Diversification, adaptation and speciation in a temperate frog

尽管半个多世纪以来，我们对物种形成机制的理解取得了令人难以置信的进步，但仍然存在一些悬而未决的问题。特别是，我们缺乏关于在整个单一物种范围内进化谱系（物种形成的标志）之间交配障碍的地理和时间序列的综合信息。冰川作用下的山脉破碎是如何最终影响到生殖隔离屏障的进化的？在长时间分离的谱系接触后，对杂交的选择是否增强了交配偏好的差异，这一过程被称为强化？在不同的生态选择和有限的扩散情景下，交配系统的差异，特定的繁殖物候（繁殖活动的顺序）是否会在细微的尺度上产生？我们通过对一种北美小青蛙——春窥视蛙的基因和实验研究来解决这些问题。在我们的第一个项目中，我们确定了整个物种范围内不同谱系之间的主要次级接触区，并将测试(1)谱系之间配偶识别系统的关键差异，(2)雄性呼叫和雌性偏好差异的遗传基础，(3)杂种遗传不相容的证据，以及(4)次级强化的证据。我们的第二个项目将研究可能导致这种差异的生态机制。特别是在2500平方米的环境中。我们将测试在不同植被结构和小气候的生境中，选择压力是否会在(1)雄性的春季出现和鸣叫时间以及(2)雄性广告鸣叫的声学特性上产生显著差异。从这些项目中获得的综合见解将促进我们对物种形成中地理隔离、接触带动态和生态选择之间相互作用的认识。总之，我们的研究结果说明了气候变化已经并将在未来改变进化轨迹。这项研究为至少44名学生提供了进化生态学方面的特殊培训。

Despite over a half-century of incredible advances in our understanding of speciation mechanisms, there remain outstanding issues. In particular we lack comprehensive information on the geography and temporal sequence for the evolution of barriers to mating between evolutionary lineages [the hallmarks of speciation] across the entire range of single species. How has range fragmentation, precipitated by glaciations, ultimately impacted the evolution of reproductive isolating barriers? Does selection against hybridization after contact of long sundered lineages enhance differences in mating preferences, a process called reinforcement? Can differences in the mating system, particular breeding phenology (sequence of breeding activities), arise at fine scales under divergent ecological selection and restricted dispersal scenarios? We address these questions using genetic and experiment studies of a small North American frog, the spring peeper. For our first project, we identified major secondary contact zones between different pairs of lineages throughout the species' range, and will test for (1) key differences in the mate recognition system between lineages, (2) the genetic basis for male call and female preference differences for them, (3) evidence for genetic incompatibilities in hybrids, and (4) evidence for secondary reinforcement. Our second project will examine the ecological mechanisms that may cause such divergence. Specifically within an environmentally heterogeneous 2500 sq. km. area in Eastern Ontario, we will test whether selection pressures in habitats differing in vegetation structure and microclimate can produce significant differences in (1) spring emergence and calling times of males, and (2) the acoustic properties of male advertisement calls. Combined insights from these projects will advance our knowledge of the interplay among, geographical isolation, contact zone dynamics, and ecological selection in speciation. Together our results speak to how climate change has and can in the future alter evolutionary trajectories. The research provides exceptional training in evolutionary ecology for a minimum of 44 students.