NSF Postdoctoral Fellowship in Biology FY 2019: Mammals in the water: the loss of mastication in marine carnivores

Peredo Carlos M, Laurel MD

Investigators

Abstract

This action funds an NSF Postdoctoral Research Fellowship in Biology for FY 2019, Broadening Participation of Groups Under-represented in Biology. The fellowship supports a research and training plan for the Fellow that will increase the participation of groups underrepresented in biology. Marine mammals represent textbook examples of the fossil record documenting major physical transformations driven by changing ecology through time. To facilitate their transition from life on land to in the water, marine mammals undergo major shifts in feeding strategies. Carnivorous marine mammals lack the specialized molars adapted for chewing: a hallmark of land mammals. Instead, they have reduced or absent teeth. Does the return to a marine environment select for a reduction and loss of dentition in carnivorous mammals? Is chewing inefficient or ineffective for underwater feeding? This project will study feeding examples across the land to sea transition for carnivorous mammals to understand how changes in environment drive changes in dentition. The fellow will work with the University of Michigan Museum of Paleontology to showcase feeding diversity in marine mammals. The fellow will mentor students from underrepresented groups and produce bilingual educational materials for teaching the evolution of marine feeding. Mammals returning to the ocean undergo dramatic morphological changes akin to scales to feathers in dinosaurs and fins to limbs in tetrapods. This research addresses large-scale questions about selective pressures on mammalian feeding systems and will identify the ecological drivers behind the loss of mastication: a critical precursor to more specialized feeding strategies (suction, piercing, and filter-feeding). This study will: perform shape analyses of teeth to quantify the diversity of dental phenotypes and identify instances of simplification (objective-1); conduct puncture tests to measure the performance of specific dental morphologies (objective-2); and place these results in an evolutionary context using time calibrated phylogenetic analyses (objective-3). It will test the following hypotheses: (H1) cetaceans and pinnipeds converge on overlapping dental phenotypes; (H2) both clades independently simplify and reduce their dentition through time; (H3) each dental phenotype is capable of effective mastication; (H4) the loss of mastication is temporally linked to the reduction and/or simplification of teeth; and (H5) the loss of mastication is an evolutionary adaptation for marine feeding. This research will integrate fossil and modern data to link specific morphologies to ecological performance, which is critical to understanding the evolution of complex structures from simple elements. The fellow will mentor students from underrepresented groups and produce bilingual educational materials for teaching the evolution of marine feeding. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.