SIDLAUSKAS, B. L.; CHERNOFF, B.; MACHADO-ALLISON, A.; University of Chicago and The Field Museum, Chicago, IL; University of Chicago and The Field Museum, Chicago, IL; Universidad Central de Venezuela, Caracas: Geographic and environmental variation in Bryconops cf. melanurus (Ostariophysi: Characidae) from the Brazilian Pantanal

Morphometric analyses of 220 specimens of Bryconops cf. melanurus from the Brazilian Pantanal demonstrated that specimens from highland stream populations are more streamlined than those from lowland habitats. Relative warp analysis of 14 landmarks and principal component analysis of 28 interlandmark distances returned complementary results. Because the observed streamlining is consistent with effects of high water velocity on fish phenotypes, and because highland streams in the Pantanal are typically swifter than lowland streams, we propose variation in water velocity as the most likely elevational correlate and source of phenotypic variation.