱系之间接触的结果。我们将使用功能基因组学，生理学和分子进化的方法来测试核和线粒体编码的蛋白质之间的不匹配引起的杂交成本。对于两个同源的春天偷窥，西部和北方合唱蛙，我们将使用生态位建模和基因组学测试的结果，二次接触，如果种间相互作用或非生物因素是更重要的，在塑造物种分布。 这项研究将为至少4名博士，3名硕士和>10名学士学位学生提供基因组学，定量方法和专业发展方面的高级培训。这项工作有助于将加拿大置于物种形成研究的前沿，汇集了基因组学，生理学，地理学和空间生态学的观点。它有助于我们了解是什么因素塑造了物种的分布范围，以及它们如何应对过去的气候变化，并可以为濒危物种的保护策略提供投入;例如，如何最好地保持进化潜力，以及物种的分布如何受到气候变化的影响。我还将利用NSERC的研究，以确保加拿大物种的保护研究的其他机会处于危险之中。

One of the enduring challenges in biology is understanding how new species arise, a challenge that predates Charles Darwin. Although speciation is conceptually simple, involving the evolution of traits that prevent interbreeding of diverged populations, there are key knowledge gaps. For example, why do new sister species often begin as geographically isolated populations and what selective forces cause divergence? What happens when isolated populations come back together, and does this play a role in completing speciation? What genetic changes contribute to the evolution of species? One new idea proposes that proteins encoded by nuclear and mitochondrial genes that perform critical functions (energy production in cells) diverge in among geographically isolated populations, with hybrids between populations having lower fitness because nuclear and mitochondrial encoded proteins do not work well together. Thus a new question for understanding species origins asks if such mitochondrial-nuclear coevolution might cause hybrid disfunction between species. Our proposed NSERC-funded research addresses these questions, focusing on the spring peeper, a small North American treefrog. Previous work reveals a dynamic evolutionary history with 3 nuclear lineages that originated in refugia, and clear zones of secondary contact. We found differences in male advertisement calls and behavior among lineages (calling from the ground or perches). We will use playback experiments to test whether females perceive call differences, and plaster model frogs to assess physiological costs of calling from perches (e.g. evaporative water loss). At 5 known contact zones we will combine genomics, and call analysis and playbacks to evaluate outcomes of contact between previously isolated lineages. We will use functional genomics, physiological, and molecular evolution approaches to test costs of hybridization caused by mismatch between nuclear and mitochondrial encoded proteins. For two congeners of the spring peeper, western and boreal chorus frogs, we will use niche modeling and genomics to test the outcomes of secondary contact, and if interspecific interactions or abiotic factors are more important in shaping species distributions. This research will provide premier training for a minimum of 4 PhD, 3 MSc and >10 BSc students in genomics, quantitative methods, and professional development. This work helps put Canada at the forefront of speciation research, bringing together perspectives from genomics, physiology, biogeography, and spatial ecology. It helps us to understand what factors shape species ranges and how they have shifted in response to past climate change, and can provide inputs into conservation strategies for species at risk; e.g. how best to retain evolutionary potential, and how species' distributions might be affected by climate change. I will also leverage NSERC research to secure other opportunities for conservation studies of Canadian species at risk.