SIDLAUSKAS, B.L.; University of Chicago / The Field Museum: Morphological diversification of anostomid and curimatid fishes

My research takes advantage of a rare natural experiment to investigate how and why species in the South American freshwater fish family Anostomidae have evolved a diversity of head and jaw shapes that greatly exceeds that of the closely related, sympatric and equally species-rich Curimatidae. Using a multivariate morphological space (morphospace) derived from the geometry of anostomid and curimatid skulls, I calculate the morphological diversity (disparity) of each family and address the evolution of morphological diversity along a phylogeny. Anostomid morphological diversity is measurably higher than that of curimatids, and the increased morphological diversity in anostomids appears to be relatively ancient. Though both families attained much of their current morphological diversity early in phylogenesis, the Curimatidae appear to have experienced an early saturation of morphological space while the Anostomidae continued to evolve novel morphologies and occupy new morphospace regions. This study will help identify uniquely derived morphological and ecological factors that may have promoted morphological diversification and help explain why morphological diversity is distributed unevenly across the tree of life.