Research focus

Research interests are in the systematics and evolution of nematodes. Focus has been on the evolution of feeding structures of Tylenchomorpha, a group that includes most plant parasitic nematodes. Although differences between these nematodes and their closest freeliving (i.e. bacterial feeding) outgroups are sharp, closer examination of relevant characters sheds light on transformations. To test hypotheses of homology, characters are mapped on phylogenetic trees based on independent morphological and molecular data. A comparative understanding of feeding apparati, including the stoma/stylet and the pharynx, has implications for the evolution of plant parasitism. Other morphological characters, such as those of the sensory system, are studied using techniques including electron microscopy and 3D reconstruction of individual cells. Reconstructed anatomy, with reference to the model nematode Caenorhabditis elegans, also provides a basis for expanding functional systems research. To develop a phylogenetic framework for hypotheses of evolution, novel molecular sequence data are being explored for analysis.

Degrees

B.S. Biology, B.A. History; University of California, Riverside, 2003
Ph.D. Entomology; University of California, Riverside, 2009

Recent Publications

Ragsdale, E. J., Ngo, P. T., Crum, J., Ellisman, M. H., and J. G. Baldwin. In press. Reconstruction of the pharyngeal corpus of Aphelenchus avenae (Nematoda: Tylenchomorpha), with implications for phylogenetic congruence. Zoological Journal of the Linnean Society.

Giblin-Davis, R. M., Kanzaki, N., De Ley, P., Williams, D. S., Schierenberg, E., Ragsdale, E. J., Zeng Y., and B. J. Center. In press. Ultrastructure and life history of Myolaimus byersi n. sp. (Myolaimina: Myolaimidae); a phoretic associate of the crane fly Limonia schwarzi (Alexander) (Limoniidae) in Florida. Nematology.

Ragsdale, E. J., Ngo, P. T., Crum, J., Ellisman, M. H., and J. G. Baldwin. 2009. Comparative, three-dimensional anterior sensory reconstruction of Aphelenchus avenae (Nematoda: Tylenchomorpha). Journal of Comparative Neurology. 517: 616-632.

Ragsdale, E. J., Crum, J., Ellisman, M. H., and J. G. Baldwin. 2008. Three-dimensional reconstruction of the stomatostylet and anterior epidermis in the nematode Aphelenchus avenae (Nematoda: Aphelenchidae) with implications for the evolution of plant parasitism. Journal of Morphology 269: 1181-1196.

Subbotin, S. A., Ragsdale, E. J., Mullens, T., Roberts, P. A., Mundo-Ocampo, M., and J. G. Baldwin. 2008. A phylogenetic framework for root lesion nematodes of the genus Pratylenchus (Nematoda): evidence from 18S and D2-D3 expansion segments of 28S ribosomal RNA genes and morphological characters. Molecular Phylogenetics and Evolution 48: 491-505.

Baldwin, J. G., Ragsdale, E. J., and D. Bumbarger. 2004. Revised hypotheses for phylogenetic homology of the stomatostylet in tylenchid nematodes. Nematology 6: 623-632.