P1-102 - Evolutionary patterns of marine mammal feeding strategies Thomas, J*; Adams, D; Price, S; Clemson University; Clemson University; Clemson University email@example.com
Two competing hypotheses explain the evolution of feeding strategy in marine mammals. The first proposes an evolutionary continuum leading from terrestrial to specialized aquatic feeding, while the second suggests a branching pattern of evolution that does not have a stepwise progression. We tested these evolutionary hypotheses by collecting feeding strategy data on 113 species from the literature; categorizing species as either; (1) aquatic raptorial, (2) suction, (3) suction filter, or (4) ram filter. Toothed whales and pinnipeds utilized aquatic raptorial and suction feeding, while most baleen whales were categorized as ram filter feeders. Only two extant species used suction filter feeding. To analyze evolutionary transitions we determined the best fitting evolutionary model and performed stochastic character mapping. As pinnipeds & cetaceans had differing best fitting models, the stochastic character reconstructions were performed separately. The results suggested possible stepwise evolution of foraging strategy for pinnipeds, but not cetaceans. Summaries of character reconstructions showed multiple transitions between aquatic raptorial and suction feeders, and low posterior probability of suction filter as the ancestral state. This is inconsistent with the evolutionary continuum hypothesis, as suction filter feeding does not appear in its hypothesized sequential step between suction and ram filter feeding. However, because suction filter feeding is rare in living species, it might be a transition state that only appears in the fossil record. Alternatively, suction filter feeding could be a foraging strategy that only evolved recently, which would suggest that foraging evolution does not follow a sequential pattern. Although we found little support for sequential evolution, incorporating fossil data will provide a more complete understanding of the evolution of marine mammal foraging strategies.