Molecular identification of forensically important fly species in Spain using COI barcodes

Molecular identification and genetic variation of forensically important fly species (Order: Diptera) in Thailand using DNA barcoding

Forensic entomology plays a crucial role in criminal investigations by providing vital insights into minimum postmortem interval (PMImin) and corpse relocation by identifying insect species that colonize in decomposing remains. This study aimed to identify and analyze the genetic variation of forensically significant fly species in Thailand, using DNA barcoding of the mitochondrial cytochrome c oxidase subunit I COI gene. A total of 3,220 fly specimens were collected from 18 provinces across six regions of Thailand from October 2017 to September 2022. These specimens were classified by morphological identification into 21 species among three Dipteran families: Calliphoridae, Muscidae, and Sarcophagidae, with Chrysomya megacephala Diptera: Calliphoridae being the most abundant species. DNA barcoding confirmed the morphological identifications with 100 % accuracy, showing low intraspecific K2P distances0.0 to 1.1 %) and significant interspecific K2P distances 2.5 % to 17.2 %. A Neighbour-Joining (NJ) analysis was conducted to assess the molecular identification capabilities of the barcoding region. This analysis successfully recovered nearly all species as distinct monophyletic groups. The species groupings obtained were generally consistent with both morphological and molecular identifications. These findings underscore the effectiveness of DNA barcoding for precise species identification and contribute to a comprehensive database of forensically important flies in Thailand, thus facilitating improved forensic investigations and biodiversity studies.

The influence of altitude on the abundance and occurrence of species of the family Calliphoridae (Diptera) in corpses in a Mediterranean area

A carcass is defined as a temporary resource that can support high levels of diversity compared to other resources. The level of diversity often depends on the environmental conditions in which the corpse is found. Calliphoridae (Diptera) are the most important necrophagous insects used in forensic investigations because this family is common, widespread, abundant, and usually the first to colonize a corpse. However, understanding the processes responsible for variation in calliphorid species abundance and richness along gradients in ecology remains a key challenge. In this study, we analyzed the influence of altitude on the abundance and diversity of Calliphoridae species in corpses at three different altitudes (400, 900, and 1500 m a.s.l.) in a mountainous area of southeastern Spain. The results revealed a gradient of decreasing abundance with increasing altitude. An altitudinal substitution of species was observed, with Chrysomya albiceps being found at the lowest altitude and Calliphora vicina at the highest altitude. Seasonal variation was also noted, with Ch. albiceps being the dominant species in the warmer months and C. vicina being the dominant species in winter. Our results confirm the importance of Calliphorids as seasonal, altitudinal, and environmental indicators, given the wide distribution and abundance of this family. This information is of great interest on the interpretation of data in forensic practice.

Geographical Distribution and Multimethod Species Identification of Forensically Important Necrophagous Flies on Hainan Island

Forensic entomology offers unique advantages for the minimum postmortem interval (PMImin) estimation of decomposed corpses in forensic investigations. Accurate species identification and up-to-date locality information are essential. Hainan Island has a tropical rainforest climate and a vast territory. In this study, the community structure of necrophagous flies on Hainan Island was investigated in detail according to geographical environment. The results showed that the dominant species included C. megacephala, S. peregrina, C. rufifacies, S. misera, H. ligurriens, S. sericea, S. cinerea, S. dux, C. pinguis, and M. domestica. Furthermore, C. rufifacies and C. villeneuvi were found only in the high-altitude areas of Wuzhi Mountain, while S. cinerea was distributed only in coastal areas; the latter is a representative species of Hainan Island and has not been reported before. Furthermore, a GenBank database of forensically important flies was established, whilst a high-resolution melt (HRM) curve analysis was applied to identify the common species of Hainan Island for the first time. This study enriches the database of forensically important flies in tropical rainforest regions.

A DNA-based method for distinction of fly artifacts from human bloodstains

Fly artifacts resulting from insect activity could act as confounding factors on a crime scene and interfere with bloodstain pattern analysis interpretation. Several techniques have been proposed to distinguish fly artifacts from human bloodstains based on morphological approach and immunological assay, but a DNA-based method has not been developed so far. Even if in forensic genetic investigations the detection of human DNA is generally the primary goal, fly artifacts can provide useful information on the dynamics of crime events. The present study provides a molecular method to detect fly DNA from artifacts deposited by Calliphora vomitoria after feeding on human blood through the analysis of the mitochondrial cytochrome oxidase gene subunit I (COI). Fly artifacts originated from digestive process and of different morphology spanning from red and brownish/light brown, circular and elliptical stains to artifacts with sperm-like tail or a tear-shaped body were collected. The COI amplification was successfully obtained in 94% of fly artifact samples. The method showed high sensitivity and reproducibility, and no human DNA contamination was observed, offering specificity for use in confirmatory test. This molecular approach permits the distinction of fly artifacts from genuine bloodstains and the identification of fly's species through the COI region sequencing by protocols usually applied in forensic genetic laboratories.

DNA-based and taxonomic identification of forensically important Sarcophagidae (Diptera) in southeastern Spain

Studying dipterans at the scene of a death can provide essential information for interpreting the evidence and help to reconstruct the events happened to a corpse in the past. Molecular tools have been employed for identification at specific levels in the cases of cryptic species or poorly conserved specimens. Identification of specimens is essential in forensic entomology since each species has a specific growth rate, which determines the calculation of the minimum post mortem interval (minPMI). In addition, phylogeographic reconstruction within a species can help to differentiate the haplotypes from a geographic area, thereby helping to clarify the possible relocation of a corpse. The morphological identification of Sarcophagidae species is often difficult, especially for the females. This is an important Diptera family since some of its species are among the first to reach a corpse, especially in warm areas. In this study, we compared the sarcophagids found in human corpses in forensic cases in Alicante (southeast of Spain) with specimens collected from baited traps in the same area and surrounding provinces. In total, 189 specimens were collected, comprising 72 from forensic cases and 117 from baited traps. Molecular identification was conducted by sequencing the cox1 mitochondrial gene and analyzing the sequences using ABGD, GMYC, and BIN species delimitation methods. The median joining algorithm in the PopART program was used to construct phylogeographic networks. Eight species in the family Sarcophagidae were identified. The most widely collected species were Sarcophaga argyrostoma and Sarcophaga tibialis. The haplotype networks obtained for these species did not indicate a clear geographic distribution of haplotypes. The S. argyrostoma samples from Alcoy were clearly isolated. The results demonstrated that this method is useful for identifying Sarcophagidae samples in forensic investigations and it can be employed for minPMI estimation.

Genetic diversity of Calliphora vicina (Diptera: Calliphoridae) in the Iberian Peninsula based on cox1, 16S and ITS2 sequences

The study of Diptera at the scene of a crime can provide essential information for the interpretation of evidence. Phylogeographic reconstruction could help differentiate haplotypes of a dipteran species in a geographical area, clarifying, for example, the details of a possible relocation of a corpse. In addition, inferring the ancestral areas of distribution helps to understand the current status of the species and its biogeographic history. One of the most important species in forensic entomology is Calliphora vicina Rovineau-Desvoidy, 1830 (Diptera: Calliphoridae). The aim of this work is to increase our knowledge of this species in the Iberian Peninsula using 464 specimens from Spain and Portugal. These samples were identified using morphological keys and by molecular methods using fragments of the cox1, 16S and ITS2 genes. The phylogeographic history of these populations was inferred from haplotype networks and the reconstruction of ancestral areas of distribution. The molecular results corroborated the morphological identifications of the samples. Phylogeographic networks showed no geographical structure, as haplotypes are shared among almost all populations. reconstruct ancestral state in phylogenies analyses showed a high rate of movement among populations, possibly related to human activity. These results suggest that this species had a very rapid and recent spatial and demographic expansion throughout the Iberian Peninsula.

A world review of reported myiases caused by flower flies (Diptera: Syrphidae), including the first case of human myiasis from Palpada scutellaris (Fabricius, 1805)

Rat-tailed larvae of the syrphid species Palpada scutellaris (Fabricius, 1805) are documented causing an enteric human myiasis in Costa Rica. This is the first time that the genus Palpada is recorded as a human myiasis agent. We report a 68-year-old woman with intestinal pain and bloody diarrhea with several live Palpada larvae present in the stool. Using molecular techniques (DNA barcodes) and both electronic and optical microscopy to study the external morphology, the preimaginal stages of the fly were unambiguously identified. An identification key to all syrphid genera actually known as agents of human and animal myiases is provided for larvae, puparia, and adults. Moreover, a critical world review of more than 100 references of Syrphidae as myiasis agents is also given, with emphasis on the species with rat-tailed larvae.