Emergent Fungal Entomopathogen Does Not Alter Density Dependence in a Viral Competitor

Population cycles in forest Lepidoptera often result from recurring density-dependent epizootics of entomopathogens. While these systems are typically dominated by a single pathogen species, insects are often infected by multiple pathogens, yet little is known how pathogens interact to affect host dynamics. The apparent invasion of northeastern North America by the fungal entomopathogen Entomophaga maimaiga some time prior to 1989 provides a unique opportunity to evaluate such interactions. Prior to the arrival of E. maimaga, the oscillatory dynamics of host gypsy moth, Lymantria dispar, populations were apparently driven by epizootics of a nucleopolyhedrovirus. Subsequent to its emergence, E. maimaiga has caused extensive mortality in host populations, but little is known about how it has altered multigenerational dynamics of the gypsy moth and its virus. Here we compared demographic data collected in gypsy moth populations prior to vs. after E. maimaiga\u27s invasion. We found that the recently invading fungal pathogen virtually always causes greater levels of mortality in hosts than does the virus, but fungal mortality is largely density independent. Moreover, the presence of the fungus has apparently not altered the gypsy moth–virus density-dependent interactions that were shown to drive periodic oscillations in hosts before the arrival of the fungus

Impact of Entomophaga maimaiga

The fungal pathogen Entomophaga maimaiga Humber, Shimazu, and Soper is prevalent in gypsy moth [Lymantria dispar (L.)] populations throughout North America. To understand how weather-related variables influence gypsy moth-E. maimaiga interactions in the field, we measured fungal infection rates at 12 sites in central Pennsylvania over 3 yr, concurrently measuring rainfall, soil moisture, humidity, and temperature. Fungal mortality was assessed using both field-collected larvae and laboratory-reared larvae caged on the forest floor. We found significant positive effects of moisture-related variables (rainfall, soil moisture, and relative humidity) on mortality due to fungal infection in both data sets, and significant negative effects of temperature on the mortality of field-collected larvae. Lack of a clear temperature relationship with the mortality of caged larvae may be attributable to differential initiation of infection by resting spores and conidia or to microclimate effects. These relationships may be helpful in understanding how gypsy moth dynamics vary across space and time, and in forecasting how the gypsy moth and fungus will interact as they move into warmer or drier areas, or new weather conditions occur due to climate change

Spectral induced polarization signatures of microbial nitrate reduction in unsaturated sediment columns

This file contains the SIP spectra data of nitrate bioreduction experiments promoted by Shewanella oneidensis strain MR-1 (Exp. 1-3) in unsaturated coarse H2C and fine H2F Hanford sediments. The data are sorted by the phase angle (mrads), quadrature (imaginary) and in-phase (real) conductivity (mS/m)

Impact of Entomophaga maimaiga (Entomophthorales: Entomophthoraceae) on Outbreak Gypsy Moth Populations (Lepidoptera: Erebidae): The Role of Weather

The fungal pathogen Entomophaga maimaiga Humber, Shimazu, and Soper is prevalent in gypsy moth [Lymantria dispar (L.)] populations throughout North America. To understand how weather-related variables influence gypsy moth-E. maimaiga interactions in the field, we measured fungal infection rates at 12 sites in central Pennsylvania over 3 yr, concurrently measuring rainfall, soil moisture, humidity, and temperature. Fungal mortality was assessed using both field-collected larvae and laboratory-reared larvae caged on the forest floor. We found significant positive effects of moisture-related variables (rainfall, soil moisture, and relative humidity) on mortality due to fungal infection in both data sets, and significant negative effects of temperature on the mortality of field-collected larvae. Lack of a clear temperature relationship with the mortality of caged larvae may be attributable to differential initiation of infection by resting spores and conidia or to microclimate effects. These relationships may be helpful in understanding how gypsy moth dynamics vary across space and time, and in forecasting how the gypsy moth and fungus will interact as they move into warmer or drier areas, or new weather conditions occur due to climate change

Reduction of TcO4- by sediment-associated biogenic Fe(II)

The potential for reduction of 99TcO4-(aq) to poorly soluble 99TcO2 · nH2O(s) by biogenic sediment-associated Fe(II) was investigated with three Fe(III)-oxide containing subsurface materials and the dissimilatory metal-reducing subsurface bacterium Shewanella putrefaciens CN32. Two of the subsurface materials from the U.S. Department of Energy’s Hanford and Oak Ridge sites contained significant amounts of Mn(III,IV) oxides and net bioreduction of Fe(III) to Fe(II) was not observed until essentially all of the hydroxylamine HCl-extractable Mn was reduced. In anoxic, unreduced sediment or where Mn oxide bioreduction was incomplete, exogenous biogenic TcO2 · nH2O(s) was slowly oxidized over a period of weeks. Subsurface materials that were bioreduced to varying degrees and then pasteurized to eliminate biological activity, reduced TcO-4(aq) at rates that generally increased with increasing concentrations of 0.5 N HClextractable Fe(II). Two of the sediments showed a common relationship between extractable Fe(II) concentration (in mM) and the first-order reduction rate (in h-1), whereas the third demonstrated a markedly different trend. A combination of chemical extractions and 57Fe Mossbauer spectroscopy were used to characterize the Fe(III) and Fe(II) phases. There was little evidence of the formation of secondary Fe (II) biominerals as a result of bioreduction, suggesting that the reactive forms of Fe(II) were predominantly surface complexes of different forms. The reduction rates of Tc (VII)O-4 were slowest in the sediment that contained plentiful layer silicates (illite, vermiculite, and smectite), suggesting that Fe(II) sorption complexes on these phases were least reactive toward pertechnetate. These results suggest that the in situmicrobial reduction of sediment associated Fe(III), either naturally or via redox manipulation, may be effective at immobilizing TcO4- (aq) associated with groundwater contaminant plumes

Appendix A. A description of the study sites.

A description of the study sites

Appendix B. Numbers of gypsy moth larvae collected.

Numbers of gypsy moth larvae collected

Supplement 1. SAS code for general linear model analysis.

<h2>File List</h2><div> <p><a href="glm.sas">glm.sas</a> (MD5: c946a1840dd18caadcf2dfc663ab664e) </p> </div><h2>Description</h2><div> <p>The file glm.sas contains SAS code for testing the significance of differences in the linear relationship of season-long LdNPV mortality to log10 egg mass density collected before and after 1989 (the point at which <i>E. maimaiga</i> appeared in North American gypsy moth populations).</p> </div