Beta Diversity of Stream Fish Communities: Partitioning Variation Between Abiotic and Spatial Factors

Abstract

Variation in species composition of assemblages within a region is known as beta diversity. Beta diversity contributes to regional diversity (gamma), and understanding the factors that maintain it and explain variation of it are necessary for conserving biodiversity. I examined beta diversity among stream fish communities in southeastern Oklahoma to test the hypothesis that beta diversity was driven by abiotic factors and therefore was under environmental control. I used variation partitioning via redundancy analysis to analyze the proportions of beta diversity explained by abiotic and spatial factors. I also computed total species turnover and its components of spatial turnover and nestedness, for the region and within groups. I then related turnover distance matrices to environmental and spatial distances via a Mantel approach. Environmental factors accounted for 28% of the overall beta diversity, and abiotic factors and spatial factors alone accounted for 25% and 3% respectively. Abiotic factors related to beta diversity were stream size, habitat, water quality, and position within the drainage. Overall species turnover was mostly due to spatial turnover, and much less to nestedness. Variation in overall species turnover and spatial turnover were both significantly related to variation in environment and physical distance, while nestedness was not.