Wilkins, Rachel Lynn2022-10-312022-10-312022-08Wilkins_cornellgrad_0058F_13299http://dissertations.umi.com/cornellgrad:13299https://hdl.handle.net/1813/112087181 pagesDescribing species distributions patterns and understanding the mechanisms responsible for producing those patterns is a fundamental aspect of ecology. The positive relationship between local abundance and regional occupancy of an assemblage of species is among the most ubiquitous patterns in nature, however the mechanisms that produce such a pattern are varied. We conducted two meta-analyses of the correlation-coefficients and slopes of abundance-occupancy relationships (AORs) to explain the mechanisms that govern species distributions in aquatic systems. We found AORs are stronger among habitats and organisms with elevated dispersal potential and wider niche breadths. We found consistent slopes of AORs among all aquatic systems, suggesting abundance and occupancy are similarly coupled. Exploring the differences between species can help us understand the reasons species fall along specific regions of AORs. To understand the drivers of the disparity in occurrence between two species, I studied the difference in environmental condition, diet, and population genetic structure, of two diaptomid copepod species, one common and one rare. Differences in occurrence between these two species is not due to a difference in diet, but may be due to different levels of dispersal, and local adaptation to a wide range of environmental conditions. Variation in diet based on lake conditions suggests diaptomid copepods play a complex role in lake food webs. To understand how diaptomid copepods diets vary according to lake environmental conditions, we measured trophic position in five species of diaptomid copepod from 43 lakes. Copepods had a variable and predominantly predatory diet, that changed given the trophic state or size of the lake. For diaptomid copepods, responding to various environmental conditions through dispersal and diet provide insight into the mechanisms underlying distribution patterns, and the fundamental drivers of patterns of abundance and occupancy.encopepodsdistributionstrophic positiondissertation or thesishttps://doi.org/10.7298/6jbs-b342