Host specificity of microsporidia: Physiological and ecological considerations
Solter, Leellen Felton
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Permalink
https://hdl.handle.net/2142/19925
Description
Title
Host specificity of microsporidia: Physiological and ecological considerations
Author(s)
Solter, Leellen Felton
Issue Date
1996
Doctoral Committee Chair(s)
Maddox, Joseph V.
Department of Study
Entomology
Discipline
Entomology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Biology, Ecology
Biology, Entomology
Agriculture, Forestry and Wildlife
Language
eng
Abstract
Results of traditional laboratory bioassays may not accurately represent ecological (field) host specificity of entomopathogens but, if carefully interpreted, may be used as a tool to predict ecological host specificity. I conducted two laboratory studies designed to predict the ecological host range of microsporidia, common protozoan pathogens of insects. In the first study, 49 nontarget lepidopteran species indigenous to North America were fed five biotypes of microsporidia which occur in European populations of Lymantria dispar but do not occur in North American populations of L. dispar. These microsporidia are candidates for release as classical biological control agents into L. dispar populations in the United States. The microsporidia produced a variety of responses in the nontarget hosts and, based on these responses, the nontarget hosts were placed in the following categories:(1) no infection, (2) atypical infections, and (3) heavy infections. Because most of the infections were not typical of infection in L. dispar, I predicted that four of the five microsporidian biotypes would not be horizontally transmitted within the nontarget insect populations. Because permission has not yet been granted to release all of these microsporidia into the field, it is not possible to evaluate ecological host specificity under field conditions. Therefore, I tested the predictive value of laboratory host range studies of microsporidia using a different concept for evaluating ecological host specificity. I considered L. dispar to be a potential nontarget host of microsporidia from indigenous North American insect species with which L. dispar overlaps ecologically. When fed purified viable spores, L. dispar was susceptible to nine biotypes of microsporidia from indigenous insect hosts and produced responses similar to those produced by L. dispar microsporidia in nontarget indigenous Lepidoptera. I then increased the complexity of the transmission experiments by exposing living uninfected L. dispar larvae in small cages to infected L. dispar larvae. Transmission of the microsporidia was greatly reduced or did not occur. Data sets from extensive pathogen surveys indicate that microsporidia do not occur in United States populations of L. dispar, validating the prediction that the physiological host range of microsporidia is broader than the ecological host range.
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