Meeting Abstract

86.5  Thursday, Jan. 7  Repeated patterns in the diversification of jaw and head length amongst perciform fishes COOPER, W.J.*; PARSONS, K.; WESTNEAT, M.W.; ALBERTSON, R.C.; Syracuse University; Syracuse University; The Field Museum; Syracuse University wjcooper@syr.edu

The skulls of perciform fishes have an anatomical configuration that permits their oral jaws to perform complex and dynamic movements, and this condition has frequently been linked to the massive evolutionary success of the group. We suggest that the perciform jaw mechanism may promote rapid evolutionary divergence due to the fact that simple changes in the morphology of this structure can have large ecological effects. Specifically, that altering the relative size of the preorbital region (which includes the oral jaws) can produce pronounced ecomorphological shifts. We have examined the functional morphology of fish feeding in multiple lineages that include a large percentage of the extant perciform species. Our results suggest that changes in the relative size of the preorbital region have been of extreme importance to the evolutionary success of these groups, and that such changes have often evolved with great speed. The alteration of oral jaw size has frequently been associated with diversification along a bentho-pelagic feeding axis, and is associated with divergence in bite force vs. bite speed. Our data suggest that this anatomical region may constitute an evolutionary module, and that changes in the size of this module may be under the control of a small number of genes of large effect. The Perciformes may therefore possess genetic and morphological arrangements such that simple genetic changes can rapidly produce important biomechanical and ecological shifts. This hypothesis has the potential to explain a large portion of the tremendous success of this group, which constitutes one of the largest branches of the vertebrata.