DISSERTATION RESEARCH: Patterns of Thermal Adaptation

本项目旨在确定热适应模式。为了实现这一目标，研究人员将利用噬菌体G4（一种感染大肠杆菌的病毒）的实验室种群进行进化实验。研究人员将使病毒种群适应高温和低温，通过全基因组测序确定负责适应的突变，并测量进化的噬菌体在宽温度范围内的表现。研究人员将确定适应性突变是否倾向于发生在相同或不同的基因中，并解决两个关于热适应的假设。这些假设是：(1)冷适应病毒的最大生长率低于热适应病毒；(2)适应新的温度会导致不同温度下的性能损失。这两种预测都源于这样一种观点，即在特定温度下，生物化学反应会受到限制，从而限制或降低生物体的表现。自然种群对热变化的适应能力对地理分布和物种生存至关重要。在较短的时间尺度上——日、季或年——热变化往往是可预测的。然而，全球温度的变化意味着未来的热变化可能不那么可预测。对热适应的研究应该会使我们对全球变暖的影响有更深入的了解，并有可能确定有灭绝危险的种群。

This project aims to identify patterns of thermal adaptation. To accomplish this goal, the investigators will conduct evolution experiments using laboratory populations of the bacteriophage G4, a virus that infects the bacterium E. coli. The investigators will adapt virus populations to high and low temperatures, identify the mutations responsible for adaptation by sequencing whole genomes, and measure the performance of the evolved phages over a wide temperature range. The investigators will determine if the adaptive mutations tend to occur in the same or different genes and address two hypotheses concerning thermal adaptation. These hypotheses are: (1) Cold-adapted viruses will have lower maximal growth rates than hotter- adapted viruses; and (2) Adaptation to a new temperature will result in a loss of performance at different temperatures. Both of these predictions stem from the idea that there are constraints on biochemical reactions that limit or reduce an organism's performance at particular temperatures. The ability of natural populations to tolerate thermal variation is crucial to geographic distribution and ultimately to species survival. Over short time scales--daily, seasonally, or yearly--thermal variation has tended to be predictable. However, changing temperatures across the world mean that thermal variation may not be so predictable in the future. The study of thermal adaptation should lead to a greater understanding of the effects of global warming, and it may be possible to identify populations at risk of extinction.