Hughes Mentor:  Amy McCune

Department: Ecology and Evolutionary Biology

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Professor Amy McCune

Some scientists have it easy. The benefit of studying cell division in cancer cells or finding ways to increase crop yield are so apparent that scientists in those fields aren’t ever asked defend their interests. Evolutionary biologists, in general, are not that lucky. Knowing all there is to know about speciation in fish is not going to cure any diseases soon, and it won’t rid agriculture of pests; but that doesn’t bother Amy McCune.

McCune is a professor in the Department of Ecology and Evolutionary Biology at Cornell, and also is the Faculty Curator of Fishes at the Cornell Museum of Vertebrates. She says she believes that people become researchers “not because of the application of the work, but because they love the questions.” For Professor McCune the questions are about how new species arise, the evolution of an organism’s traits, and the origin of variation. She researches these questions by studying fossilized and contemporary fish.

As a doctorial student McCune planned to do her PhD on how a species could split into separate species, a process called speciation. Particularly, she wanted to learn about adaptive radiation, a process where one species gives rise to many new species in a short amount of time. To investigate this she planned on looking at the Cichlids of Lake Malawi, a family of fish that dominate the lake. All of the more than 450 species are thought to be descendents of one or a few original species that colonized the lake, which would have been good case of adaptive radiation for her to study.

Before long though, McCune realized that studying the Cichlids of present day Lake Malawi was studying the products of evolution, and what she wanted to do was study the process in action. To do this she chose a family of fish that had speciated similarly to the Cichlids, called Semionotoids, which lived 185 to 210 million years ago in lakes spread from present day North Carolina to Nova Scotia. The well-preserved fossil record of these fish document the changes that took place in Semionotoids over millions of years. By examining fossils from the ancient lakebeds of different lakes, and from different time periods, she could look for patterns of change.

More recently McCune has looked at the genetic causes of the origin of variation in zebrafish. Following her interest in diversity within a species she looked for the number and type of recessive lethal mutations a wild zebrafish has. A recessive lethal mutation is a mutation that is lethal when paired with another like it, but does not cause the organism to die when present in only one copy. She found that a zebrafish carried on average one recessive lethal mutation, and she found a total of 27 different types. But McCune found something else as well. In at least 19 of those cases, carrying only one copy of those mutations, while not causing death, caused a severe physical abnormality in the fish. This abnormality was the loss of the swim bladder, an organ used as buoyancy device in many fish. This organ may also be the evolutionary related to lungs. Now that McCune has identified some of the genes contributing to swim bladder formation, she wants to see if they are involved in lung formation as well.

Who knows, she might discover a cause of a human genetic lung disease yet.

But even if she doesn’t, by investigating how species change, McCune will have expanded our knowledge of why the world is like it is. She will have done it by always following the questions that most interested her. If young scientists are looking for advice, they should follow the questions that most interest them.