Movement of Adult Colorado Potato Beetles, \u3ci\u3eLeptinotarsa Decemlineata\u3c/i\u3e (Coleoptera: Chrysomelidae), in Response to Isolated Potato Plots

Mark recapture techniques were used to determine Colorado potato beetle movement in circular arenas with isolated plots of potatoes at each ordinal direction. Post-diapause beetles aggregated on one or a few of the plants in one of the plots for each release, but not on the same plants in different releases. Differences in plant attractiveness were therefore not likely responsible for the aggregatory behavior. Aggregations were probably a result of either coordinated movement from the release site to the plants or an aggregatory signal with a range of at least 15 m. Summer adults did not aggregate on plants. Correlations of summer beetle recapture distributions to wind direction showed that anemotactic behavior could not account for the major portion of variation in beetle orientation to the potato plots. Some positive attraction to the plots was indicated because more beetles were recaptured at the plots than would be expected from random motion. The number of beetles recaptured at plots covered by cheesecloth was not significantly different from recaptures on uncovered plots, indicating little reliance on visual cues specific to potatoes for location of the plants

Marking Adult Colorado Potato Beetles, \u3ci\u3eLeptinotarsa Decemlineata\u3c/i\u3e (Coleoptera: Chrysomelidae) Using Paper Labels

The smooth elytra of adult Colorado potato beetle, Leptinotarsa decemlineata, make this insect difficult to make efficiently for long-term field studies. Enamel paint marks fell off rapidly, and after 28 days, 25010 of marked beetles had lost all four original marks. Use of small paper labels glued to the elytra after an acetone wash and sanding pretreatment was the most effective method for long term marking of individual beetles. Mortality in labeled laboratory-reared and field-collected beetles did not increase when compared to unmarked beetles

Evaluating the impacts of refuge width on source-sink dynamics between transgenic and non-transgenic cotton

Resistance management for Bt-transgenic crops relies in part on the production of sufficient numbers of susceptible insects in non-toxic refuges. Simulation models suggested that source-sink dynamics could interact with the structure of refuges to impact the production of insects in these areas. We tested the hypothesis that altering isolation between refuges and transgenic cotton by manipulating the width of refuges embedded within cotton fields would alter the density of Heliothis virescens and Helicoverpa zea eggs oviposited in refuges. Three categories of refuge widths were tested over two years: they included narrow (16–24m wide), medium (32-48m wide) and wide (80–96m wide) refuges. Isolation between the two habitats increased as refuge width increased. In 1996, eggs of H. virescens from H. zea were not distinguished, but a significant increase in the density of eggs and a significant decrease in relative yield (refuge yield compared to the yield from immediately surrounding Bt-cotton) was found as refuge width increased. In 1997, eggs from H. virescens were analyzed separately from H. zea using an ELISA test. The density of H. virescens eggs increased with increasing refuge width, and there was a significant decline in density of H. virescens eggs with increasing distance from the refuge. In contrast, there was no impact of refuge width on the density of H. zea eggs, nor was the slope of a regression of egg density and distance from the refuge significantly different from zero. We suggest that these differences reflect differences in the biology of the two insects

Survey of Subterranean Termite (Isoptera: Rhinotermitidae) Utilization of Temperate Forests

Both native and invasive subterranean termites (Isoptera: Rhinotermitidae), including the Formosan subterranean termite, are well known pests of urban areas, but little is known about their distribution or impact in forest ecosystems of the southeastern United States. Recently harvested timber stumps were mechanically inspected for the presence of subterranean termites in multiple locations across southern Mississippi and eastern Louisiana. A systematic line plot cruise with 100 x 200m spacing and1/20thha plots was implemented, and all stumps with a diameter greater than 7.6cm were inspected. In total, 7,413 stumps were inspected for the presence of subterranean termites, and 406 of those contained native subterranean termite (Reticulitermes spp) infestations. Light traps were also placed at 8 sites to detect the presence of subterranean termite alates. While no invasive Formosan subterranean termites were found during mechanical inspection of tree stumps, alates were captured in light traps at three sites. The proportion of stumps infested with subterranean termites was negatively correlated with the number of stumps in each plot. Although 6.27% of pine stumps and 1.86% of hardwood stumps were infested, no correlation was found between subterranean termite presence and type of stump (pine or hardwood). Infestations of stumps by subterranean termites ranged from 0.94% to 14.97% depending on site

Future Fitness of Female Insect Pests in Temporally Stable and Unstable Habitats and Its Impact on Habitat Utility as Refuges for Insect Resistance Management

The long-term fitness of individuals is examined in complex and temporally dynamic ecosystems. We call this multigeneration fitness measure “future fitness”. Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae) is a polyphagous insect that feeds on many wild and cultivated hosts. While four generations of H. zea occur during the cropping season in the U.S. Mid Southern agroecosysem, the latter two generations were of most interest, as corn (which has been largely nontransgenic in the Mid-South) dominates the first two generations in the cropping system. In simulations of the evolution of resistance to Bt-transgenic crops, cotton refuge areas were found to be significantly more effective than similar soybean acreages at delaying the evolution of resistance. Cotton is a suitable host for H. zea during two late summer generations, while a soybean field is suitable for only one of these generations, therefore soybean fields of other maturity groups were simulated as being attractive during the alternative generation. A hypothetical soybean variety was tested in which a single field would be attractive over both generations and it was found to be significantly more effective at delaying resistance than simulated conventional soybean varieties. Finally, the placement of individuals emerging at the start of the 3rd (first without corn) generation was simulated in either refuge cotton, conventional soybean and the hypothetical long attractive soybean and the mean number of offspring produced was measured at the end of the season. Although females in conventional and long soybean crops had the same expected fecundity, because of differences in temporal stability of the two crops, the long soybean simulations had significantly more H. zea individuals at the end of the season than the conventional soybean simulations. These simulations demonstrate that the long-term fecundity associated with an individual is dependent not only on the fecundity of that individual in its current habitat, but also the temporal stability of habitats, the ecosystem at large and the likelihood that the individual's offspring will move into different habitats

Giving ecological meaning to satellite-derived fire severity metrics across North American forests

Satellite-derived spectral indices such as the relativized burn ratio (RBR) allow fire severity maps to be produced in a relatively straightforward manner across multiple fires and broad spatial extents. These indices often have strong relationships with field-based measurements of fire severity, thereby justifying their widespread use in management and science. However, satellite-derived spectral indices have been criticized because their non-standardized units render them difficult to interpret relative to on-the-ground fire effects. In this study, we built a Random Forest model describing a field-based measure of fire severity, the composite burn index (CBI), as a function of multiple spectral indices, a variable representing spatial variability in climate, and latitude. CBI data primarily representing forested vegetation from 263 fires (8075 plots) across the United States and Canada were used to build the model. Overall, the model performed well, with a cross-validated R2 of 0.72, though there was spatial variability in model performance. The model we produced allows for the direct mapping of CBI, which is more interpretable compared to spectral indices. Moreover, because the model and all spectral explanatory variables were produced in Google Earth Engine, predicting and mapping of CBI can realistically be undertaken on hundreds to thousands of fires. We provide all necessary code to execute the model and produce maps of CBI in Earth Engine. This study and its products will be extremely useful to managers and scientists in North America who wish to map fire effects over large landscapes or regions

Impaired Growth and Force Production in Skeletal Muscles of Young Partially Pancreatectomized Rats: A Model of Adolescent Type 1 Diabetic Myopathy?

This present study investigated the temporal effects of type 1 diabetes mellitus (T1DM) on adolescent skeletal muscle growth, morphology and contractile properties using a 90% partial pancreatecomy (Px) model of the disease. Four week-old male Sprague-Dawley rats were randomly assigned to Px (n = 25) or Sham (n = 24) surgery groups and euthanized at 4 or 8 weeks following an in situ assessment of muscle force production. Compared to Shams, Px were hyperglycemic (>15 mM) and displayed attenuated body mass gains by days 2 and 4, respectively (both P<0.05). Absolute maximal force production of the gastrocnemius plantaris soleus complex (GPS) was 30% and 50% lower in Px vs. Shams at 4 and 8 weeks, respectively (P<0.01). GP mass was 35% lower in Px vs Shams at 4 weeks (1.24±0.06 g vs. 1.93±0.03 g, P<0.05) and 45% lower at 8 weeks (1.57±0.12 vs. 2.80±0.06, P<0.05). GP fiber area was 15–20% lower in Px vs. Shams at 4 weeks in all fiber types. At 8 weeks, GP type I and II fiber areas were ∼25% and 40% less, respectively, in Px vs. Shams (group by fiber type interactions, P<0.05). Phosphorylation states of 4E-BP1 and S6K1 following leucine gavage increased 2.0- and 3.5-fold, respectively, in Shams but not in Px. Px rats also had impaired rates of muscle protein synthesis in the basal state and in response to gavage. Taken together, these data indicate that exposure of growing skeletal muscle to uncontrolled T1DM significantly impairs muscle growth and function largely as a result of impaired protein synthesis in type II fibers

The North American tree-ring fire-scar network

Fire regimes in North American forests are diverse and modern fire records are often too short to capture important patterns, trends, feedbacks, and drivers of variability. Tree-ring fire scars provide valuable perspectives on fire regimes, including centuries-long records of fire year, season, frequency, severity, and size. Here, we introduce the newly compiled North American tree-ring fire-scar network (NAFSN), which contains 2562 sites, >37,000 fire-scarred trees, and covers large parts of North America. We investigate the NAFSN in terms of geography, sample depth, vegetation, topography, climate, and human land use. Fire scars are found in most ecoregions, from boreal forests in northern Alaska and Canada to subtropical forests in southern Florida and Mexico. The network includes 91 tree species, but is dominated by gymnosperms in the genus Pinus. Fire scars are found from sea level to >4000-m elevation and across a range of topographic settings that vary by ecoregion. Multiple regions are densely sampled (e.g., >1000 fire-scarred trees), enabling new spatial analyses such as reconstructions of area burned. To demonstrate the potential of the network, we compared the climate space of the NAFSN to those of modern fires and forests; the NAFSN spans a climate space largely representative of the forested areas in North America, with notable gaps in warmer tropical climates. Modern fires are burning in similar climate spaces as historical fires, but disproportionately in warmer regions compared to the historical record, possibly related to under-sampling of warm subtropical forests or supporting observations of changing fire regimes. The historical influence of Indigenous and non-Indigenous human land use on fire regimes varies in space and time. A 20th century fire deficit associated with human activities is evident in many regions, yet fire regimes characterized by frequent surface fires are still active in some areas (e.g., Mexico and the southeastern United States). These analyses provide a foundation and framework for future studies using the hundreds of thousands of annually- to sub-annually-resolved tree-ring records of fire spanning centuries, which will further advance our understanding of the interactions among fire, climate, topography, vegetation, and humans across North America