Evolution and genetic basis of locomotor activity patterns among Lake Malawi cichlids: Exploring a novel mechanism of habitat partitioning

该项目研究了一个新的假设，以解释高度多样性的相似物种如何在同一环境中共存，即物种通过昼夜活动的昼夜节律时间的差异暂时划分其栖息地。动物在一天的过程中表现出一系列的活动水平和模式，但这些行为是如何在遗传水平上受到调节的，人们仍然知之甚少。此外，亲缘关系密切的物种在活动水平和模式上可能存在显著差异，但这些行为的变化如何促进物种在单一环境中的共存，在很大程度上是未知的。该项目利用非洲马拉维湖的慈鲷来解决这两个知识空白。这个慈鲷系统表现出无与伦比的多样性，在过去的1-2百万年里进化了500多种。此外，马拉维慈鲷的多样性非常高，某些地方有40多种。这种情况是如何发生的一直让生物学家着迷，大多数研究都集中在物种如何在空间上划分栖息地，例如跨越不同的深度。这项研究有可能为了解马拉维湖慈鲷系统和其他以高生物多样性为特征的群体如何维持生物多样性提供新的见解，并对保护策略产生影响。更广泛地说，该项目将提供对昼夜节律生物学的更好理解，这可能为人类昼夜节律中断与大脑紊乱之间的联系提供见解。在过去活动的基础上，调查人员将通过与马萨诸塞州现有项目的合作，为缺乏服务和代表性的中学生提供关于进化的夏季讲习班。他们将招募代表性不足的高中生和本科生到他们的实验室进行有监督的研究。此外，他们将为两所大学的本科生开发和提供基于课程的本科生研究体验实验室，以扩大获得研究的机会。活动的昼夜节律对生物体适应性至关重要，动物王国的物种在活动时间上表现出多样性，从强烈的白天到强烈的夜间。虽然动物维持24小时生物钟的神经和分子基础已经得到了充分的研究，但人们对活动时间的演变知之甚少。因此，确定与活动模式变化有关的生态和遗传因素将解决我们知识中的一个关键空白。本项目将通过应用高通量行为分析马拉维湖鲷鱼——生态学和进化研究的一个标志性和强大的模型系统——来研究这些悬而未决的问题。马拉维慈鲷在一系列表型上表现出无与伦比的多样性，包括行为特征。与该提案相关的初步数据记录了物种之间运动活动模式的惊人差异，为研究其进化和遗传基础提供了独特的机会。为此，研究人员将进行实验，在明确的系统发育背景下检查活动模式的进化，评估这些模式受环境因素（包括社会互动和食物供应）调节的程度，并表征运动活动的遗传/基因组结构。虽然每个实验本身都将提供信息，但综合结果将为活动昼夜节律调节的进化潜力提供关键见解，显著推进该领域，并为未来的研究奠定坚实的基础。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This project investigates a new hypothesis to explain how a high diversity of similar species can coexist in the same environment, that species partition their habitat temporally via divergence in the circadian timing of activity, day vs night. Animals exhibit a range of activity levels and patterns over the course of a day, but how these behaviors are regulated at the genetic level remains poorly understood. Further, closely related species can differ markedly in both levels and patterns of activity, but how variation in these behaviors may facilitate the co-existence of species within a single environment is largely unknown. This project addresses these two knowledge gaps, using cichlid fishes from Lake Malawi, Africa. This cichlid system exhibits unparalleled diversity, with well over 500 species evolving within the last ~1-2 million years. Moreover, Malawi cichlids co-exist in extremely high diversities, with certain localities supporting over 40 species. How this occurs has long fascinated biologists, with most studies focusing on how species partition habitat spatially, for example across different depths. This research has the potential to provide novel insights into how biodiversity is maintained in the Lake Malawi cichlid system, and other groups characterized by high levels of biodiversity, with implications for conservation strategies. More broadly, this project will provide a better understanding of circadian biology, which may provide insights into the linkage between disrupted circadian rhythms in humans and disorders of the brain. Building on past activities, the investigators will deliver summer workshops on evolution to underserved and underrepresented middle school students through partnerships with existing programs in Massachusetts. They will recruit underrepresented high school and undergraduate students into their labs for supervised research. In addition, they will develop and deliver course-based undergraduate research experience laboratories for undergraduates at both institutions to expand access to research. The circadian timing of activity is critical for organismal fitness, and species across the Animal Kingdom exhibit diversity in the timing of activity that ranges from strongly diurnal to strongly nocturnal. While the neural and molecular basis through which animals maintain a 24-hour circadian clock is well-studied, much less is known about how the timing of activity evolves. Identifying the ecological and genetic factors associated with variation in activity patterns would therefore address a critical gap in our knowledge. This project will investigate these open questions by applying high-throughput behavioral analyses in Lake Malawi cichlid fishes – an iconic and powerful model system for ecology and evolutionary research. Malawi cichlids exhibit unparalleled diversity in an array of phenotypes, including behavioral traits. Preliminary data associated with this proposal documented a surprisingly high magnitude of variation in locomotor activity patterns among species, offering a unique opportunity to investigate its evolution and genetic basis. To this end, the investigators will undertake experiments to examine the evolution of activity patterns in an explicit phylogenetic context, assess the degree to which these patterns are modulated by environmental factors including social interactions and food availability, and to characterize the genetic/genomic architecture of locomotor activity. While each experiment will be informative on its own, the combined results will provide key insights into the evolutionary potential of circadian regulation of activity, significantly advancing the field, and establishing a robust foundation for future research.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.