Casey Dunn
Assistant Professor of Biology
Last March, the journal Nature published the most comprehensive animal evolutionary research to date. The work involved 40 million base pairs of new DNA taken from 29 animal species.
Casey Dunn led that study, which confirmed some existing relationships on Charles Darwin's Tree of Life and resolved some longstanding conflicts — finding, for example, that centipedes and millipedes are more closely related to arachnids than to insects.
“It used to be that to see if animals were related, you’d look for similarities in anatomy,” said Dunn. “For the last 20 years, you could pick a set of genes in advance, then sequence them. Now, you can randomly collect data and prepare a snapshot of the genes,” he said. “The tools I’m developing will tell you which are the best genes to look at, given certain relationships.”
Phylogenomics, the intersection of evolution and genomics, "is my excuse to work on all animals," Dunn said.
He uses all the tools available to him: “I'm as likely to use genomics from last week as I am a 150-year-old book,” he said.
He displayed a gift from a mentor, a dusty, doorstop-sized volume: Ernst Haeckel’s Report on the Siphonophorae Collected by H.M.S. Challenger During the Years 1873-1876. At the time, Haeckel was Darwin’s main advocate and one of the founders of evolutionary biology. Challenger’s 68,890 nautical-mile expedition has been called the birth of modern oceanography, providing proof of deep-sea life.
Dunn is one of the few scientists in the world who study siphonophores. The larger group of these creatures, the invertebrate phylum Cnidaria, includes colonial marine animals such as coral, anemones and box jellyfish.
The Portuguese-man-of-war is the best-known siphonore, because it lives at the ocean’s surface. Most of the other 175 species live in deep water; some are bioluminescent, glowing green or blue. Many had been undiscovered until Dunn found and documented them.
“Most biologists today haven’t even heard of siphonophones, but the earliest researchers recognized their importance,” Dunn said. Siphonophores are “the most extreme case of colony, with a higher degree of organization and precision of all colonial animals.
“It’s not widely known, but the colonies interact ... They’re like thousands of Siamese twins: Some only walk, some only feed, some only reproduce.”
Long, thin and gelatinous, siphonphores disintegrate when trawled with nets, so Dunn collects them by blue water diving (a deep-sea form of scuba), in manned submarines and remotely operated vehicles. “Field work, lab work and computational work are all very important to me,” he said.
His transition from research faculty to assistant professor has meant a widening of scope. “I can scale up now,” said Dunn, whose appointment is in the Department of Ecology and Evolutionary Biology. “I can work on everything that interests me, not just one section of it.”