Fish assemblage composition of the four basins of Wannan Mountains, China

Extensive distribution of widespread species and the loss of native
species driven by anthropogenic disturbances modify community similarity,
resulting in a decrease or increase in community distinctiveness. Data
from four basins in the Wannan Mountains, China, were used to evaluate the
effects of low-head dams on patterns of fish faunal homogenization and
differentiation based on abundance data. We aimed to examine the spatial
changes in taxonomic and functional similarities of fish assemblages
driven by low-head dams and whether the changes in the similarity of fish
assemblages differed between taxonomic and functional components. We found
that low-head dams significantly decreased the mean taxonomic similarity
but increased the mean functional similarity of fish assemblages in
impoundments using abundance-based approaches, suggesting that taxonomic
differentiation accompanied functional homogenization in stream fish
assemblages. These results show the importance of population abundance in
structuring fish faunal homogenization and differentiation at small
scales, especially when the major differences among assemblages are in
species abundance ranks rather than species identities. Additionally, we
also found only a weak positive correlation between changes in mean
taxonomic and functional similarities, and partial pairs exhibited
considerable variation in patterns of fish faunal homogenization and
differentiation for taxonomic and functional components. In conclusion,
this study highlighted that the observed taxonomic differentiation of
current fish assemblages (short-term phenomenon) is probably an early
warning sign of further homogenization in regions where native species are
completely predominated, and that changes in taxonomic similarity cannot
be used to predict changes in functional similarity. Keywords: Low-head
dam, Stream fish, Biotic homogenization and differentiation, Taxonomic and
functional diversities