Abstract
Flesh flies (Sarcophagidae) are necrophagous insects initially colonizing on a corpse. The species-specific developmental data of the flies collected from a death scene can be used to estimate the minimum postmortem interval (PMImin). Thus, the first crucial step is to correctly identify the fly species. Because of the high similarity among species of flesh flies, DNA-based identification is considered more favorable than morphology-based identification. In this study, we demonstrated the effectiveness of combined sequences (2216 to 2218 bp) of cytochrome c oxidase subunit I and II genes (COI and COII) for identification of the following 14 forensically important flesh fly species in Thailand: Boettcherisca nathani Lopes, Fengia ostindicae (Senior-White), Harpagophalla kempi (Senior-White), Liopygia ruficornis (Fabricius), Lioproctia pattoni (Senior-White), Lioproctia saprianovae (Pape & Bänziger), Parasarcophaga albiceps (Meigen), Parasarcophaga brevicornis (Ho), Parasarcophaga dux (Thomson), Parasarcophaga misera (Walker), Sarcorohdendorfia antilope (Böttcher), Sarcorohdendorfia inextricata (Walker), Sarcorohdendorfia seniorwhitei (Ho) and Seniorwhitea princeps (Wiedemann). Nucleotide variations of Thai flesh flies were evenly distributed throughout the COI-COII genes. Mean intra- and interspecific variations ranged from 0.00 to 0.96% and 5.22% to 12.31%, respectively. Using Best Match (BM) and Best Close Match (BCM) criteria, identification success for the combined genes was 100%, while the All Species Barcodes (ASB) criterion showed 76.74% success. Maximum Likelihood (ML) and Bayesian Inference (BI) phylogenetic analyses yielded similar tree topologies of monophyletic clades between species with very strong support values. The achieved sequences covering 14 forensically important flesh fly species including newly submitted sequences for B. nathani, F. ostindicae and S. seniorwhitei, can serve as a reliable reference database for further forensic entomological research in Thailand and in other areas where those species occur.
Highlights
Wing morphometric analysis has been applied for species and sex discrimination of flesh flies in Thailand [39]
Only two genetic studies of forensically relevant flesh flies have been reported from Thailand
The results showed that the correct identification obtained by the short c oxidase subunit I (COI) sequences of 127 bp (80.7% to 82.5%) was lower than that of the standard COI (658 bp) or entire COI (1535 bp) (98.2% to 99.3%) regions
Summary
Besides the Calliphoridae, Sarcophagidae (flesh flies) contain some of the most important carrion-breeding flies which colonize a human cadaver during the initial stages of decomposition [1].In forensic investigations, the sarcophagids provide more precise PMImin estimation than calliphorids because they are larviparous and deposit larvae directly on the cadaver and feed immediately [2].Substantial entomological evidence has been presented for flesh flies, for example, Bercaea africa (Wiedemann) in Italy [3], Liopygia ruficornis (Fabricius) in Thailand [4] and Kuwait [5], B. africa, Parasarcophaga dux (Thomson), Liopygia argyrostoma (Robineau-Desvoidy), Robineauella scoparia (Pandelle), Parasarcophaga similis (Meade) in Switzerland [6], Seniorwhitea princeps (Wiedemann) in Malaysia [7], and L. argyrostoma, B. africa, Heteronychia fertoni (Villeneuve), Boettcherisca peregrine (Robineau-Desvoidy) in Iran [8,9].Among 2510 known species in 173 genera of Sarcophagidae described worldwide [10], 86 species in 31 genera have been recorded in Thailand [11]. Besides the Calliphoridae, Sarcophagidae (flesh flies) contain some of the most important carrion-breeding flies which colonize a human cadaver during the initial stages of decomposition [1]. In forensic investigations, the sarcophagids provide more precise PMImin estimation than calliphorids because they are larviparous and deposit larvae directly on the cadaver and feed immediately [2]. Among 2510 known species in 173 genera of Sarcophagidae described worldwide [10], 86 species in 31 genera have been recorded in Thailand [11]. Morphological characteristics of immature and adult stages among flesh fly species are very similar, making identification difficult, for non-expert taxonomists [13]. Since the developmental times of flesh flies are species specific, the correct identification at the species level is a primary step for estimating the PMImin [14,15]
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