Looking Similar But Structured Differently: Decoupling Taxonomic and Functional Diversity From Trophic Diversity Amongst Freshwater Fish Communities

ABSTRACT: Despite intensive research studying how biodiversity relates to ecosystems structure and functioning during the past 30 years, our ability to mechanistically explain how species composition influences communities’ trophic structure remains insufficient. To better understand the complex relationship between taxonomic, functional, and trophic diversity we collected trait and stable isotope data from the primary literature for 63 fish communities occurring throughout North America. Each community’s taxonomic, functional, and trophic diversity (alpha diversity) was quantified along with their pairwise similarity (beta diversity) to determine if fish communities trophic similarity was correlated with their taxonomic or functional similarity. We found that while individual communities’ taxonomic and functional diversity was positively associated with their trophic diversity, the taxonomic and functional similarity of community pairs was a poor predictor of their trophic similarity. Our results suggest that context dependent factors, in addition to the taxonomic and functional diversity of fish communities, strongly influence the trophic structure of freshwater communities.