Location: Emerging Pests and Pathogens ResearchTitle: Sequential utilization of hosts from different fly families by genetically distinct, sympatric populations within the Entomophthora muscae species complex Author
Submitted to: PLoS One
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/2013
Publication Date: 8/8/2013
Citation: Gryganskyi, A., Humber, R.A., Stajich, J., Mullens, B., Anishchenko, I., Vilgalys, R. 2013. Sequential utilization of hosts from different fly families by genetically distinct, sympatric populations within the Entomophthora muscae species complex. PLoS One. DOI: 10.1371/journal.pone.0071168. Interpretive Summary: A two-year study of fly populations in Durham, NC, and its interaction with the fungal pathogen Entomophthora muscae indicated an unexpected shift in both years: The fungus initially affected plant-feeding flies (Delia radicum) in the early spring, but then appeared to shift from the middle to later spring to affect only predatory flies (Coenosia sp.) that preyed upon the populations of Delia radicum. The identity of the fungus was studied by both traditional and genotypic characters, and demonstrated a very slight but reproducible genetypic shift in the fungus during the season. This is a highly unusual study for following a single fungal pathogen and its affected host populations throughout a season on a set of sites representing a single habitat type. This study should be useful for further ecological studies of these fungi, in helping to understand how the fungal pathogen, Entomophthora muscae (and, possibly, other closely related species in this genus) may be more effectively used as a biological control agent. The study raises questions about possible changes in genotypes of the populations of a fungal pathogen as it changes among populations of susceptible hosts.
Technical Abstract: Dynamics of infection were described for Entomophthora muscae (Entomophthoromycota, Entomophthorales, Entomophthoraceae) from the plant feeding fly Delia radicum and the predatory fly Coenosia tigrina, their primary and secondary hosts, respectively. Populations of these infected flies were sampled in 2011-2012 in Durham, North Carolina, USA. Infections first appeared in the middle of March on Delia and continued by utilizing a rapidly increasing proportion of Coenosia through time. By the end of May, Coenosia comprised 100 percent of sampled infected hosts. Optimal conditions for fungal infection were: average temperature 11-28 degC, dew point 3-21 degC, and rain 1-3 days before sampling. Occurrence of infected flies is correlated moderately well with average temperature, lowest temperature, and dew point (r = 0.33, 0.36 and 0.33 respectively) and is weakly correlated (r = 0.14) with relative humidity. The fungus developed inside infected flies as with rounded to rod-shaped multinucleate hyphal bodies, 6-25 x 4-18 micromolar. The simple conidiophores bore campanulate primary conidia 18-25 x 18-20 micromolar with a length/diameter ratio 1.16-1.3. Conidia contained 7-17 (average 12) nuclei, with a somewhat pointed (apiculate) apex and broad, flat basal papilla. Secondary conidia were similar in shape to the primary conidia but smaller (18-24 x 15-19 micromolar) and usually with a rounded (nonapiculate) apex. Collected specimens were genotypically close to E. muscae and E. scatophagae but differed morphologically and karyologically. This suggests the broader range of these characteristics may occur in the still incompletely resolved E. muscae species complex. Results illustrate the complexity of insect-fungus relationships in this ecosystem and should be considered for the development of biological control methods.