Functional groupings of stream fishes: Spatiotemporal variation, predictability, and patterns of diversity



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Biodiversity and ecosystem function is a contemporary topic at the forefront of ecology. It is driven by the fundamental need to understand how the loss of biodiversity, which is occurring all around the world, affects goods and services obtained from ecosystems. The scientific literature indicates functional attributes of species strongly influence ecosystem properties; however, a lack of understanding exists regarding the relationship among functional diversity, taxonomic diversity, and community structure. As a result, this dissertation contributes to our understanding of the relationship between biodiversity and ecosystem function by analyzing the organization of stream-fish assemblages from a functional and taxonomic perspective and by synthesizing the relationship between the two aspects of biodiversity. I used a combination of previously published data, which covered broad biogeographic areas, and my own field work to address various issues on multiple spatial and temporal scales. I focused exclusively on stream-fish assemblages because they are one of the most underrepresented groups of animals in biodiversity and ecosystem function research and because they play an important role in aquatic ecosystems by removing other plants and animals from the community, actively produce fragments or feces containing the bodies of their prey, and by mechanically disturbing substrates, thereby increasing suspension of materials in the water column. In general, I found functional redundancy within stream-fish assemblages, with functional groups dividing niche space more evenly than species whether looking at the entire state, ecoregions, river basins, or individual locations, and the spatial and temporal structure of stream-fish assemblages is similar for functional and taxonomic perspectives. These results indicate the need for future studies on biodiversity and ecosystem function to explicitly examine functional diversity, or at least incorporate functional attributes of individuals, in order to gain a holistic understanding.