DISSERTATION RESEARCH: Tracking trends in the lichen symbiosis: do species interactions drive the latitudinal diversity gradient?

纬度多样性梯度是在赤道附近的热带地区发现许多物种的模式，而在热带以外的北极和南极发现的物种较少。这种模式通常用温度、气候或地质条件来解释。纬度梯度较少用生物相互作用来描述，即不同生物体之间的相互作用。这项研究调查了一种特殊的生物相互作用，即地衣共生，沿着从北美到南美的大环境梯度。地衣是真菌和藻类/蓝藻之间的共生体(互惠的、长期的、密切的物理联系)。地衣虽然很小，而且经常被忽视，但几乎在每一个陆地环境中都可以找到，这使得它们成为研究大环境梯度上的生物相互作用的理想选择。这项研究将重点放在共生在驱动多样性模式方面的作用，并可能改进对面对持续的气候变化时多样性模式如何变化的预测。这项研究独特地解决了共生中的两个伙伴，并将通过发现和描述新物种和新特征来增加我们对全球生物多样性的了解。这个项目将通过支持从描述性模式到机械化过程的研究来扩展博士生的研究和培训。密歇根州将向本科生提供一个关于共生的研讨会，高中课堂的教育材料将通过Data Nugget计划提供，以促进科学进程，并可能在大学层面招收更多的科学和技术专业的学生。生物相互作用假说认为，在非热带地区，非生物选择压力的作用力更大，而在热带地区，生物选择压力的作用力更大。此外，这些生物相互作用导致适应和共同进化竞赛的高峰移动，这进一步促进了热带地区的多样性。这项研究通过对沿纬度梯度发现的五个地衣形成真菌家族中的真菌和藻类伙伴进行测序，研究地衣共生的动态，以便绘制伙伴之间的特异性模式，并测试伙伴切换是否导致地衣共生的多样化事件或范围转移。

The latitudinal diversity gradient is the pattern in which many species are found in the tropics, near the equator, and fewer species are found outside of the tropics, towards the North and South poles. This pattern is often explained in terms of temperature, climate, or geological conditions. Less frequently, the latitudinal gradient is described in terms of biotic interactions; interactions between different organisms. This research investigates a particular biotic interaction, the lichen symbiosis, along a large environmental gradient from North to South America. Lichens are symbioses (mutually beneficial, long-term, close physical associations) between fungi and algae/cyanobacteria. Though small and often overlooked, lichens can be found in almost every terrestrial environment, making them ideal for investigating biotic interactions across large environmental gradients. This research will focus on the role of symbiosis in driving patterns of diversity, and may improve predictions of how patterns of diversity change in the face of ongoing changes in climate. This research uniquely addresses both partners in the symbiosis, and will increase our knowledge of global biodiversity through the discovery and description of new species and traits. This project will extend the research and training of a doctoral student by supporting research that moves from descriptive pattern to mechanistic process. A workshop on symbioses will be made available to undergraduate students in Michigan, and educational materials for high school classrooms will be offered via the Data Nugget program, promoting the scientific process and potentially recruiting more students to science and technology at the college level. The biotic interactions hypothesis proposes that in extra-tropical regions, abiotic selective pressures exert a stronger force, whereas in tropical regions, biotic selective pressures exert a stronger force. Furthermore, these biotic interactions lead to moving peaks of adaptation, and coevolutionary races, which further contributes to diversification in the tropics. This research investigates the dynamics of the lichen symbiosis along a latitudinal gradient by sequencing both the fungal and algal partners within five lichen-forming families of fungi found along the latitudinal gradient in order to map patterns of specificity among partners, and to test whether partner switches have resulted in diversification events or range shifts in the lichen symbiosis.