Meeting Abstract
Spatial patterns of beta diversity (turnover and nestedness) provide insight into how fish communities respond to environmental gradients and human disturbances (e.g. urbanization, and impoundments). Here, we used historical (1977-1982) and current (2016-2017) fish community data from the Saline River basin and Ouachita River basin, Arkansas to examine patterns of beta diversity and spatial structure at three spatial scales: entire river network, mainstem, and tributaries. Specifically, we investigated the increase of pairwise community dissimilarity (i.e. distance decay of similarity) with watercourse distance (rkm). In the Saline River network, we found spatial structure was consistent through time. Overall beta diversity (βsor) and species turnover (βsim) was positively correlated with watercourse distance at all spatial scales and nestedness (βnes) did not correlate with watercourse distance. Species turnover was stronger in tributaries than the mainstem because of high environmental heterogeneity. In the Ouachita River network, we found spatial structure changed through time. Overall beta diversity (βsor) and βsim was lower at all spatial scales during the current period, suggesting the breakdown of regional distinctiveness. Our results show that stream networks influence metacommunity structure, but also demonstrate human disturbances can disrupt natural structuring mechanisms and transform spatial structure in altered stream networks.
