Bats evolved diverse skull shapes due to echolocation, diet

Humans may be forgiven for overlooking bats. After all, many bat species are out and about when we're turning in. And generations of Dracula lore may have made us a little wary. But bats are a diverse bunch. They make up one of the largest groups of mammals, with more than 1,300 species worldwide. Up close, bat species look quite different from one another. Some have large ears. Others sport elaborate noses or long jaws. With so much morphological variety, bats represent an opportunity to learn what types of evolutionary forces shape the shapes of animals. A team of biologists at the University of Washington has been using bats to do just that. Postdoctoral researchers Jessica Arbour and Abigail Curtis, and Sharlene Santana, UW associate professor of biology and curator of mammals at the UW's Burke Museum of Natural History & Culture, focused on the diversity among bat skulls. The researchers performed high-resolution microCT scans of the skulls of more than 200 bat species. They used the scans, as well as information on the evolutionary relationships among bat species, to analyze the types of physical changes that evolved in bat skulls over tens of millions of years and correlate them with specific events in bat evolution, such as when a lineage switched diets or adapted to a new ecological niche. In a paper published May 2 in Nature Communications, they report that two major forces have shaped bat skulls over their evolutionary history: echolocation and diet. They were even able to determine when in bat history these forces were dominant.