Collaborative Research: Inferring bacterial roles in the evolution of trophic level across the ants

蚂蚁是一种种类繁多的昆虫，数量超过12,000种，组成的生物量比大多数陆地动物都要大。当结合它们作为捕食者、食腐动物和植物和昆虫的捍卫者的角色时，很明显，这些生物是陆地生态系统中更有影响力的动物之一。尽管蚂蚁通常被认为是食肉动物，但它们已经进化成利用各种饮食。值得注意的是，有几个群体已经进入食物链的底层，依赖于提供不足营养的低质量草食饮食。虽然目前还不清楚这些昆虫如何在这样的饮食中坚持下去，但共生细菌被认为发挥了核心作用。这项研究项目将检验这一假设，并调查营养肠道细菌在蚂蚁饮食进化中的作用。利用分子系统发育学，将确定来自不同地理位置的蚂蚁之间的进化关系。将使用稳定同位素来表征这些物种在食物链上的摄食位置，并将使用DNA测序来确定它们的细菌肠道群落的组成。这些结果将被结合起来测试以低质量食物为食的蚂蚁是否与专门的、有益的肠道细菌共同进化，以及栖息地干扰或入侵蚂蚁的引入是否改变了这些动态。这种综合方法不仅将揭示动物宿主塑造细菌群落的特征，还将确定共生细菌是否在蚂蚁饮食的演变中发挥了重要作用，使新的生活方式的起源和在其他不适宜居住的栖息地中的繁殖成为可能。通过研究原始和受干扰的栖息地中的本地和入侵物种，这项工作将揭示环境变化如何改变动物与其肠道微生物之间的相互作用。这类工作对于理解动物物种的适应性具有广泛的重要意义，例如，在应对气候变化方面。该项目将支持对博士后学者、研究生和本科生进行跨学科研究的培训，并通过芝加哥自然历史博物馆为公众提供参与研究的机会。

The ants are a diverse and abundant group of insects, numbering in excess of 12,000 species and comprising a greater biomass than most land-dwelling animals. When combined with their roles as predators, scavengers, and defenders of plants and insects, it is clear that these organisms are among the more influential animals found within terrestrial ecosystems. Although they are often thought of as carnivores, the ants have evolved to utilize a wide range of diets. Notably, several groups have come to feed at the base of the food chain, relying on low-quality, herbivorous diets that provide insufficient nutritional sustenance. While it is not known just how these insects can persist on such diets, symbiotic bacteria are hypothesized to play a central role. This research project will test this hypothesis, and investigate the roles of nutritional gut bacteria in the evolution of ant diets. Using molecular phylogenetics, the evolutionary relationships among ants from several geographic locations will be determined. Stable isotopes will be used to characterize the feeding positions of these species on the food chain, and DNA sequencing will be used to determine composition of their bacterial gut communities. These results will be combined to test whether ants feeding on low-quality diets have co-evolved with specialized, beneficial gut bacteria, and whether habitat disturbance or introductions of invasive ants have changed these dynamics. This synthetic approach will not only reveal features shaping bacterial communities from animal hosts, it will also determine whether symbiotic bacteria have played important roles in the evolution of ant diets, enabling the origins of novel lifestyles and proliferation within otherwise inhospitable habitats. By examining native and invasive species from pristine and disturbed habitats, this work will reveal how environmental changes can alter interactions between animals and their gut microbes. Such work is broadly important to understanding the adaptability of animal species, for example, in dealing with climate change. This project will support the training of a postdoctoral scholar, graduate and undergraduates in interdisciplinary research, and provide opportunities for public involvement in the research through the Chicago Field Museum of Natural History.