Understanding temperature adaptation in tropical insects

如果我们希望了解和减轻气候变化的影响，了解热适应是一个优先事项。生物体目前的耐受性以及它们适应或迁移到新地区的能力将决定它们是否能在变暖的环境中生存下来。与温带物种相比，目前热带物种热适应的数据相对较少。热带昆虫占地球生物多样性的很大一部分，但目前对它们应对气候变化的能力知之甚少。我们建议使用一组研究充分的热带外温动物，Heliconius蝴蝶，评估热适应海拔梯度，以确定这些特征的遗传和环境变化的贡献，并确定潜在的遗传位点。在Heliconius中，有几个亚种的例子也显示出高度的结构。利用群体基因组序列数据和H. melpomene，我们最近表明，三个亚种对H。melpomene和H. ERATO跨越海拔梯度表现出在基因组区域中的差异，该区域包含用于热适应的候选基因，例如代谢酶和热休克蛋白。我们将通过描述种群和物种之间的生理差异来研究这些物种的生理生态学。在厄瓜多尔境内，这些物种在安第斯山脉的东西两侧有平行的海拔梯度，这使我们能够评估我们所确定的任何趋势的可复制性。温度也是界定生态位的一个重要因素，因此也是推动分化和物种形成的一个重要因素。对Heliconius系统的研究主要集中在颜色模式在驱动种群和物种之间分歧中的作用，但栖息地差异也存在，并被认为有助于分歧。例如，物种对H。melpomene和H.位于安第斯山脉西侧的cydno系统已成为物种形成研究中的经典系统，它们显示出不同的海拔范围。表型差异驱动的栖息地利用的分歧还有待调查，但对温度的生理适应似乎很有可能。因此，我们将通过实验测试姐妹分支H之间的热适应差异。melpomene和H. cydno/timareta，以评估温度在决定这些物种的海拔范围和物种分布中的重要性，我们将利用Heliconius广泛的基因组资源进行基因组扫描和详细的关联作图分析，以确定H.美波美识别这些基因座将使我们能够解决这样一个问题，即参与温度适应的基因是否显示出物种间渐渗或趋异选择的证据。不同物种之间的温度适应基因共享可以使物种快速适应新的环境，而分歧则表明热适应在维持物种身份方面非常重要。近年来，对Heliconius的研究蓬勃发展，导致了对基因组中分歧和物种形成过程的许多见解。然而，研究的生态特征在很大程度上仍然局限于颜色模式。该项目将是建立Heliconius作为一个更全面的生态遗传学模型系统的重要一步，利用该系统中现有的知识，基因组资源和技术来研究热带地区更广泛的生态问题。

Understanding thermal adaptation is a priority if we wish to understand and mitigate the impacts of climate change. Organisms' current tolerances and their ability to adapt or move to new areas will determine whether they survive warming environments or not. There is currently a relative paucity of data on thermal adaptation in tropical as compared to temperate species. Tropical insects make up a large proportion of the Earth's biodiversity, but little is currently known about their ability to respond to climate change. We propose to use a well-studied group of tropical ectotherms, the Heliconius butterflies, to assess thermal adaptation across altitudinal gradients, to determine the contributions of genetic and environmental variation to these traits, and to identify the underlying genetic loci. Within Heliconius there are several instances of subspecies that also show structuring by altitude. Using population genomic sequence data and the reference genome for H. melpomene we recently showed that three subspecies pairs of H. melpomene and H. erato across altitudinal gradients exhibit divergence in regions of the genome that contain candidate genes for thermal adaptation such as metabolic enzymes and heat shock proteins. We will characterise the ecophysiology of these species, through characterisation of the physiological differences found between populations and species. Within Ecuador these species have parallel altitudinal clines on the east and west side of the Andes allowing us to assess the replicability of any trends we identify.Temperature can also be an important factor in delimiting the ecological niche and so in driving divergence and speciation. Research on the Heliconius system has largely focussed on the role of colour patterns in driving divergence between populations and species, but habitat differences are also present and thought to contribute to divergence. For example, the species pair H. melpomene and H. cydno on the western side of the Andes, which have become a classic system in speciation research, show divergent altitudinal ranges. The phenotypic differences driving divergence in habitat use have yet to be investigated, but physiological adaptations to temperature seem highly likely. Therefore, we will experimentally test for thermal adaptation differences between the sister clades H. melpomene and H. cydno/timareta, to assess the importance of temperature in determining altitudinal range and species distributions in these species.We will use the extensive genomic resources available for Heliconius to perform genome scans and detailed association mapping analyses to identify loci responsible for thermal adaptation within H. melpomene. Identifying these loci will then allow us to address the question of whether genes involved in temperature adaptation show evidence for either introgression or divergent selection between species. Sharing of temperature adaptation genes between species could allow rapid adaptation to novel environments, while divergence would suggest thermal adaptation is important in maintaining species identities.Research on Heliconius has flourished in recent years leading to many insights into the process of divergence and speciation in the genome. However, the ecological characters investigated have remained largely restricted to colour pattern. This project will be a major step towards establishing Heliconius as a more comprehensive model system for ecological genetics, making use of the existing knowledge, genomic resources and techniques available in this system to investigate broader ecological issues in the tropics.