The ecological and evolutionary significance of functional variation in mitochondria in a wild animal.

线粒体存在于所有复杂生命的所有细胞中。它们是不寻常的，因为它们携带着自己的DNA的补充，与细胞核分离，这是母系遗传的。几十年的系统地理学研究揭示了线粒体DNA在种群间的强烈差异，并假设变异在进化上是中性的。与此形成鲜明对比的是，Hill （2015 moll . biol）。进化)表明，线粒体变异可能是适应环境变化的基础，因为线粒体可能包含复杂生命中最关键的重要机制（Lane 2016年the Vital Question），它将营养物质转化为可用能量。然而，我们对野生生物线粒体变异的功能后果或其生态和进化意义几乎一无所知（Greenway et al. 2020 PNAS）。三棘棘鱼是探索线粒体变异的杰出模型。它们在实验上是高度可适应的，在它们的分布范围内，线粒体序列表现出实质性的地理差异，有很好的证据表明，在8个主要分支（进化类群）之间的选择存在差异（MacColl未发表）。许多环境的转变（如海洋到淡水和湖泊到河流）都伴随着从一个主要进化支到另一个的转变。其中两个分支，“欧洲”和“大西洋”，在能量处理基因序列上有着特别明显的差异，在苏格兰的北尤斯特岛接触（Dean et al. 2019 moll . biol . evolution）。重要的是，约50%的Uist海洋棘鱼具有大西洋线粒体，另外50%具有欧洲线粒体，没有明显的形态差异，可能是全新世杂交的结果。这提供了一个非常强大和非常不寻常的机会来量化人群中主要线粒体变异的功能后果，同时控制核DNA的差异。在这个项目中，学生将使用多种方法来量化具有欧洲和大西洋线粒体的刺鱼在能量需求、游泳性能、氧气需求和耐温性方面的推定差异。

Mitochondria are present in all cells of all complex life. They are unusual because they carry a complement of their own DNA, separate from the nucleus, which is inherited maternally. Decades of phylogeographic studies, which have revealed strong inter-population divergence in mitochondrial DNA, have assumed that variation is evolutionarily neutral. In stark contrast, Hill (2015 Mol.Biol.Evol) has suggested that mitochondrial variation may be fundamental for adaptation to environmental change, given that mitochondria contain perhaps the most critically important machinery of complex life (Lane 2016 The Vital Question), which converts nutrients into available energy. However, we know almost nothing about the functional consequences of mitochondrial variation in wild organisms, or its ecological and evolutionary significance (Greenway et al. 2020 PNAS). Three-spined stickleback are an outstanding model in which to explore mitochondrial variation. They are highly experimentally amenable and exhibit substantial geographic variation in mitochondrial sequence across their range, with good evidence for differences in selection between eight major clades (evolutionary groupings)(MacColl unpublished). Many environmental transitions (e.g. sea to freshwater and lake to stream) are accompanied by transitions from one major clade to another. Two of these clades, the 'European' and 'Atlantic', with especially distinct differences in energy processing gene sequence, come into contact on the Scottish island of North Uist (Dean et al. 2019 Mol.Biol.Evol). Importantly, ~50% of Uist marine stickleback have Atlantic mitochondria and the other 50% European, with no obvious morphological differences, likely as a result of Holocene hybridisation. This provides an extremely powerful and highly unusual opportunity to quantify the functional consequences of major mitochondrial variation within a population, while controlling for differences in nuclear DNA. In this project the student will use a diversity of approaches to quantify putative differences in energy demand, swimming performance, oxygen demand and temperature tolerance between stickleback with European versus Atlantic mitochondria.