Temporal population genetic structure of Phormia regina (Diptera: Calliphoridae)

The genetic structure of forensically important blow fly (Brauer & Bergenstamm) (Diptera: Calliphoridae) populations has remained elusive despite high relatedness within wild-caught samples. This research aimed to determine if the implementation of a high-resolution spatiotemporal sampling design would reveal latent genetic structure among blow fly populations and to elucidate any environmental impacts on observed patterns of genetic structure. Adult females of the black blow fly, Phormia regina (Meigen) (Diptera: Calliphoridae), were collected from 9 urban parks in Indiana, USA over 3 yr and genotyped at 6 polymorphic microsatellite loci. The data analysis involved 3 clustering methods: principal coordinate analysis (PCoA), discriminant analysis of principal components (DAPC), and STRUCTURE. While the PCoA did not uncover any discernible clustering patterns, the DAPC and STRUCTURE analyses yielded significant results, with 9 and 4 genetic clusters, respectively. Visualization of the STRUCTURE bar plot revealed N = 11 temporal demarcations indicating barriers to gene flow. An analysis of molecular variance of these STRUCTURE-inferred populations supported strong temporally driven genetic differentiation (FST = 0.048, F'ST = 0.664) relative to geographic differentiation (FST = 0.009, F'ST = 0.241). Integrated Nested Laplace Approximation and Boosted Regression Tree analyses revealed that collection timepoint and 4 main abiotic factors (temperature, humidity, precipitation, and wind speed) were associated with the genetic subdivisions observed for P. regina. A complex interplay between environmental conditions, the unique reproductive strategies of the blow fly, and the extensive dispersal abilities of these organisms likely drives the strong genetic structure of P. regina in the Midwestern US.

Insects as Chemical Sensors: Detection of Chemical Warfare Agent Simulants and Hydrolysis Products in the Blow Fly Using LC-MS/MS

In this work, blow flies were investigated as environmental chemical sample collectors following a chemical warfare attack (CWA). Blow flies sample the environment as they search for water and food sources and can be trapped from kilometers away using baited traps. Three species of blow flies were exposed to CWA simulants to determine the persistence and detectability of these compounds under varying environmental conditions. A liquid chromatography mass spectrometry (LC-MS/MS) method was developed to detect CWA simulants and hydrolysis products from fly guts. Flies were exposed to the CWA simulants dimethyl methylphosphonate and diethyl phosphoramidate as well as the pesticide dichlorvos, followed by treatment-dependent temperature and humidity conditions. Flies were sacrificed at intervals within a 14 day postexposure period. Fly guts were extracted and analyzed with the LC-MS/MS method. The amount of CWA simulant in fly guts decreased with time following exposure but were detectable 14 days following exposure, giving a long window of detectability. In addition to the analysis of CWA simulants, isopropyl methylphosphonic acid, the hydrolysis product of sarin, was also detected in blow flies 14 days post exposure. This work demonstrates the potential to obtain valuable samples from remote or access-restricted areas without risking lives.

Global population genetic structure and demographic trajectories of the black soldier fly, Hermetia illucens

Background

The black soldier fly (Hermetia illucens) is the most promising insect candidate for nutrient-recycling through bioconversion of organic waste into biomass, thereby improving sustainability of protein supplies for animal feed and facilitating transition to a circular economy. Contrary to conventional livestock, genetic resources of farmed insects remain poorly characterised. We present the first comprehensive population genetic characterisation of H. illucens. Based on 15 novel microsatellite markers, we genotyped and analysed 2862 individuals from 150 wild and captive populations originating from 57 countries on seven subcontinents.

Results

We identified 16 well-distinguished genetic clusters indicating substantial global population structure. The data revealed genetic hotspots in central South America and successive northwards range expansions within the indigenous ranges of the Americas. Colonisations and naturalisations of largely unique genetic profiles occurred on all non-native continents, either preceded by demographically independent founder events from various single sources or involving admixture scenarios. A decisive primarily admixed Polynesian bridgehead population serially colonised the entire Australasian region and its secondarily admixed descendants successively mediated invasions into Africa and Europe. Conversely, captive populations from several continents traced back to a single North American origin and exhibit considerably reduced genetic diversity, although some farmed strains carry distinct genetic signatures. We highlight genetic footprints characteristic of progressing domestication due to increasing socio-economic importance of H. illucens, and ongoing introgression between domesticated strains globally traded for large-scale farming and wild populations in some regions.

Conclusions

We document the dynamic population genetic history of a cosmopolitan dipteran of South American origin shaped by striking geographic patterns. These reflect both ancient dispersal routes, and stochastic and heterogeneous anthropogenic introductions during the last century leading to pronounced diversification of worldwide structure of H. illucens. Upon the recent advent of its agronomic commercialisation, however, current human-mediated translocations of the black soldier fly largely involve genetically highly uniform domesticated strains, which meanwhile threaten the genetic integrity of differentiated unique local resources through introgression. Our in-depth reconstruction of the contemporary and historical demographic trajectories of H. illucens emphasises benchmarking potential for applied future research on this emerging model of the prospering insect-livestock sector.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12915-021-01029-w.

Blow fly stable isotopes reveal larval diet: A case study in community level anthropogenic effects

Response to human impacts on the environment are typically initiated too late to remediate negative consequences. We present the novel use of stable isotope analysis (SIA) of blow flies to determine human influences on vertebrate communities in a range of human-inhabited environments, from a pristine national park to a dense metropolitan area. The refrain "you are what you eat" applies to the dietary isotope record of all living organisms, and for carrion-breeding blow flies, this translates to the type of carcasses present in an environment. Specifically, we show that carnivore carcasses make up a large proportion of the adult fly's prior larval diet, which contrasts to what has been reportedly previously for the wild adult fly diet (which consists of mostly herbivore resources). Additionally, we reveal the potential impact of human food on carcasses that were fed on by blow flies, underscoring the human influences on wild animal populations. Our results demonstrate that using SIA in conjunction with other methods (e.g., DNA analysis of flies) can reveal a comprehensive snapshot of the vertebrate community in a terrestrial ecosystem.

The oncometabolite L-2-hydroxyglutarate is a common product of dipteran larval development

The oncometabolite L-2-hydroxyglutarate (L-2HG) is considered an abnormal product of central carbon metabolism that is capable of disrupting chromatin architecture, mitochondrial metabolism, and cellular differentiation. Under most circumstances, mammalian tissues readily dispose of this compound, as aberrant L-2HG accumulation induces neurometabolic disorders and promotes renal cell carcinomas. Intriguingly, Drosophila melanogaster larvae were recently found to accumulate high L-2HG levels under normal growth conditions, raising the possibility that L-2HG plays a unique role in insect metabolism. Here we explore this hypothesis by analyzing L-2HG levels in 18 insect species. While L-2HG was present at low-to-moderate levels in most of these species (<100 pmol/mg; comparable to mouse liver), dipteran larvae exhibited a tendency to accumulate high L-2HG concentrations (>100 pmol/mg), with the mosquito Aedes aegypti, the blow fly Phormia regina, and three representative Drosophila species harboring concentrations that exceed 1 nmol/mg - levels comparable to those measured in mutant mice that are unable to degrade L-2HG. Overall, our findings suggest that one of the largest groups of animals on earth commonly generate high concentrations of an oncometabolite during juvenile growth, hint at a role for L-2HG in the evolution of dipteran development, and raise the possibility that L-2HG metabolism could be targeted to restrict the growth of key disease vectors and agricultural pests.

The genomes of a monogenic fly: views of primitive sex chromosomes

The production of male and female offspring is often determined by the presence of specific sex chromosomes which control sex-specific expression, and sex chromosomes evolve through reduced recombination and specialized gene content. Here we present the genomes of Chrysomya rufifacies, a monogenic blow fly (females produce female or male offspring, exclusively) by separately sequencing and assembling each type of female and the male. The genomes (> 25X coverage) do not appear to have any sex-linked Muller F elements (typical for many Diptera) and exhibit little differentiation between groups supporting the morphological assessments of C. rufifacies homomorphic chromosomes. Males in this species are associated with a unimodal coverage distribution while females exhibit bimodal coverage distributions, suggesting a potential difference in genomic architecture. The presence of the individual-sex draft genomes herein provides new clues regarding the origination and evolution of the diverse sex-determining mechanisms observed within Diptera. Additional genomic analysis of sex chromosomes and sex-determining genes of other blow flies will allow a refined evolutionary understanding of how flies with a typical X/Y heterogametic amphogeny (male and female offspring in similar ratios) sex determination systems evolved into one with a dominant factor that results in single sex progeny in a chromosomally monomorphic system.

Genetic and phenotypic consequences of early domestication in black soldier flies (Hermetia illucens)

The black soldier fly, Hermetia illucens, is an emerging biotechnological agent with its larvae being effective converters of organic waste into usable bio-products including protein and lipids. To date, most operations use unimproved commercial populations produced by mass rearing, without cognisance of specific breeding strategies. The genetic and phenotypic consequences of these commercial practices remain unknown and could have a significant impact on long-term population viability and productivity. The aim of this study was thus to assess the genetic and phenotypic changes during the early phases of colony establishment and domestication in the black soldier fly. An experimental colony was established from wild founder flies and a new microsatellite marker panel was developed to assess population genetic parameters along with the phenotypic characteristics of each generational cohort under captive breeding. The experimental colony was characterised by a small effective population size, subsequent loss of genetic diversity and rapid genetic and phenotypic differentiation between the generational cohorts. Ultimately, the population collapsed by the fifth generation, most likely owing to the adverse effect of inbreeding depression following the fixation of deleterious alleles. Species with r-selected life history characteristics (e.g. short life-span, high fecundity and low larval survival) are known to pose particular challenges for genetic management. The current study suggests that sufficient genetic and phenotypic variations exist in the wild population and that domestication and strain development could be achieved with careful population augmentation and selection during the early stages of colony establishment.

Improved transgenic sexing strains for genetic control of the Australian sheep blow fly Lucilia cuprina using embryo-specific gene promoters

For genetic approaches for controlling insect pests such as the sterile insect technique (SIT), it is advantageous to release only males as females are ineffective as control agents and they consume about 50% of the diet. Here we developed tetracycline-repressible Lucilia cuprina transgenic strains in which adult females were fully fertile and viable on a diet that lacked tetracycline and all of their female offspring died at the embryo stage. The transgenic strains are an improvement over the strains we developed previously, which had the disadvantage that adult females on diet without tetracycline were sterile and died prematurely. This was possibly due to the low level expression of the effector gene in ovaries. In the strains developed in this study, the early promoters from L. cuprina nullo or Cochliomyia macellaria CG14427 genes were used to drive the tetracycline transactivator (tTA) expression in the early embryo. In the absence of tetracycline, tTA activates expression of the proapoptotic gene Lshid which contains a female-specific intron. Consequently, only females produce active HID protein and die at the embryo stage. Crossing the tTA-expressing driver lines with an RFPex reporter line confirmed that there was no expression of the effector gene in the ovary. These new embryonic L. cuprina transgenic sexing strains hold great promise for genetic control programs and the system reported here might also be transferable to other major calliphorid livestock pests such as the New World screwworm, Cochliomyia hominivorax.

Female Blow Flies As Vertebrate Resource Indicators

Rapid vertebrate diversity evaluation is invaluable for monitoring changing ecosystems worldwide. Wild blow flies naturally recover DNA and chemical signatures from animal carcasses and feces. We demonstrate the power of blow flies as biodiversity monitors through sampling of flies in three environments with varying human influences: Indianapolis, IN and two national parks (the Great Smoky Mountains and Yellowstone). Dissected fly guts underwent vertebrate DNA sequencing (12S and 16S rRNA genes) and fecal metabolite screening. Integrated Nested Laplace Approximation (INLA) was used to determine the most important abiotic factor influencing fly-derived vertebrate richness. In 720 min total sampling time, 28 vertebrate species were identified, with 42% of flies containing vertebrate resources: 23% DNA, 5% feces, and 14% contained both. The species of blow fly used was not important for vertebrate DNA recovery, however the use of female flies versus male flies directly influenced DNA detection. Temperature was statistically relevant across environments in maximizing vertebrate detection (mean = 0.098, sd = 0.048). This method will empower ecologists to test vertebrate community ecology theories previously out of reach due practical challenges associated with traditional sampling.

Ubiquity of polystyrene digestion and biodegradation within yellow mealworms, larvae of Tenebrio molitor Linnaeus (Coleoptera: Tenebrionidae)

Academics researchers and "citizen scientists" from 22 countries confirmed that yellow mealworms, the larvae of Tenebrio molitor Linnaeus, can survive by eating polystyrene (PS) foam. More detailed assessments of this capability for mealworms were carried out by12 sources: five from the USA, six from China, and one from Northern Ireland. All of these mealworms digested PS foam. PS mass decreased and depolymerization was observed, with appearance of lower molecular weight residuals and functional groups indicative of oxidative transformations in extracts from the frass (insect excrement). An addition of gentamycin (30 mg g^-1), a bactericidal antibiotic, inhibited depolymerization, implicating the gut microbiome in the biodegradation process. Microbial community analyses demonstrated significant taxonomic shifts for mealworms fed diets of PS plus bran and PS alone. The results indicate that mealworms from diverse locations eat and metabolize PS and support the hypothesis that this capacity is independent of the geographic origin of the mealworms, and is likely ubiquitous to members of this species.

New Distribution Record for Lucilia cuprina (Diptera: Calliphoridae) in Indiana, United States

Determining range expansion for insect species is vital in order to evaluate their impact on new ecosystems and communities. This is particularly important for species which could be potentially harmful to humans or domestic animals. Lucilia cuprina Wiedemann (Diptera: Calliphoridae) can act as a facultative ectoparasite and has an extensive history as the primary inducer of sheep-strike in Australia, New Zealand, and Africa. We present here the first record of this species in Indiana, United States. Lucilia cuprina's range expansion northward in the United States may be indicative of changing environmental conditions conducive to the proliferation of this species into historically cooler climates. The presence of this species could significantly impact forensic death investigations utilizing dipteran larvae to estimate a minimum postmortem interval. If range expansion of this species is not taken into account by a forensic entomologist (especially if L. cuprina is not known previously in their region), an inaccurate minimum postmortem interval (PMIMIN) estimation may be made, given the differences in development times for both species. Therefore, the range expansion of this fly could have large impacts for many different entomological disciplines.

Amplified fragment length polymorphism analysis supports the valid separate species status of Lucilia caesar and L. illustris (Diptera: Calliphoridae)

Common DNA-based species determination methods fail to distinguish some blow flies in the forensically and medically important genus Lucilia Robineau-Desvoidy. This is a practical problem, and it has also been interpreted as casting doubt on the validity of some morphologically defined species. An example is Lucilia illustris and L. caesar, which co-occur in Europe whilst only L. illustris has been collected in North America. Reports that these species shared both mitochondrial and nuclear gene sequences, along with claims that diagnostic morphological characters are difficult to interpret, were used to question their separate species status. We report here that amplified fragment length polymorphism profiles strongly support the validity of both species based on both assignment and phylogenetic analysis, and that traditional identification criteria based on male and female genital morphology are more reliable than has been claimed.

Genome sequence of Phormia regina Meigen (Diptera: Calliphoridae): implications for medical, veterinary and forensic research

BACKGROUND

Blow flies (Diptera: Calliphoridae) are important medical, veterinary and forensic insects encompassing 8 % of the species diversity observed in the calyptrate insects. Few genomic resources exist to understand the diversity and evolution of this group.

RESULTS

We present the hybrid (short and long reads) draft assemblies of the male and female genomes of the common North American blow fly, Phormia regina (Diptera: Calliphoridae). The 550 and 534 Mb draft assemblies contained 8312 and 9490 predicted genes in the female and male genomes, respectively; including > 93 % conserved eukaryotic genes. Putative X and Y chromosomes (21 and 14 Mb, respectively) were assembled and annotated. The P. regina genomes appear to contain few mobile genetic elements, an almost complete absence of SINEs, and most of the repetitive landscape consists of simple repetitive sequences. Candidate gene approaches were undertaken to annotate insecticide resistance, sex-determining, chemoreceptors, and antimicrobial peptides.

CONCLUSIONS

This work yielded a robust, reliable reference calliphorid genome from a species located in the middle of a calliphorid phylogeny. By adding an additional blow fly genome, the ability to tease apart what might be true of general calliphorids vs. what is specific of two distinct lineages now exists. This resource will provide a strong foundation for future studies into the evolution, population structure, behavior, and physiology of all blow flies.

Survey of the Genetic Diversity of Forensically Important Chrysomya (Diptera: Calliphoridae) from Egypt

Minimum postmortem interval estimations of a corpse using blow fly larvae in medicolegal investigations require correct identification and the application of appropriate developmental data of the identified fly species. Species identification of forensically relevant blow flies could be very difficult and time consuming when specimens are damaged or in the event of morphologically indistinguishable immature stages, which are most common at crime scenes. In response to this, an alternative, accurate determination of species may depend on sequencing and molecular techniques for identification. Chrysomyinae specimens (n = 158) belonging to three forensically important species [Chrysomya albiceps (Wiedemann), Chrysomya megacephala (F.), and Chrysomya marginalis (Wiedemann)] (Diptera: Calliphoridae) were collected from four locations in Egypt (Giza, Dayrout, Minya, and North Sinai) and sequenced across the mitochondrial cytochrome oxidase subunit I (COI) gene. Phylogenetic analyses using neighbor-joining, maximum likelihood and maximum parsimony methods resulted in the same topological structure and confirmed DNA based identification of all specimens. Interspecific divergence between pairs of species was 5.3% (C. marginalis-C. megacephala), 7% (C. albiceps-C. megacephala), and 8% (C. albiceps-C. marginalis). These divergences are sufficient to confirm the utility of cytochrome oxidase subunit I gene in the molecular identification of these flies in Egypt. Importantly, the maximum intraspecific divergence among individuals within a species was <1% and the least nucleotide divergence between species used for phylogenetic analysis was 3.6%. This study highlights the need for thorough and diverse sampling to capture all of the possible genetic diversity if DNA barcoding is to be used for molecular identification.

Verification of AFLP kinship methods of entomological evidence by sequencing

Kinship analysis allows the determination of sibship based on the individuals' genetic profile. In a recent empirical study, amplified fragment length polymorphism (AFLP) analysis was proposed as a test to determine kinship between Phormia regina individuals useful in inferring postmortem transport of a corpse. In order to validate this technique, mitochondrial DNA gene cytochrome oxidase II was sequenced for all individuals used in the previous study. Then, the relatedness coefficient based on AFLP profiles was determined for the pairs of individuals that had different haplotypes, and thus could not be full siblings, to determine a conservative false positive error rate of this proposed test. A majority, 96%, of pair wise comparisons of individuals with different haplotypes had relatedness coefficients <0.41 supporting the conclusion that AFLP analysis for full sibship is a valid and robust technique and thus useful for the detection of postmortem movement of a corpse.

Evaluation of the IrisPlex DNA-based eye color prediction assay in a United States population

DNA phenotyping is a rapidly developing area of research in forensic biology. Externally visible characteristics (EVCs) can be determined based on genotype data, specifically based on single nucleotide polymorphisms (SNPs). These SNPs are chosen based on their association with genes related to the phenotypic expression of interest, with known examples in eye, hair, and skin color traits. DNA phenotyping has forensic importance when unknown biological samples at a crime scene do not result in a criminal database hit; a phenotypic profile of the sample can therefore be used to develop investigational leads. IrisPlex, an eye color prediction assay, has previously shown high prediction rates for blue and brown eye color in a Dutch European population. The objective of this work was to evaluate its utility in a North American population. We evaluated six SNPs included in the IrisPlex assay in population sample collected from a USA college campus. We used a quantitative method of eye color classification based on (RGB) color components of digital photographs of the eye taken from each study volunteer so that each eye was placed in one of three eye color categories: brown, intermediate, or blue. Objective color classification was shown to correlate with basic human visual determination making it a feasible option for use in future prediction assay development. Using these samples and various models, the maximum prediction accuracies of the IrisPlex system after allele frequency adjustment was 58% and 95% brown and blue eye color predictions, respectively, and 11% for intermediate eye colors. Future developments should include incorporation of additional informative SNPs, specifically related to the intermediate eye color, and we recommend the use of a Bayesian approach as a prediction model as likelihood ratios can be determined for reporting purposes.

Increasing precision in development-based postmortem interval estimates: what's sex got to do with it?

Forensic entomologists typically use either succession models for postmortem interval (PMI) estimates or development-based models for minimum PMI (PMI(MIN) estimates. Development-based age estimates are calculated with durations of immature stadia and can also include morphological data such as larval size. For developmental data, the first and second instar stages are typically brief with little variation in larval length. The third instar, a much longer stage by comparison, is prone to considerable variation. This variation is, in part, because of the nonlinear growth during the third instar. There is evidence that genetic and environmental factors influence growth curve divergence during this stage. We chose to investigate one genetic factor, sex, as numerous insect species exhibit sex-specific immature growth patterns. The development rate of Lucilia sericata (Meigen) (Diptera: Calliphoridae) males and females is considered here. We previously determined the genome sizes of L. sericata and found significant sexually dimorphic genome sizes. This difference can be exploited to identify larval sex to evaluate male and female immature growth curves. A preliminary development study encompassing the third larval instar was conducted to compare larval lengths for each sex. Results showed length (P < 0.0001) and sex (P < 0.01) were statistically significant predictors of age at two temperatures (30 and 33.5 degrees C), and that total male development was significantly shorter (P < 0.001). These results introduce a new tool, assessment of sex-specific growth, that has the potential to reduce noise in PMI(MIN) estimates when using third instar larvae.

Amplified fragment length polymorphism confirms reciprocal monophyly in Chrysomya putoria and Chrysomya chloropyga: a correction of reported shared mtDNA haplotypes

Reinvestigation of mitochondrial haplotypes previously reported to be shared between the Afrotropical blowflies Chrysomya putoria Weidemann and Chrysomya chloropyga Weidemann (Diptera: Calliphoridae) revealed an error resulting from the misidentification of specimens. Preliminary amplified fragment length polymorphism (AFLP) analysis of the original and additional individuals again failed to find reciprocal monophyly, leading to a re-examination of the specimens for diagnostic male genitalic characters that were first described following the earlier study. Four of the original study specimens were found to have been misidentified, and definitive analysis of both mtDNA and AFLP genotypes using phylogenetic analysis and genetic assignment showed that each species was indeed reciprocally monophyletic. In addition to correcting the earlier error, this study illustrates how AFLP analysis can be used for efficient and effective specimen identification through both phylogenetic analysis and genetic assignment, and suggests that the latter method has special advantages for identification when no conspecific specimens are represented in the reference database.

Genome sizes of forensically relevant Diptera

Genome size estimates for both sexes of forensically relevant Diptera from 17 species (four families) are reported herein. Average genome sizes ranged from 425.8 Mb for female Chrysomya rufifacies to 1,197.4 Mb for male Haematobia irritans. These estimates are useful not only for molecular studies, but also for determination of the species and sex of immatures. Species in three of the sampled families had sexually dimorphic genome sizes, presenting a new tool useful for the determination of sex in these species, especially in the immature stages where sexes are morphologically difficult or impossible to identify. In addition, closely related species had significantly different genome sizes, suggesting the use of flow cytometry as a new tool for species identification of some species of forensically relevant larvae.

Population and temperature effects on Lucilia sericata (Diptera: Calliphoridae) body size and minimum development time

Understanding how ecological conditions influence physiological responses is fundamental to forensic entomology. When determining the minimum postmortem interval with blow fly evidence in forensic investigations, using a reliable and accurate model of development is integral. Many published studies vary in results, source populations, and experimental designs. Accordingly, disentangling genetic causes of developmental variation from environmental causes is difficult. This study determined the minimum time of development and pupal sizes of three populations of Lucilia sericata Meigen (Diptera: Calliphoridae; from California, Michigan, and West Virginia) at two temperatures (20 degrees C and 33.5 degrees C). Development times differed significantly between strain and temperature. In addition, California pupae were the largest and fastest developing at 20 degrees C, but at 33.5 degrees C, though they still maintained their rank in size among the three populations, they were the slowest to develop. These results indicate a need to account for genetic differences in development, and genetic variation in environmental responses, when estimating a postmortem interval with entomological data.

Survey of the genetic diversity of Phormia regina (Diptera: Calliphoridae) using amplified fragment length polymorphisms

There is very little information concerning carrion fly population genetic structure. We generated amplified fragment length polymorphism (AFLP) profiles for the common blowfly, Phormia regina (Meigen), from sites spanning the contiguous United States. Analysis of molecular variance (AMOVA) based on 232 loci found significant variation (phi(SC) = 23%) among discrete samples (those collected at a bait in one location over a short period of time). Samples collected in the same location but at different times were also distinct. When samples were pooled into geographic regions (east, central, west), the variation was negligible (phi(CT) = 0%). A Mantel test found only a very weak correlation between individual genetic and geographic distances. Relative relatedness coefficients based on shared allele proportions indicated individual samples were likely to contain close relatives. P. regina arriving at an individual carcass typically represent a nonrandom sample of the population despite a lack of geographic structure. A female blow fly produces hundreds of offspring at one time; therefore, newly emerged siblings may respond in concert to an odor plume. These results may be of interest to forensic entomologists, many of whom use a laboratory colony founded from a small sample for the growth studies that support casework. Discrepancies between published growth curves may reflect such random differences in the founding individuals.

Development of Electrochemical Processes for Nitrene Generation and Transfer

An electrochemical strategy for running nitrogen-transfer reactions on chemically inert anode surfaces has been developed. The generation and trapping of highly reactive nitrene-transfer reagents can be accomplished under mild conditions on platinum electrodes. The key factor that accounts for the high levels of chemoselectivity in this process is the phenomenon of overpotential. We have found that molecules that are similar in terms of propensity toward oxidation can be differentiated on the basis of their affinity to a given electrode surface. Thereby, reactive species can be selectively generated in the presence of acceptor molecules of interest. Specifically, a wide range of structurally dissimilar olefins can be transformed into the corresponding aziridines in the presence of N-aminophthalimide. Likewise, nitrene generation in the presence of sulfoxides leads to their chemoselective transformation into the corresponding sulfoximines. In this paper we discuss the underlying mechanistic foundation of these reactions.