Continental-scale analysis of taxonomic and functional fish diversity in the Yangtze river

Effective conservation of ecosystems requires deep knowledge concerning multiple aspects of biodiversity including alpha and beta components of species richness, taxonomic, and functional diversity, as well as their relationships. The taxonomic and functional α-diversity positively correlated to species richness and functional evolution exceeded taxonomic differentiation. We divided the Yangtze whole basin into 56 units, and then the information on fish composition and their distribution in each unit was revised. Results showed that the fish diversity was strongly driven by variation in the species turnover between watersheds with the geological environmental heterogeneity, while the TD and FD variation could be attributed to species nestedness, as taxonomic category or functional trait of species in one unit was a subset of that in other units. The high β-diversity in SR was mostly composed of high turnover, while the high β-diversity of TD and FD resulted from high nestedness. Species functional differentiation was faster than taxonomic differentiation during the process of adoption to environment variation. An integrated index of multifaceted diversity considering the high species richness and important functional role suggested the headwater with abundant endemic species, the middle mainstream necessary to fish migration, and the lakes containing higher diverse species were primarily recommended for conservation.