UO paleontologist exploring dietary role in mammalian evolution

Mammalian paleontologist Samantha Hopkins is pursuing her research into the ways ancient dietary trends may have affected the diversity and evolution of mammals with a new grant from the National Science Foundation.

The three-year grant gives Hopkins and co-principal investigator Samantha Price, a postdoctoral researcher at the University of California, Davis, $389,667 to explore their ideas on diet of mammals over time.

The research focuses on three well-known and well-studied groups of mammals: Primates (monkeys and apes), Carnivora (dogs, cats and bears) and Cetartiodactyla (deer, cows and whales). Hopkins and her team will use morphological (physical characteristics such as shape and size) data as well as molecular data to synthesize new relationships and diversification rates among mammals.

"If you look at the patterns of relationships among mammals, and then paint diet onto that, what can you figure out about what mammals evolved?" said Hopkins, an assistant professor of paleontology in the University of Oregon's Robert D. Clark Honors College.

One of the specific methods Hopkins will use to investigate ancient diets is tooth morphology. In carnivore teeth, she can look at the size and shape of the carnassial, the largest of the back teeth in carnivores that were used for slicing and tearing. The size and shape of the blade on carnassial teeth determines how much meat an animal could eat. Hopkins will compare data from extinct mammal teeth to what is already known about the relationship between tooth morphology and diet in modern mammals.

"We're going to do a little more work to explore diet and dental morphology within the context of evolutionary history," Hopkins said. "Past studies have focused on the statistical correlation of diet and the physical characteristics of teeth."

To do this, she will be using both paleontological methods of research as well as methods in comparative evolutionary biology. Though the goals of both areas of research are discovering evolutionary relationships, subtle differences in analysis can arise that may foster disagreements. This is why Hopkins wants to use both approaches to get the most accurate results she can.

The idea has been with Hopkins since 2006, but couldn't fully pursue it until now. When Hopkins was working at the National Evolutionary Synthesis Center (NESCent), she and her colleagues started to think about how mammal diets can offer insights into their evolutionary relationships. NESCent is a NSF-funded nonprofit center dedicated to cross-disciplinary research in evolution and jointly operated by Duke University, the University of North Carolina at Chapel Hill and North Carolina State University.

Hopkins and her co-researchers compiled data from about one third of known mammals into a paper, published last year, in the Proceedings of the National Academy of Sciences. Herbivores, for example, diversify quickly because they are able to specialize based on their diet of plants, and plants are among the most diverse organisms. Omnivores, on the other hand, diversify more slowly because they are eating a little bit of everything and have little need for a specific diet. Carnivores are somewhere in between.

The only thing missing, Hopkins said, was the vast numbers of extinct species. Extinction is a response to environmental change, she said, and one of those environmental changes can involve whatever it is the extinct mammal was eating.

"We knew the paper wasn't the end answer to this. It's just that in order to incorporate fossils into this, we need to collect data that are harder to obtain, and, in fact, some of which didn't exist even a couple of years ago."

The NSF grant (No. 1256897) will allow Hopkins to investigate these questions more fully. Along with the fossil collection at the UO, Hopkins will travel around the country to look at collections at other institutes and museums. The grant will also allow Hopkins to hire undergraduate and graduate students to collect and analyze the new data on fossil and living mammals.

A requirement of an NSF grant is to make the research more widely applicable to the public. To do so, Hopkins and Price are working with the UO's Museum of Natural and Cultural History and the University of California, Berkeley, to develop teaching tools for teachers in kindergarten through the college undergraduate years. The goal is to develop a curriculum about the scientific process, which, Hopkins said, isn't emphasized in many science classes. There also will be an online component and physical exercises that teachers can lead in class.

"If there's no money for a small school to go on a field trip to a museum, teachers can at least go online and get some resources," Hopkins said.