A method for sampling parasitized Drosophila suzukii (Diptera: Drosophilidae) puparia from soil

Methods to measure the diversity and biological control impact of parasitoids for the control of spotted-wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) are being developed in support of biological control programs around the world. Existing methods to determine parasitism levels and parasitoid species composition focus on sampling D. suzukii within fresh and rotting fruit. However, many D. suzukii pupate in the soil or in dropped fruit, where additional parasitism could occur and where their parasitoids are thought to overwinter. Here we introduce a method for extracting parasitized D. suzukii puparia from the soil through a sieve and flotation system, allowing for effective collection of puparia, from which parasitoids can then be reared. Although the method considerably underestimates the absolute number of puparia in soil samples, it nonetheless yields a high number of puparia relative to sampling effort and provides a robust estimate of the relative abundance of puparia among samples. Using this method, we confirmed that at least 5 species of parasitoids, including some that have rarely been detected in past studies, overwinter in their immature stages inside D. suzukii puparia in south coastal British Columbia, Canada. The ability to sample puparia from the soil will lead to a more comprehensive view of both D. suzukii and parasitoid abundance throughout the season, help confirm parasitoid establishment following intentional releases, and provide a way to measure the diversity of parasitoid species and potential interactions among parasitoids (e.g., hyper- or klepto-parasitism) that may often occur on the soil surface.

Adventive Larval Parasitoids Reconstruct Their Close Association with Spotted-Wing Drosophila in the Invaded North American Range

Two species of larval parasitoids of the globally invasive fruit pest, Drosophila suzukii (Diptera: Drosophilidae), Leptopilina japonica, and Ganaspis brasiliensis (both Hymenoptera: Figitidae), were detected in British Columbia, Canada in 2016 and 2019, respectively. Both are presumed to have been unintentionally introduced from Asia; however, the extent of their establishment across different habitats with diverse host plants used by D. suzukii was unclear. In addition, there was no knowledge of the temporal dynamics of parasitism of D. suzukii by these two parasitoids. To address these gaps, we repeatedly sampled the fruits of known host plants of D. suzukii over the entire 2020 growing season in British Columbia. We documented the presence of L. japonica and G. brasiliensis and estimated the apparent percentage of D. suzukii parasitized among host plant species. Across a large region of southwestern British Columbia, both L. japonica and G. brasiliensis were found to be very common across a variety of mostly unmanaged habitats over the entire course of the season (May-October) in the fruits of most host plants known to host D. suzukii larvae. Parasitism of D. suzukii was variable (0-66% percent parasitism) and appeared to be time-structured. Our study demonstrates that the close association between the two larval parasitoids and D. suzukii that exists in Asia has evidently been reconstructed in North America, resulting in the highest parasitism levels of D. suzukii yet recorded outside of its area of origin.

A Coordinated Sampling and Identification Methodology for Larval Parasitoids of Spotted-Wing Drosophila

We provide recommendations for sampling and identification of introduced larval parasitoids of spotted-wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae). These parasitoids are either under consideration for importation (aka classical) biological control introductions, or their adventive (presumed to have been accidentally introduced) populations have recently been discovered in North America and Europe. Within the context of the ecology of D. suzukii and its parasitoids, we discuss advantages and disadvantages of estimating larval parasitism levels using different methods, including naturally collected fruit samples and sentinel baits. For most situations, we recommend repeated sampling of naturally occurring fruit rather than using sentinel baits to monitor seasonal dynamics of host plant-Drosophila-parasitoid associations. We describe how to separate Drosophilidae puparia from host fruit material in order to accurately estimate parasitism levels and establish host-parasitoid associations. We provide instructions for identification of emerging parasitoids and include a key to the common families of parasitoids of D. suzukii. We anticipate that the guidelines for methodology and interpretation of results that we provide here will form the basis for a large, multi-research team sampling effort in the coming years to characterize the biological control and nontarget impacts of accidentally and intentionally introduced larval parasitoids of D. suzukii in several regions of the world.

Genetic similarity of island populations of tent caterpillars during successive outbreaks

Cyclic or fluctuating populations experience regular periods of low population density. Genetic bottlenecks during these periods could give rise to temporal or spatial genetic differentiation of populations. High levels of movement among increasing populations, however, could ameliorate any differences and could also synchronize the dynamics of geographically separated populations. We use microsatellite markers to investigate the genetic differentiation of four island and one mainland population of western tent caterpillars, Malacosoma californicum pluviale, in two periods of peak or pre-peak density separated by 8 years. Populations showed high levels of genetic variation and little genetic differentiation either temporally between peaks or spatially among sites. Mitochondrial haplotypes were also shared between one island population and one mainland population in the two years studied. An isolation-by-distance analysis showed the FST values of the two geographically closest populations to have the highest level of differentiation in both years. We conclude that high levels of dispersal among populations maintain both synchrony of population dynamics and override potential genetic differentiation that might occur during population troughs. As far we are aware, this is the first time that genetic similarity between temporally separated population outbreaks in insects has been investigated. A review of genetic data for both vertebrate and invertebrate species of cyclic animals shows that a lack of spatial genetic differentiation is typical, and may result from high levels of dispersal associated with fluctuating dynamics.

The availability of research data declines rapidly with article age

Policies ensuring that research data are available on public archives are increasingly being implemented at the government [1], funding agency [2-4], and journal [5, 6] level. These policies are predicated on the idea that authors are poor stewards of their data, particularly over the long term [7], and indeed many studies have found that authors are often unable or unwilling to share their data [8-11]. However, there are no systematic estimates of how the availability of research data changes with time since publication. We therefore requested data sets from a relatively homogenous set of 516 articles published between 2 and 22 years ago, and found that availability of the data was strongly affected by article age. For papers where the authors gave the status of their data, the odds of a data set being extant fell by 17% per year. In addition, the odds that we could find a working e-mail address for the first, last, or corresponding author fell by 7% per year. Our results reinforce the notion that, in the long term, research data cannot be reliably preserved by individual researchers, and further demonstrate the urgent need for policies mandating data sharing via public archives.

Mandated data archiving greatly improves access to research data

The data underlying scientific papers should be accessible to researchers both now and in the future, but how best can we ensure that these data are available? Here we examine the effectiveness of four approaches to data archiving: no stated archiving policy, recommending (but not requiring) archiving, and two versions of mandating data deposition at acceptance. We control for differences between data types by trying to obtain data from papers that use a single, widespread population genetic analysis, structure. At one extreme, we found that mandated data archiving policies that require the inclusion of a data availability statement in the manuscript improve the odds of finding the data online almost 1000-fold compared to having no policy. However, archiving rates at journals with less stringent policies were only very slightly higher than those with no policy at all. We also assessed the effectiveness of asking for data directly from authors and obtained over half of the requested datasets, albeit with ∼8 d delay and some disagreement with authors. Given the long-term benefits of data accessibility to the academic community, we believe that journal-based mandatory data archiving policies and mandatory data availability statements should be more widely adopted.

Evolution and the microbial control of insects

Insect pathogens can be utilized in a variety of pest management approaches, from inundative release to augmentation and classical biological control, and microevolution and the consideration of evolutionary principles can potentially influence the success of all these strategies. Considerable diversity exists in natural entomopathogen populations and this diversity can be either beneficial or detrimental for pest suppression, depending on the pathogen and its mode of competition, and this should be considered in the selection of isolates for biological control. Target hosts can exhibit considerable variation in their susceptibility to entomopathogens, and cases of field-evolved resistance have been documented for Bacillus thuringiensis and baculoviruses. Strong selection, limited pathogen diversity, reduced gene flow, and host plant chemistry are linked to cases of resistance and should be considered when developing resistance management strategies. Pre- and post-release monitoring of microbial control programs have received little attention; however, to date there have been no reports of host-range evolution or long-term negative effects on nontarget hosts. Comparative analyses of pathogen population structure, virulence, and host resistance over time are required to elucidate the evolutionary dynamics of microbial control systems.

Multiple mating and family structure of the western tent caterpillar, Malacosoma californicum pluviale: impact on disease resistance

BACKGROUND

Levels of genetic diversity can strongly influence the dynamics and evolutionary changes of natural populations. Survival and disease resistance have been linked to levels of genetic diversity in eusocial insects, yet these relationships remain untested in gregarious insects where disease transmission can be high and selection for resistance is likely to be strong.

METHODOLOGY/PRINCIPAL FINDINGS

Here we use 8 microsatellite loci to examine genetic variation in 12 families of western tent caterpillars, Malacosoma californicum pluviale from four different island populations to determine the relationship of genetic variability to survival and disease resistance. In addition these genetic markers were used to elucidate the population structure of western tent caterpillars. Multiple paternity was revealed by microsatellite markers, with the number of sires estimated to range from one to three per family (mean ± SE  = 1.92±0.23). Observed heterozygosity (H(O)) of families was not associated to the resistance of families to a nucleopolyhedrovirus (NPV) (r = 0.161, F(1,12)  = 0.271, P = 0.614), a major cause of mortality in high-density populations, but was positively associated with larval survival (r = 0.635, F(1,10)  = 5.412, P = 0.048). Genetic differentiation among the families was high (F(ST) = 0.269, P<0.0001), and families from the same island were as differentiated as were families from other islands.

CONCLUSION/SIGNIFICANCE

We have been able to describe and characterize 8 microsatellite loci, which demonstrate patterns of variation within and between families of western tent caterpillars. We have discovered an association between larval survival and family-level heterozygosity that may be relevant to the population dynamics of this cyclic forest lepidopteran, and this will be the topic of future work.

Genetic analysis of cabbage loopers, Trichoplusia ni (Lepidoptera: Noctuidae), a seasonal migrant in western North America

Long-range migrations of many wind-borne noctuid moths will have been influenced by the expansion of agriculture that provides greater availability of food plants along the migratory route. The migratory, agricultural pest, Trichoplusia ni (cabbage looper) over-winters in southern California and each summer migrates as far north as British Columbia. We explored the degree of genetic connectivity of populations over this migratory range. Preliminary investigation of seven mitochondrial gene regions found little to no variation among 13 populations, while partial regions of the NADH dehydrogenase subunits 1 and 4 in 42 individuals revealed eight and six haplotypes, respectively. The pattern of haplotype distribution indicated genetic homogeneity of persistent populations in California but weak differentiation among populations further north. Four highly variable amplified fragment length polymorphism primer combinations generated 167 polymorphic bands, with heterozygosity levels ranging from 0.250 to 0.302. Pairwise F_ST values and clustering analyses also showed similarty among populations in California with some differentiation among populations initiated from the annual migration. Overall, some differentiation occurs among temporary, annual migratory populations but no pattern occurs with distance from the source population. Population subdivision in British Columbia associated with greenhouses has the greatest impact on genetic differentiation.

Lethal and sub-lethal effects of spinosad on bumble bees (Bombus impatiens Cresson)

Recent developments of new families of pesticides and growing awareness of the importance of wild pollinators for crop pollination have stimulated interest in potential effects of novel pesticides on wild bees. Yet pesticide toxicity studies on wild bees remain rare, and few studies have included long-term monitoring of bumble bee colonies or testing of foraging ability after pesticide exposure. Larval bees feeding on exogenous pollen and exposed to pesticides during development may result in lethal or sub-lethal effects during the adult stage. We tested the effects of a naturally derived biopesticide, spinosad, on bumble bee (Bombus impatiens Cresson) colony health, including adult mortality, brood development, weights of emerging bees and foraging efficiency of adults that underwent larval development during exposure to spinosad. We monitored colonies from an early stage, over a 10-week period, and fed spinosad to colonies in pollen at four levels: control, 0.2, 0.8 and 8.0 mg kg(-1), during weeks 2 through 5 of the experiment. At concentrations that bees would likely encounter in pollen in the wild (0.2-0.8 mg kg(-1)) we detected minimal negative effects to bumble bee colonies. Brood and adult mortality was high at 8.0 mg kg(-1) spinosad, about twice the level that bees would be exposed to in a 'worst case' field scenario, resulting in colony death two to four weeks after initial pesticide exposure. At more realistic concentrations there were potentially important sub-lethal effects. Adult worker bees exposed to spinosad during larval development at 0.8 mg kg(-1) were slower foragers on artificial complex flower arrays than bees from low or no spinosad treated colonies. Inclusion of similar sub-lethal assays to detect effects of pesticides on pollinators would aid in development of environmentally responsible pest management strategies.

Effects of clothianidin on Bombus impatiens (Hymenoptera: Apidae) colony health and foraging ability

We conducted laboratory experiments to investigate the lethal and sublethal effects of clothianidin on bumble bee, Bombus impatiens Cresson, colony health and foraging ability. Bumble bee colonies were exposed to 6 ppb clothianidin, representing the highest residue levels found in field studies on pollen, and a higher dose of 36 ppb clothianidin in pollen. Clothianidin did not effect pollen consumption, newly emerged worker weights, amount of brood or the number of workers, males, and queens at either dose. The foraging ability of worker bees tested on an artificial array of complex flowers also did not differ among treatments. These results suggest that clothianidin residues found in seed-treated canola and possibly other crops will not adversely affect the health of bumble bee colonies or the foraging ability of workers.

Effects of clothianidin on Bombus impatiens (Hymenoptera: Apidae) colony health and foraging ability

We conducted laboratory experiments to investigate the lethal and sublethal effects of clothianidin on bumble bee, Bombus impatiens Cresson, colony health and foraging ability. Bumble bee colonies were exposed to 6 ppb clothianidin, representing the highest residue levels found in field studies on pollen, and a higher dose of 36 ppb clothianidin in pollen. Clothianidin did not effect pollen consumption, newly emerged worker weights, amount of brood or the number of workers, males, and queens at either dose. The foraging ability of worker bees tested on an artificial array of complex flowers also did not differ among treatments. These results suggest that clothianidin residues found in seed-treated canola and possibly other crops will not adversely affect the health of bumble bee colonies or the foraging ability of workers.

Stretch-dependent activation and desensitization of mitogen-activated protein kinase in carotid arteries

Arterial smooth muscle stretch is an important physiological modulator of vascular function. To identify intracellular processes altered during muscle stretch, we found previously that extracellular signal-regulated kinase-mitogen-activated protein kinase (MAPK) activity increased in response to the application of mechanical loads. In the present study, stretch-dependent activation of MAPK in porcine carotid arteries was investigated as was the phosphorylation of the thin filament-binding protein caldesmon, which is known to be a substrate for the kinase in fully differentiated smooth muscle. MAPK activity was 67 pmol.min-1.mg protein-1 in unloaded muscle strips immediately after attachment to force transducers and 139 pmol.min-1.mg protein-1 within 30 s of muscle stretch. When muscle strips were continually stretched, MAPK activity remained elevated for approximately 2 h and then decreased over 16 h to 16 pmol.min-1.mg protein-1. When muscle strips were stretched and then unloaded, MAPK activity decreased within 1 h to the level present in the muscle before the stretch. These effects of muscle stretch on MAPK activity were additive to the effects of KCl or phorbol ester stimulation and were partially inhibited by reducing extracellular Ca2+. Eliminating extracellular Ca2+ had no effect on phorbol 12,13-dibutyrate (PDBu)-dependent contractions or MAPK activity; however, KCl-dependent contractions and MAPK activity were completely abolished by this procedure. An antibody specific for detecting caldesmon phosphorylated by MAPK, vs. protein kinase C (PKC), was developed and used to assess relative caldesmon phosphorylation in unstimulated and PDBu-stimulated muscle strips. In all cases investigated, the level of MAPK activity correlated with phosphocaldesmon immunoreactivity. Because arterial MAPK activity is regulated by PKC- and stretch-dependent mechanisms, these data are consistent with a role for MAPK and the subsequent phosphorylation of caldesmon as mediators in the stretch activation of vascular smooth muscle.

Cyclin D1 overexpression promotes cardiomyocyte DNA synthesis and multinucleation in transgenic mice

D-type cyclin/cyclin-dependent kinase (CDK) complexes regulate transit through the restriction point of the cell cycle, and thus are required for the initiation of DNA synthesis. Transgenic mice which overexpress cyclin D1 in the heart were produced to determine if D-type cyclin deregulation would alter myocardial development. Cyclin D1 overexpression resulted in a concomitant increase in CDK4 levels in the adult myocardium, as well as modest increases in proliferating cell nuclear antigen and CDK2 levels. Flow cytometric and morphologic analyses of dispersed cell preparations indicated that the adult transgenic cardiomyocytes had abnormal patterns of multinucleation. Histochemical analyses confirmed a marked increase in number of cardiomyocyte nuclei in sections prepared from the transgenic mice as compared with those from control animals. Tritiated thymidine incorporation analyses revealed sustained cardiomyocyte DNA synthesis in adult transgenic hearts.

Intracellular signaling by 8-epi-prostaglandin F2 alpha is mediated by thromboxane A2/prostaglandin endoperoxide receptors in porcine carotid arteries

To investigate the mechanisms for intracellular signaling and increased vascular tone by 8-epi-prostaglandin F2 alpha (8-epi-PGF2 alpha), we measured mitogen-activated protein kinase (MAPK) activity and myosin regulatory light chain (LC20) phosphorylation in porcine carotid arteries incubated with 8-epi-PGF2 alpha or PGF2 alpha. With stimulation by either 8-epi-PGF2 alpha or PGF2 alpha. MAPK activity and the force of contraction rose in parallel and were maintained during the time of exposure to agonist (2 hours). LC20 phosphorylation levels rose and then partially declined during stimulation with either agonist. The effects of 8-epi-PGF2 alpha on contraction, MAPK activity, and myosin light chain phosphorylation were completely inhibited by the receptor antagonists, SQ-29548 and BMS-180291; the effects of PGF2 alpha were only partially inhibited by these compounds. Thus, intracellular signaling by 8-epi-PGF2 alpha in fully differentiated vascular smooth muscle, resulting in MAPK activation and increased myosin phosphorylation, is specifically mediated by an activation of thromboxane A2/prostaglandin endoperoxide receptors. Lipid peroxidation and 8-epi-PGF2 alpha production, resulting from such vascular pathological processes as atherosclerosis, lead to an activation of two intracellular signaling pathways in smooth muscle: one pathway results in the activation of MAPK, while the other results in myosin light chain phosphorylation.

Activation of mitogen-activated protein kinase in porcine carotid arteries

The thin-filament protein h-caldesmon (the high molecular weight isoform of caldesmon) is phosphorylated in resting and contracted porcine carotid arteries. Phosphorylation of h-caldesmon in intact tissue occurs at sites that are covalently modified by mitogen-activated protein kinase (MAPK) in vitro. In this study, we have evaluated MAPK activation in arteries in response to mechanical load and pharmacological stimulation. MAPK was extracted from resting and stimulated porcine carotid arteries and then partially purified by anion-exchange fast-performance liquid chromatography. MAPK activity was separated into two peaks corresponding to the tyrosine-phosphorylated 42- and 44-kD isoforms of MAPK (p42MAPK and p44MAPK, respectively). Of the total MAPK activity, 42% was associated with p42MAPK, and 58% was associated with p44MAPK, this percentage was not altered by stimulation of the muscles with either KCl (110 mmol/L) or phorbol 12,13-dibutyrate (PDBu, 1 mumol/L). Both p42MAPK and p44MAPK, purified from porcine carotid arteries, phosphorylated h-caldesmon at the same sites and to levels approaching or > 1 mol phosphate per mole protein. In unloaded muscle strips, MAPK activity was 39 pmol.min-1.mg protein-1 when assayed with the peptide substrate APRTPG-GRR. MAPK activity increased in response to incremental mechanical loading to a maximum of 99 pmol.min-1.mg protein-1 at 16 x 10(3) N/m2. MAPK activity could be further increased in loaded muscles by pharmacological stimulation. With KCl stimulation, MAPK activities rose to a peak of 205 pmol.min-1.mg protein-1 at 10 minutes and then declined to basal values at 30 and 60 minutes.(ABSTRACT TRUNCATED AT 250 WORDS)