Hydrogeomorphic drivers of functional diversity in riverine fishes at an intercontinental scale

Abstract

Functional diversity (FD) has been used as a metric to gauge the health and stability of fish communities in many different environments, but few studies have examined FD on an intercontinental scale. This study formally examined the FD of riverine fishes at a macrosystem scale based on hydrogeomorphic features in similar climates between two continents. To accomplish this goal, I sampled fish in five systems representing three ecoregions (terminal basin, mountain steppe and grasslands) across the United States of America and Mongolia. I then investigated how FD changed between and within each continent and ecoregion type. As expected, FD was strongly correlated with species diversity. Additionally, I found that FD, specifically functional richness, was higher in wider, deeper rivers and decreased with faster, more sloped systems. This suggests that FD increases similarly to species richness as one moves from high elevation headwaters toward larger, lowland systems. However, a community containing redundant species that offer no novel traits to the community can complicate this generality. This project should serve as a complement to earlier work as well as provide a foundation for future studies that attempt to more thoroughly understand functional diversity at a macrosystem scale.