Herein I study patterns of variation and their relationship to patterns of diversity in Neotropical electric fishes (Gymnotiformes: Teleostei). In Chapter I, I performed a taxonomic revision on a clade of deep channel electric-fishes (Sternarchella). In this revision, I described two new species and resolved taxonomic confusion about species identity in other taxa. In Chapter II, I performed a geometric morphometric analysis of gymnotiform skull shape. I integrated shape data with phylogenetic data to quantify the degree of convergent evolution within this clade. I found more instances of independent evolution towards short-snouted phenotypes than long-snouted phenotypes, and described a novel convergent phenotype. After identifying convergent craniofacial phenotypes, I tracked the neurocranial development and developmental integration of 17 species (363 specimens) that exhibited various convergent phenotypes. I found that the developmental trajectories were highly irregular for short-snouted species, while the long-snouted species exhibited more regular and consistent developmental patterns. I also found a significant relationship between developmental integration and adult skull shape. In Chapter III, I tracked the evolutionary integration of the face and braincase modules of the skull. I compared the gymnotiform and carnivoran patterns of neurocranial evolution and quantified the skulls’ ability to respond to selection pressures. I found that the carnivoran skull is modular and that this modularity allowed the braincase to exhibit significantly higher degrees of respondability to selection allowing it to evolve twice as fast as the face. In Gymnotiformes, I found that face and braincase were highly integrated and exhibited similar magnitudes of response to selection. This pattern of integration allowed for the similar rates of face and braincase shape evolution in this clade. In Chapter IV, I studied the trophic ecology of seven electric fish species that exhibit two types of brachycephalic skulls shapes, using stable isotopes and gut-content analyses to study the effect of developmental biases on the evolution of adaptive phenotypes. Using these data, I described four trophic guilds that did not cluster within the two skull shapes. This diversity in trophic ecologies associated with the conserved brachycephalic phenotypes suggests that the brachycephalic skull is widely adaptable for a variety of functions.
|Advisor:||Albert, James S.|
|Commitee:||France, Scott C., Moon, Brad R., Schubert, Brian A., Sidlauskas, Brian L.|
|School:||University of Louisiana at Lafayette|
|School Location:||United States -- Louisiana|
|Source:||DAI-B 79/09(E), Dissertation Abstracts International|
|Subjects:||Evolution and Development, Zoology|
|Keywords:||Craniofacial diversity, Evolution, Gymnotiformes: Teleostei, Neotropical electric fishes|
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