Ian R. Dadour

Mitochondrial DNA cytochrome oxidase I gene: potential for distinction between immature stages of some forensically important fly species (Diptera) in western Australia

Forensic entomology requires the fast and accurate identification of insects collected from a corpse for estimation of the postmortem interval (PMI). Identification of specimens is traditionally performed using morphological features of the insect. Morphological identification may be complicated however by the numerical diversity of species and physical similarity between different species, particularly in immature stages. In this study, sequencing was performed to study the mitochondrial DNA (mtDNA) as the prospective basis of a diagnostic technique. The sequencing focused on a section of the cytochrome oxidase I encoding region of mtDNA. Three species of calliphorid (blow flies) commonly associated with corpses in western Australia, Calliphora dubia, Chrysomya rufifacies and Lucilia sericata, in addition to specimens of Calliphora augur and Chrysomya megacephala were studied. Phylogenetic analysis of data revealed grouping of species according to genus. The DNA region sequenced allowed identification of all species, providing high support for separation on congeneric species. Low levels of variation between some species of the same genus however indicate that further sequencing is required to locate a region for development of a molecular-based technique for identification.

Molecular identification of some forensically important blowflies of southern Africa and Australia

Abstract.  One major aspect of research in forensic entomology is the investigation of molecular techniques for the accurate identification of insects. Studies to date have addressed the corpse fauna of many geographical regions, but generally neglected the southern African calliphorid species. In this study, forensically significant calliphorids from South Africa, Swaziland, Botswana and Zimbabwe and Australia were sequenced over an 1167 base pair region of the COI gene. Phylogenetic analysis was performed to examine the ability of the region to resolve species identities and taxonomic relationships between species. Analyses by neighbour‐joining, maximum parsimony and maximum likelihood methods all showed the potential of this region to provide the necessary species‐level identifications for application to post‐mortem interval (PMI) estimation; however, higher level taxonomic relationships did vary according to method of analysis. Intraspecific variation was also considered in relation to determining suitable maximum levels of variation to be expected during analysis. Individuals of some species in the study represented populations from both South Africa and the east coast of Australia, yet maximum intraspecific variation over this gene region was calculated at 0.8%, with minimum interspecific variation at 3%, indicating distinct ranges of variation to be expected at intra‐ and interspecific levels. This region therefore appears to provide southern African forensic entomologists with a new technique for providing accurate identification for application to estimation of PMI.

A global study of forensically significant calliphorids: implications for identification.

A proliferation of molecular studies of the forensically significant Calliphoridae in the last decade has seen molecule-based identification of immature and damaged specimens become a routine complement to traditional morphological identification as a preliminary to the accurate estimation of post-mortem intervals (PMI), which depends on the use of species-specific developmental data. Published molecular studies have tended to focus on generating data for geographically localised communities of species of importance, which has limited the consideration of intraspecific variation in species of global distribution. This study used phylogenetic analysis to assess the species status of 27 forensically important calliphorid species based on 1167 base pairs of the COI gene of 119 specimens from 22 countries, and confirmed the utility of the COI gene in identifying most species. The species Lucilia cuprina, Chrysomya megacephala, Ch. saffranea, Ch. albifrontalis and Calliphora stygia were unable to be monophyletically resolved based on these data. Identification of phylogenetically young species will require a faster-evolving molecular marker, but most species could be unambiguously characterised by sampling relatively few conspecific individuals if they were from distant localities. Intraspecific geographical variation was observed within Ch. rufifacies and L. cuprina, and is discussed with reference to unrecognised species.

Sexual Dimorphism in the Subadult Mandible: Quantification Using Geometric Morphometrics

ABSTRACT: There have been numerous attempts, with varying degrees of success, to differentiate males from females on the basis of the immature skeleton. We investigate here whether the mandible can discriminate immature individuals by sex; the techniques we apply are from the field of geometric morphometrics. The application of these methods in forensic anthropology is still relatively new; thus, an important aspect of this research is that it demonstrates potential applications in this discipline. The sample comprises 96 known age and sex subadult individuals; the three‐dimensional coordinates of 38 landmarks are analyzed using the shape analysis software morphologika. Multivariate regressions indicated no significant sexual dimorphism in the subadult sample; this result is supported by poor cross‐validated classification accuracy (59%). Our results suggest that the subadult mandible is not dimorphic (to the extent that dimorphism is not evident within the sample we studied); thus, sex determination using previously described criteria is likely to yield poor results.

Annual and seasonal patterns of insect succession on decomposing remains at two locations in Western Australia

This study considered annual, seasonal and shorter term variation in patterns of insect succession onto decomposing remains at two contrasting locations in Western Australia, bushland and agricultural. The degree of consistency in insect succession patterns over spatial and temporal scales was evaluated through multivariate analysis of occurrence-based distance matrices. Insect assemblages were strongly correlated between locations, within corresponding time periods, indicating that patterns of insect succession were similar between localised sites within the same broad geographic area. This suggests that there is reasonable scope for the application of baseline succession data generated at a single study site to a range of decomposition sites within a given region. Differences were largely due to species absences at the agricultural site. Three species of Coleoptera were identified as possible representatives of bushland habitat, Ptomaphila lacrymosa (Silphidae), Omorgus tatei (Trogidae) and Helea castor (Tenebrionidae), and may be indicative of post mortem movement between habitat types. Within locations, variation in insect assemblages was not significant between years. Within years, insect assemblages varied significantly over time on a seasonal time scale and as decomposition progressed through defined decomposition stages. Forensically relevant data detailing the seasonal pattern of insect succession onto decomposing remains for Western Australia are reported. Additional focus has been directed towards hymenopteran parasitoids that frequent decomposing remains and parasitise Diptera colonisers. Parasitoids can be used to provide an extended PMI timeframe in cases where traditional forensic indicators have completed their development.

A preliminary investigation of the stages of adipocere formation.

Adipocere is a postmortem decomposition product which forms from a bodys adipose tissue. This study aimed to chemically demonstrate the process of conversion from adipose tissue to adipocere. Samples of adipocere were collected from pig cadavers that were allowed to decompose for varying intervals. Samples of soil were collected from beneath the cadavers and analyzed to determine the leaching effect of adipocere. Gas chromatography/mass spectrometry (GC/MS) was used to quantify the fatty acid composition of pig adipocere. Fourier transform infrared spectroscopy (FTIR) was used as a confirmatory test and to identify other components such as triglycerides and calcium salts of fatty acids. The study demonstrates the process of adipocere formation and the stages of formation through which the process passes using chemical techniques.

Discriminant function sexing of the mandible of Indigenous South Africans

South Africa currently has a high homicide rate. This results in a large number of unidentified bodies being recovered each year, many of which are referred to the forensic examiner. This situation has resulted in considerable growth of forensic anthropological research devoted to devising standards for specific application in South African medico-legal investigations. The standards suitable for Black South Africans now encompass a wide variety of skeletal elements (e.g. cranium, humerus, pelvis, femur, patella, talus, calcaneus), each with differing degrees of accuracy. Apart from a preliminary investigation of the Zulu local population, however, we note that there appears to be no established metric mandible discriminant function standards for sex determination in this population. The purpose of the present study is to undertake a comprehensive analysis of sexual dimorphism in the mandible of Black South Africans, incorporating individuals from a selection of the larger local population groupings; the primary aim is to produce a series of metrical standards for the determination of sex. The sample analyzed comprises 225 non-pathological mandibles of Black South African individuals drawn from the R.A. Dart Collection. Nine linear measurements, obtained from mathematically transformed three-dimensional landmark data, are analyzed using basic univariate statistics and discriminant function analyses. All of the measurements examined are found to be sexually dimorphic; the dimensions of the ramus and corpus lengths are most dimorphic. The sex classification accuracy of the discriminant functions ranged from 70.7 to 77.3% for the univariate method, 81.8% for the stepwise method, and 63.6 to 84% for the direct method. We conclude that the mandible is a very useful element for sex determination in this population.

Effect of diet on the excretion profile of ivermectin in cattle faeces

Two groups of 26 cattle (cross-bred, 3-8 years old, weight 450-650 kg) were placed onto 2 feed regimens, pasture-fed and grain-fed. The pasture-fed cattle were kept on irrigated pasture with hay supplement ad libitum, whereas the grain-fed cattle were kept in a feedlot and fed hay and lupin grain in a 40:60 ratio. Half the cattle within each feed group (n = 13) were given a subcutaneous injection of ivermectin (Ivomec) at the dose rate of 200 micrograms/kg liveweight. Over 5 times higher levels of ivermectin were excreted in the faeces of grain-fed cattle compared with pasture-fed (grazing) cattle. Peak excretion levels of 0.36 mg/kg (grain-fed) and 0.09 mg/kg (pasture-fed) of ivermectin were recorded at 6 and 8 days post-injection (dpi), respectively. Ivermectin was detected in faeces for up to 13 dpi (grain-fed) and 14 dpi (pasture-fed). Faecal pH in grain-fed cattle was more acidic (6.43) compared with pasture-fed cattle (7.28) and the levels of nitrogen in faeces from grain-fed cattle were higher (0.42%) compared with pasture-fed cattle (0.20%). Treatment with ivermectin had no influence on either the pH or nitrogen levels of faeces from either feed regimen. The impact of diet on the excretion profile of ivermectin is discussed in the context of studies attempting to demonstrate ecotoxic effects of ivermectin residues in cattle faeces on dung beetles.

Forensic entomology: application, education and research in Western Australia.

Forensic entomology as a science and a tool for investigation has had slow beginnings in Australia. A number of small animal decomposition trials have been recorded in the literature but mostly from an ecological rather than a forensic entomology perspective. In the last 20 years, a number of more forensically orientated field trials on small pigs and some fly developmental trials in the laboratory have been conducted but lack any replication. The following article was presented at an international seminar to detail the current research in forensic entomology, the applications of forensic entomology in scene of crime (SOC) and homicide investigations and the education of police and judiciary in the discipline of forensic entomology in Western Australia over the last 10 years.

determination of sex in south african blacks by discriminant function analysis of mandibular linear dimensions

The determination of sex is a critical component in forensic anthropological investigation. The literature attests to numerous metrical standards, each utilizing diffetent skeletal elements, for sex determination in South A frican Blacks. Metrical standards are popular because they provide a high degree of expected accuracy and are less error-prone than subjective nonmetric visual techniques. We note, however, that there appears to be no established metric mandible discriminant function standards for sex determination in this population.We report here on a preliminary investigation designed to evaluate whether the mandible is a practical element for sex determination in South African Blacks. The sample analyzed comprises 40 nonpathological Zulu individuals drawn from the R.A. Dart Collection. Ten linear measurements, obtained from mathematically trans-formed three-dimensional landmark data, are analyzed using basic univariate statistics and discriminant function analyses. Seven of the 10 measurements examined are found to be sexually dimorphic; the dimensions of the ramus are most dimorphic. The sex classification accuracy of the discriminant functions ranged from 72.5 to 87.5% for the univariate method, 92.5% for the stepwise method, and 57.5 to 95% for the direct method. We conclude that the mandible is an extremely useful element for sex determination in this population.