Kowalko Lab

Johanna Kowalko Side Pics

Johanna Kowalko

Assistant Professor

Wilkes Honors College



Jupiter - MC-19, 207


  • Ph.D., Harvard University, 2013

Research Interests

  • Examining the genetic basis of and developmental changes that underlie complex trait evolution
  • Understanding how traits evolve repeatedly under similar environmental conditions
  • Developing genetic tools for examining cavefish evolution

Research Description

How does genetic variation, interpreted through developmental processes, contribute to phenotypic variation? How do the phenotypes that result from this variation contribute to relative fitness? My research program addresses these questions using the blind cavefish, Astyanax mexicanus. A. mexicanus exists in a river-dwelling surface form, as well as in multiple populations that have been trapped in, and have adapted to life in subterranean caves. Cavefish have adapted to survive and thrive in the cave environment through the modification of morphological, physiological and behavioral traits. While surface and cavefish have strikingly divergent phenotypes, they are interfertile, and are therefore a powerful genetic model of evolution. Furthermore, many of these cave populations have evolved from independent colonization events, allowing for the examination of repeated evolution. In addition, the small size, ability to live and breed in the laboratory, and short generation time of these fish make Astyanax an extraordinary system for genetic and developmental studies. These advantages, combined with the definable characteristics of the cave habitat under which these fish evolved, make Astyanax an extraordinary model system for studying the evolution of morphological and behavioral traits and their ecological significance. My research program leverages this model system to identify genes and genetic changes responsible for the evolution of organisms, to study the role these changes play at a functional level in generating complex traits and, ultimately, their effects on fitness.

Recent Publications

  • Tabin J.A., Aspiras A., Martineau B., Riddle M., Kowalko J.E., Borowsky R., Rohner N., Tabin C.J. (2018) Temperature preference of cave and surface populations of Astyanax mexicanus. Developmental Biology, 441(2): 338-344.
  • Klaassen H., Wang Y., Adamski K., Rohner N., Kowalko, J.E. (2018). CRISPR mutagenesis confirms the role of oca2 in melanin pigmentation in Astyanax mexicanus. Developmental Biology, 441(2): 313-318.
  • Kowalko J.E., Ma L., Jeffery W.R. (2016). Genome editing in Astyanax mexicanus using transcription activator-like effector nucleases (TALENs). Journal of visualized experiments: JoVE, (112).
  • Ma L., Jeffery W.R., Essner J.J., Kowalko J.E. (2015). Genome editing using TALENs in blind Mexican cavefish, Astyanax mexicanus. PLoS One, 10(3): e0119370.

Scholarly Activities

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 Last Modified 1/7/19