CEB Committe on Evolutionary Biology

Welcome to CEB!

The Committee on Evolutionary Biology (CEB) is a unique interdepartmental and inter-institutional graduate student training program dedicated to the study of Evolutionary Biology. Faculty and students in the program are engaged in interdisciplinary studies at time scales that range from single generations to the entire history of life and at organizational scales from the molecular to the global.

Tim Sosa

Tim carrying a bucket of fish out of a creek bed in Sacatepequez, Guatemala. 


Tim Sosa

I study how freshwater animals invade new territories over time. I use DNA to reconstruct their ancestry (molecular phylogenetics), and with knowledge of their ancestry, I try to identify routes of colonization (phylogeography), timing of colonization events (historical biogeography), and trends in morphological evolution (geometric morphometrics). Right now I'm working with a group of freshwater fishes called Characiformes, which includes some familiar fish like neon tetras, freshwater hatchetfishes, and piranhas. Altogether, there are around 1,700 known species, mostly in South America and Africa. However, several lineages invaded North America 3-7 million years ago, after Panama joined North and South America together after a long separation dating back to the Jurassic period. The colonization of North America by tetras was part of a major event called the Great American Interchange, which also gave North America opossums, porcupines, and armadillos, and gave South America camels, deer, and foxes.

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