Year: 2016
Type: dissertation
Abstract: Evolutionary transitions between ecosystems are rare, and yet in lineages that have made these transitions we observe drastic changes in their diversity and richness as they adapt to novel habitats and novel resources. The main goal of my dissertation is to examine how transitions among diets and habitats have molded the evolution of predator traits. To test hypotheses regarding how prey materials have shaped the evolution of predators, I examined predator feeding biomechanics using experimental methods and deep-time approaches. Using 3D printing, computational milling, and computed tomography scanning, I compared the biomechanical performance of jaw shape for durophagous stingrays which prey on mollusks with shells of drastically different material and structural properties. I found that all of these jaw morphologies were equally well-suited to crushing the entire breadth of prey mollusk diversity, establishing equifinality of anatomical form stemming from convergent feeding mechanics. Insectivory has evolved only once within modern sharks and rays, found within the enigmatic freshwater stingrays of South America. Using high-speed videography and computed tomography scanning I found that these freshwater stingrays use chewing motions of the jaws when feeding on prey, facilitated by a highly kinetic cranial skeleton, and that these motions are exaggerated for tougher prey like insects. Loose jaw joints, transverse jaw kinesis, passive tooth reorientation, and a hydrodynamic tongue allow freshwater potamotrygonid rays to chew in a manner similar to many mammals. I investigated how the evolution of novel feeding modes such as insectivory and molluscivory in these freshwater rays has altered the tempo of their evolution by generating a molecular phylogeny for the family and analyzing feeding trait adaptation across 40 million years of evolution. The evolution of molluscivores and insectivores in this stingray clade are relatively modern innovations, coincident with the changing nature of the Amazon basin and repeated colonization of new riverine habitats. These dietary strategies, in addition to piscivory, are representative of truly novel adaptive peaks and have contributed to shifts in the rate of both lineage and morphological evolution in these remarkable freshwater stingrays.
Source: TSpace (University of Toronto)
Author: Matthew A. Kolmann
Language: English
Subfield: Nature and Landscape Conservation
Field: Environmental Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2623475554