- Postdoctoral Fellow, Max Planck Institute for Developmental Biology, 2010-2014
- Ph.D., University of California, Riverside, 2009
Associate Professor, Biology
Associate Professor, Biology
Myers Hall 100
Ragsdale Lab website
Alexander von Humboldt Fellowship, 2011-2013
Erasmus Mundus Scholar, 2010
I study the role of developmental mechanisms in the evolution and diversification of form, using nematode worms as a tractable laboratory model. Nematodes lead virtually every lifestyle known to animals and include microbivores, omnivores, predators, and parasites of insects, vertebrates, and plants. The diversity of nematode mouthparts bears testament to this remarkable ability to specialize. I seek to unravel the mechanisms underlying such morphological diversification by integrating developmental genetics, phylogenetics, genomics, and natural history.
My lab uses the nematode Pristionchus pacificus as a reference point and model, and we focus on the genetics of developmental plasticity (polyphenism) in its mouthparts. After an irreversible decision in larval development, nematodes of this species, and others in its family (Diplogastridae), assume one of two distinct feeding-forms that perform alternative ecological functions. This dimorphism involves an evolutionary novelty: teeth, which enable predatory feeding on other nematodes.
Given the sometimes drastic influence that environment has on phenotypes, it is possible that developmental plasticity also plays a role in the evolution of such phenotypes, including novel traits. To question this possibility, my lab studies mouth plasticity in nematodes to identify the developmental program for executing a morphological novelty, and we are testing the significance of such a program in the evolution of plastic traits.
A few goals of this research include:
Specifically, my lab is using forward genetics to reconstruct the molecular pathway for a polyphenism switch and revealing how this switch has appeared and changed across lineages. Furthermore, we are using inference-based approaches, natural variation, and comparative reverse genetics to understand the evolution of these switch genes, the environmentally sensitive genes they regulate, and ultimately the novel phenotypes they influence.
Casasa, S., Katsougia, E., and Ragsdale, E.J. (2023). A Mediator subunit imparts robustness to a polyphenism decision. PNAS 120:e2308816120.
Harry, C.J., Messar, S.M., and Ragsdale, E.J. (2022). Comparative reconstruction of the predatory feeding structures of the polyphenic nematode Pristionchus pacificus. Evolution & Development 24:16–36.
Casasa, S., Biddle, J.F., Koutsovoulos, G.D., and Ragsdale, E.J. (2021). Polyphenism of a novel trait integrated rapidly evolving genes into ancestrally plastic networks. Molecular Biology and Evolution 38:331–343.
Biddle, J.F., and Ragsdale, E.J. (2020). Regulators of an ancient polyphenism evolved through episodic protein divergence and parallel gene radiations. Proceedings of the Royal Society of London B 287:20192595.
Bui, L.T., and Ragsdale, E.J. (2019). Multiple plasticity regulators reveal targets specifying an induced predatory form in nematodes. Molecular Biology and Evolution 36:2387–2399.
Ledón-Rettig, C.C., Moczek, A.P., and Ragsdale, E.J. (2018). Diplogastrellus nematodes are sexually transmitted mutualists that alter the bacterial and fungal communities of their beetle host. PNAS 115: 10696–10701.
Bui, L.T., Ivers, N.A., and Ragsdale, E.J. (2018). A sulfotransferase dosage-dependently regulates mouthpart polyphenism in the nematode Pristionchus pacificus. Nature Communications 9: 4119.
Kieninger, M. R., Ivers, N. A., Rödelsperger, C., Markov, G. V., Sommer, R. J., and Ragsdale, E. J. (2016). The nuclear hormone receptor NHR-40 acts downstream of the sulfatase EUD-1 as part of a developmental plasticity switch in Pristionchus. Current Biology 26: 1-6.