Egan, Joshua2020-11-172020-11-172019-08https://hdl.handle.net/11299/217133University of Minnesota Ph.D. dissertation. August 2019. Major: Fisheries. Advisor: Andrew Simons. 1 computer file (PDF); vii, 183 pages.The increase in species richness from the poles to the equator is one of the most pervasive and enigmatic spatial patterns of biodiversity. This latitudinal diversity gradient has been intensively studied since it was first described in 1807 and yet there is still no accepted explanation for its existence. My dissertation tested hypotheses about the origins of the latitudinal diversity gradient in the ecologically and economically important clupeiform fishes (anchovies, sardines, and relatives) with a focus on the hypothesized role of niche breadth evolution in the formation of the diversity gradient. My first chapter described the diets of near-shore, marine clupeiforms from Taiwan and compared their diets to co-occurring fish species. My second dissertation chapter identified increasing ranges of prey-size consumption through ontogeny in twelve species of Indo-Pacific clupeiforms. For my third dissertation chapter, I inferred a time-calibrated clupeiform phylogeny and patterns of diet evolution, which revealed a latitudinal herbivory gradient in clupeiforms. My fourth dissertation chapter found support for climate niche conservatism in the origins of the latitudinal diversity gradient in clupeiforms using diet data from chapter one, two, and three and the phylogeny from chapter three. My dissertation research contributes to the development of biological theory and efforts to sustainably manage fisheries.enAnchovyDiversification rateDiversity gradientEcological nicheHerringSardineThesis or Dissertation