Resistance to insecticides is often linked with fitness costs. Although costs affecting lifetime reproduction in females will have the greatest effect on resistance evolution, fertilization costs in ...males, through less vigorous mating behavior or less effective sperm in resistant individuals, will slow the spread of resistance. We used a sterile male technique to measure the relative mating competitiveness of Colorado potato beetles, Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae), resistant or susceptible to imidacloprid. We showed that 5,000 Krad from a cesium-137 source was sufficient to sterilize male beetles. We tested mating competitiveness by placing a single resistant and a single susceptible male beetle with a virgin susceptible female in circular acetate enclosures surrounding potted potato plants, and we observed frequency of mating or mounting with each male and subsequent fertilization success. Resistant males mate just as often as susceptible males during 24-h competitive interactions. Hatch rate was correlated with the proportion of matings or mounts observed with the nonirradiated male, but no effect of the first or last male, nor of resistance on fertilization success was observed, and resistance does not seem to incur a behavioral or sperm-competitive fertilization cost.
Shadow competition, when sedentary foragers closer to a source of food reduce its availability to those further away, is predicted to increase with the size and density of a group. We tested the ...occurrence of shadow competition and examined its consequences for a burrowing spider Seothyra henscheli (Eresidae) in the Namib Desert. Differences between individual spiders occurring inside or on the periphery of clusters compared to solitary spiders were examined in a natural population, by experimental manipulation of densities and by computer simulation of the experimental manipulation. Spiders in the population grew more slowly in clusters than did solitary spiders and this was confirmed by the experiment. The experiment showed that spiders grew more rapidly on the periphery of a cluster than inside it, but that survival showed the opposite trend. The largest effect was in the highest density, where all spiders maintained active webs throughout the experiment, indicating a state of hunger. Modeling indicated that such effects may be explained by the way ants, the principal prey of the spiders, reach spider webs at different locations within the patches of different densities. Modeling confirmed that shadow competition adequately explains the patterns of foraging, growth and survival of sedentary foragers such as these spiders, and is likely to have wider implications for other sit-and-wait predators.
This paper uses Alistair Mant's colourful systems metaphor of the frog and the bicycle to explore the current changes in the NHS. Considering the implications of these system changes from this ...organisational health perspective, a possible leadership strategy is considered to navigate through the challenging transitional period.
•No statistically significant negative association was found between use of a tourniquet and number of ventilator days in the femoral or tibial fracture group.•Tourniquet use for other fractures did ...not increase the number of ventilator days for patients undergoing intramedullary nail insertion to treat femoral or tibial shaft fractures.•A potential protective effect of tourniquet use was shown in patients with upper extremity fractures and in those with both upper and lower extremity fractures.•The data presented in this study should reassure clinicians that tourniquet use for other fractures in either the upper or lower extremity at the same setting as reamed femoral or tibial nail insertion does not seem to increase risk for increased ventilator-dependent days.
Concern exists regarding the pulmonary effects of using tourniquets for secondary extremity fractures in patients also undergoing intramedullary nail (IMN) fixation of femoral or tibial shaft fractures. Our hypothesis was that tourniquet use would be associated with increased ventilator days.
At a Level I trauma center, we conducted a retrospective review of 1966 patients with 2018 fractures (1070 femoral shaft and 948 tibial shaft) treated with IMN from December 2006 to September 2014. Medical record review and bivariate and multiple variable regression analyses were conducted, and the main outcome measurement was number of ventilator days.
No statistically significant negative association was found between use of a tourniquet and number of ventilator days in the femoral or tibial fracture group. Use of tourniquets in the upper extremities showed a statistically significant decrease in amount of ventilator days in the femoral group (−2.2 days, p = 0.003) but no association in the tibial group (1.1 days, p = 0.36). Use of tourniquets concurrently in both upper and lower extremities of both femoral and tibial groups also had a protective effect (−6.8 days, p < 0.001 and −2.3 days, p = 0.009, respectively). Stratified and sensitivity analyses (to account for effects of mortality and missing data) showed consistently similar results.
Tourniquet use for secondary extremity fractures, in patients also undergoing IMN fixation for femoral or tibial shaft fractures, was not associated with an increased number of ventilator days. A potential protective effect of tourniquet use was shown in patients with upper extremity fractures and in those with both upper and lower extremity fractures.
Therapeutic Level III (Retrospective cohort study).
Colorado potato beetle, Leptinotarsa decemlineata (Say), is the most important insect defoliator of potatoes and is infamous for its ability to develop insecticide resistance. Sperm precedence is an ...important consideration in developing resistance management plans. We determined the precedence of sperm from a postdiapause spring mating by using irradiated sterile males. We also investigated whether spring mating (with or without fertilization) affects reproduction of overwintered females. Precedence of sperm from spring matings versus overwintered sperm from fall matings was almost complete. Some fertilization from fall matings did take place in this experiment, but it exceeded 10% in only one of the 22 pairings. Females mated only the previous fall laid fewer eggs than spring-mated females, but spring mating did not seem to improve the hatch rate of deposited eggs. On average, mated females started laying 1.6 d sooner than fall-mated females, but this difference was not significant. Hatch rate did not change with time. Precedence of spring matings over stored sperm can help compensate for assortative summer mating among resistant individuals due to differences in developmental time between refuges and treated areas.
Gas–solid chromatography was used to obtain values of the second gas–solid virial coefficient, B2s, in the temperature range from 392 to 511 K for 10 volatile, malodorous organic sulfur compounds; ...ethanethiol, 1-propanethiol, methyl sulfide, 2-propanethiol, 1-methyl-1-propanethiol, 2-methyl-1-propanethiol, 2-methyl-2-propanethiol, ethyl sulfide, ethyl methyl sulfide, and tert-butyl methyl sulfide. Carbopack C (Supelco Inc.), a graphitized carbon black powder, was used as the adsorbent. Beginning with a theoretical equation for the second gas–solid virial coefficient, it was shown how a quantitative structure–retention relation (QSRR) could be developed to correlate ln B2s and hence chromatographic retention times with calculated molar refractivity and connectivity index values for the thiols and thioethers. It was found that both the gas–solid interaction energies and the ln B2s values could be correlated with calculated adsorbate molar refractivity (r2=0.951) and (r2=0.961), respectively. Connectivity index and molar refractivity together provide a r2=0.989 correlation of the ten ln B2s values at 403 K. A set of 373 organic compounds with retention indices taken from the literature was used to further test our approach. The 373 molecules were divided into 10 structural subgroups and molar refractivities and connectivity indices were calculated and used to correlate their retention index values. An overall correlation of r2=0.982 for the retention indices of the 373 molecules was found.
Colorado potato beetle, Leptinotarsa decemlineata (Say), is a major pest of potatoes in North America, Europe, and parts of Asia. It adapts quickly to adverse environments, thereby limiting the ...longevity of control strategies. Better understanding of variability among geographically isolated populations of this insect might create an opportunity to customize control techniques for local conditions. We investigated insecticide resistance, heat tolerance, and growth potential in six beetle populations collected from different locations in the United States. Significant differences were detected in insecticide resistance, egg mass size, and egg hatchability among the tested populations. Large egg mass size appeared to be offset by lower egg hatchability. We also observed a female-biased sex ratio at least in one of the strains. Population growth rates were different among the strains, but this parameter was not correlated to insecticide resistance. This suggests that using allopatric populations in comparative studies of insecticide resistance might result in confusing effects of geographic isolation with the effects of selection toward resistance.
Cannibalism can have a large effect on population growth and survival in stressful environments, possibly including those created by insecticide use. In this study, we collected Colorado potato ...beetles from three isolated areas in the northeastern United States known for high levels of resistance to neonicotinoids. We measured resistance to imidacloprid in each of those populations, a laboratory susceptible population, and in hybrids between the three field populations and the laboratory susceptible population. We fed neonates eggs from resistant dams fed either imidaclopridtreated or untreated foliage to determine whether cannibals are exposed to toxins sequestered in eggs. We measured egg cannibalism by hatchlings within the clutch in each population and hybrids, and examined how fecundity and several variables associated with egg development varied among populations and with cannibalism, to see which traits might enhance or reduce cannibalism. Cannibalism varied significantly among populations, accounting for most of the variation in hatching success. Variability in egg development time and hatch rate in the absence of cannibalism in some populations affected rates of cannibalism. Resistance varied significantly among the field populations but was not related to cannibalism. Neonates fed eggs from dams on treated foliage showed signs of intoxication or death. Cannibalism appears to be part of a varying life history strategy in this species, with some populations laying larger and more cannibalistic clutches and the New York population laying smaller clutches with higher hatching success owing to reduced cannibalism.
Understanding the movement of invading organisms is critical to predicting invasion dynamics. The Colorado potato beetle, Leptinotarsa decemlineata (Say), is an invasive species on multiple spatial ...and temporal scales, and can serve as a model for studies of invasion dynamics. It is the major insect defoliator of potato in North America, and successful management requires an understanding of CPB invasions of individual fields. Its origin, spread, and biology, especially the cycle of annual invasions of agricultural potato fields, are described. Approaches to reducing the size of colonizing populations include rotation, delay of planting, and treatments of field margins. Rotation and sub-lethal insecticide treatments can slow the establishment of invasions within fields. These approaches interact with a late season diapause switch away from reproduction to reduce the impact of CPB. The refuge approach to delaying the fixation of resistance alleles is designed to encourage alleles for susceptibility to invade treated areas. We present data from an experimental refuge crop planted adjacent to a field treated with imidacloprid, an insecticide for which there is high variation in resistance. The treated field was four times as resistant as the untreated side, and a cline in resistance was formed from the untreated to the treated portion of the field. The cline width of about 100m provides an empirical basis for designing refuges to enhance the spread of alleles for susceptibility into treated areas and prevent fixation of resistance in the summer generation.PUBLICATION ABSTRACT
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