Comparative analysis of mitochondrial genomes among four species of muscid flies (Diptera: Muscidae) and its phylogenetic implications

Application of omics techniques in forensic entomology research

With the advent of the post-genome era, omics technologies have developed rapidly and are widely used, including in genomics, transcriptomics, proteomics, metabolomics, and microbiome research. These omics techniques are often based on comprehensive and systematic analysis of biological samples using high-throughput analysis methods and bioinformatics, to provide new insights into biological phenomena. Currently, omics techniques are gradually being applied to forensic entomology research and are useful in species identification, phylogenetics, screening for developmentally relevant differentially expressed genes, and the interpretation of behavioral characteristics of forensic-related species at the genetic level. These all provide valuable information for estimating the postmortem interval (PMI). This review mainly discusses the available omics techniques, summarizes the application of omics techniques in forensic entomology, and their future in the field.

Contribution to the Knowledge of Dicranoptychini (Diptera, Tipuloidea, Limoniidae) in China, with the First Mitochondrial Genome of the Tribe and Its Phylogenetic Implications

Dicranoptychini is a tribe in the subfamily Limoniinae (Diptera, Tipuloidea, and Limoniidae) and includes only the genus Dicranoptycha Osten Sacken, 1860. However, the species diversity of the tribe in China was seriously underestimated, and the taxonomic status of Dicranoptycha has long been controversial. In this study, types of Chinese Dicranoptycha species and specimens collected from several localities in China were examined, and the first mitochondrial (mt) genome of the tribe Dicranoptychini is presented. Two Dicranoptycha species, D. jiufengshana sp. nov. and D. shandongensis sp. nov., from China, are described and illustrated as new to science. A Palaearctic species, D. prolongata Alexander, 1938, is recorded in China for the first time. In addition, the complete mt genome of D. shandongensis sp. nov. is sequenced and annotated, indicating that it is a typical circular DNA molecule with a length of 16,157 bp and shows a similar gene order, nucleotide composition, and codon usage to mt genomes of other Tipuloidea species. The two pairs of repeat elements are found in its control region. Phylogenetic results confirm the sister-group relationship between Cylindrotomidae and Tipulidae, question the position of the genus Epiphragma Osten Sacken, 1860 in Limoniidae, and indicate that Dicranoptychini may be a basal lineage within Limoniinae.

Phylogeny and Evolutionary Timescale of Muscidae (Diptera: Calyptratae) Inferred from Mitochondrial Genomes

House flies (Muscidae) comprise the most species-rich family of the muscoid grade with over 5000 described species worldwide, and they are abundant in various terrestrial and aquatic ecosystems. The high number of species, varied appearances, complex feeding habits, and wide distributions have hindered researchers from understanding their phylogeny and evolutionary history. Here, we newly sequenced fifteen mitochondrial genomes and reconstructed the phylogenetic relationships and divergence time among eight subfamilies of Muscidae (Diptera). The best phylogenetic tree, which was inferred by IQ-Tree, recovered the monophyly for seven out of eight subfamilies (except for Mydaeinae). Based on phylogenetic analyses and morphological characteristics, we prefer the subfamily status of Azeliinae and Reinwardtiinae, and separate Stomoxyinae from Muscinae. Genus Helina Robineau-Desvoidy, 1830 was synonymized with Phaonia Robineau-Desvoidy, 1830. The divergence time estimation indicated Muscidae originated at 51.59 Ma (early Eocene). Most subfamilies had originated around 41 Ma. We provided a mtgenomic viewpoint on the phylogenetic relationships and divergence time estimation of Muscidae.

Phylogenetic Analysis of Mitochondrial Genome of Tabanidae (Diptera: Tabanidae) Reveals the Present Status of Tabanidae Classification

Simple Summary

Tabanidae suck the blood of humans and animals, are important biological vectors for the transmission of diseases, and are of considerable economic and medical significance. However, current knowledge about the mitochondrial genome of this family is limited. Therefore, six newly completed mitochondrial genomes of four genera of Tabanidae (Haematopota turkestanica, Chrysops vanderwulpi, Chrysops dissectus, Tabanus chrysurus, Tabanus pleskei, and Hybomitra sp. species) were sequenced and analyzed. The results show that the six newly mitochondrial genomes have quite similar structures and features. Phylogeny was inferred by analyzing the 13 amino acid sequences coded by mitochondrial genes of 22 mitogenomes (all available complete mitochondrial genomes of tabanidae). Bayesian inference, maximum likelihood trees, and maximum parsimony inference analyses all showed consistent results. This study supports the concept of monophyly of all groups, ratifies the current taxonomic classification, and provides useful genetic markers for studying the molecular ecology, systematics, and population genetics of Tabanidae.

Abstract

Tabanidae suck the blood of humans and animals, are important biological vectors for the transmission of diseases, and are of considerable economic and medical significance. However, current knowledge about the mitochondrial genome of this family is limited. More complete mitochondrial genomes of Tabanidae are essential for the identification and phylogeny. Therefore, this study sequenced and analyzed six complete mitochondrial (mt) genome sequences of four genera of Tabanidae for the first time. The complete mt genomes of the six new sequences are circular molecules ranging from 15,851 to 16,107 base pairs (bp) in size, with AT content ranging from 75.64 to 77.91%. The six complete mitochondrial genomes all consist of 13 protein-coding genes (PCGs), 2 ribosomal RNA genes (RRNA), 22 transfer RNA genes (tRNAs), and a control region, making a total of 37 functional subunits. ATT/ATG was the most common start codon, and the stop codon was TAA of all PCGS. All tRNA except tRNA Ser1 had a typical clover structure. Phylogeny was inferred by analyzing the 13 concatenated amino acid sequences of the 22 mt genomes. Bayesian inference, maximum-likelihood trees, and maximum-parsimony inference analyses all showed consistent results. This study supports the concept of monophyly of all genus, ratifies the current taxonomic classification, and provides effective genetic markers for molecular classification, systematics, and genetic studies of Tabanidae.

Comparative Mitogenome Analysis of Gerbils and the Mitogenome Phylogeny of Gerbillinae (Rodentia: Muridae)

To enrich the mitogenomic database of Gerbillinae (Rodentia: Muridae), mitogenomes of three gerbils from different genera, Meriones tamariscinus (16,393 bp), Brachiones przewalskii (16,357 bp), and Rhombomys opimus (16,352 bp), were elaborated and compared with those of other gerbils in the present study. The three gerbil mitogenomes consisted of 2 ribosomal RNA genes, 13 protein-coding genes (PCGs), 22 transfer RNA genes, and one control region. Here, gerbil mitogenomes have shown unique characteristics in terms of base composition, codon usage, non-coding region, and the replication origin of the light strand. There was no significant correlation between the nucleotide percentage of G + C and the phylogenetic status in gerbils, and between the GC content of PCGs and the leucine count. Phylogenetic relationships of the subfamily Gerbillinae were reconstructed by 7 gerbils that represented four genera based on concatenated mitochondrial DNA data using both Bayesian Inference and Maximum Likelihood. The phylogenetic analysis indicated that M. tamariscinus was phylogenetically distant from the genus Meriones, but has a close relationship with R. opimus. B. przewalskii was closely related to the genus Meriones rather than that of R. opimus.

Characterization and Comparative Analysis of Mitochondrial Genomes Among the Calliphoridae (Insecta: Diptera: Oestroidea) and Phylogenetic Implications

The Calliphoridae (blowflies) are significant for forensic science, veterinary management, medical science, and economic issues. However, the phylogenetic relationships within this family are poorly understood and controversial, and the status of the Calliphoridae has been a crucial problem for understanding the evolutionary relationships of the Oestroidea these years. In the present study, seven mitochondrial genomes (mitogenomes), including six calliphorid species and one Polleniidae species, were sequenced and annotated. Then a comparative mitochondrial genomic analysis among the Calliphoridae is presented. Additionally, the phylogenetic relationship of the Calliphoridae within the larger context of the other Oestroidea was reconstructed based on the mitogenomic datasets using maximum likelihood (ML) and Bayesian methods (BI). The results suggest that the gene arrangement, codon usage, and base composition are conserved within the calliphorid species. The phylogenetic analysis based on the mitogenomic dataset recovered the Calliphoridae as monophyletic and inferred the following topology within Oestroidea: (Oestridae (Sarcophagidae (Calliphoridae + (Polleniidae + (Mesembrinellidae + Tachinidae))))). Although the number of exemplar species is limited, further studies are required. Within the Calliphoridae, the Chrysomyinae were recovered as sister taxon to Luciliinae + Calliphorinae. Our analyses indicated that mitogenomic data have the potential for illuminating the phylogenetic relationships in the Oestroidea as well as for the classification of the Calliphoridae.

Characterizing the Complete Mitochondrial Genome of Arma custos and Picromerus lewisi (Hemiptera: Pentatomidae: Asopinae) and Conducting Phylogenetic Analysis

We characterized the mitochondrial genome (mitogenome) and conducted phylogenetic analyses of 48 Hemiptera species by sequencing and analyzing the mitogenome of Arma custos (Fabricius) and Picromerus lewisi (Scott). The complete mitogenomes of the two predators were 16,024 bp and 19,587 bp in length, respectively, and it contained 37 classical genes, including 13 protein-coding genes (PCGs), 2 ribosomal RNA genes (rRNAs), and 22 transfer RNA genes (tRNAs), and a control region. Most PCGs in these predators use ATN as the start codon. This research revealed that the genes of the two natural enemy species have an A + T content of 75.40% and all tRNAs have a typical cloverleaf structure, with the exception of trnS1, which lacks a dihydrouridine arm. This is the first study to compare the mitochondrial genetic structure of two predatory insects; the mitochondrial genetic structure of individual predatory insects has been sequenced in previous studies. Here, phylogenetic analysis on the basis of amino acid and nucleotide sequences of 13 mitochondrial PCGs using Bayesian inference and maximum likelihood methods were conducted to generate similar tree topologies, which suggested that the two predators with close genetic relationships belong to Asopinae subfamily. Furthermore, the monophyly of the Pentatomoidea superfamily is well accepted despite limited taxon and species sampling. Finally, their complete mitogenome provided data to establish a predator-prey food web, which is the foundation of effective pest management. Our results also enhanced the database of natural enemy insects.

The First Eight Mitogenomes of Leaf-Mining Dactylispa Beetles (Coleoptera: Chrysomelidae: Cassidinae) Shed New Light on Subgenus Relationships

The taxonomic classification of Dactylispa, a large genus of leaf-mining beetles, is problematic because it is currently based on morphology alone. Here, the first eight mitochondrial genomes of Dactylispa species, which were used to construct the first molecular phylogenies of this genus, are reported. The lengths of the eight mitogenomes range from 17,189 bp to 20,363 bp. All of the mitochondrial genomes include 13 protein-coding genes (PCGs), 22 transfer RNA genes (tRNAs), 2 ribosomal RNA genes (rRNAs), and 1 A + T-rich region. According to the nonsynonymous/synonymous mutation ratio (Ka/Ks) of all PCGs, the highest and the lowest evolutionary rates were found for atp8 and cox1, respectively, which is a common phenomenon among animals. According to relative synonymous codon usage, UUA(L) has the highest frequency. With two Gonophorini species as the outgroup, mitogenome-based phylogenetic trees of the eight Dactylispa species were constructed using maximum likelihood (ML) and Bayesian inference (BI) methods based on the PCGs, tRNAs, and rRNAs. Two DNA-based phylogenomic inferences and one protein-based phylogenomic inference support the delimitation of the subgenera Dactylispa s. str. and Platypriella as proposed in the system of Chen et al. (1986). However, the subgenus Triplispa is not recovered as monophyletic. The placement of Triplispa species requires further verification and testing with more species. We also found that both adult body shape and host plant relationship might explain the subgeneric relationships among Dactylispa beetles to a certain degree.

Characterization of the complete mitochondrial genomes of six horseflies (Diptera: Tabanidae)

The family Tabanidae (Insecta: Diptera) is one of the economically most important group of haematophagous insects, causing millions of livestock deaths per year. However, current knowledge on the mitochondrial genomes (mitogenomes) from this family is limited. Additional tabanid mitogenomes characterization is of utmost importance for their identification, epidemiologic and phylogenetic studies. We sequenced the mt genomes of six horseflies with an Illumina platform and their phylogenetic relationship was conducted with other infraorder Tabanomorpha members with available mt genome datasets. All six newly sequenced mitogenomes were typical 37-gene circular structures retaining the gene order of Tabanomorpha. The trnQ, trnM and trnA were highly conserved among the six mitogenomes (identity = 100%). The TΨC arm and variable loop regions were relatively more variable compared to the amino acid receptor arm, anticodon arm and DHU arm of the tRNAs. Among 13 protein-coding genes (PCGs) of tabanids mitogenomes, the highest nucleotide diversity was detected in atp8, cox1, cox3, nad6 and cytb (0.1 for each). In addition, atp8 genes exhibited the highest evolutionary rate (ω = 0.24) among 13 PCGs. The interspecies K2P genetic distances among some Tabanus spp. across the mitogenome was greater (0.08) than intergeneric genetic distance between T. amaenus and Atylotus miser (0.07). Phylogenetic analyses revealed non-monophyletic relationships among horseflies of the genus Tabanus. The present study showed mt gene order is highly conserved within Tabanus species. Our mito-phylogenomic analysis supports the paraphyly of the genus Tabanus. The new data provide novel genetic markers for studies of population genetics and systematics of horseflies.

The complete mitochondrial genome of Fannia scalaris (Diptera: Muscidae)

Fannia scalaris (Fabricius, 1794) is closely related to human life in ecological habits, which can lead to health concerns since they feed on various contamination sources. In this study, we first present the mitochondrial genome (mitogenome) of F. scalaris (GenBank No. MT017706). The length of this mitogenome was composed of 15,040 base pairs, including 13 protein-coding genes, two ribosomal RNA, 22 transfer RNA, and an AT-rich region. It consisted of A 39.3%, G 9.1%, C 13.0%, and T 38.6%. The arrangement of the genes was consistent with that of the ancestral metazoan. Furthermore, phylogenetic relationship indicated that F. scalaris was obviously separated from the muscid flies. This study provides useful genetic data in order to further understand the evolutionary relationship of the Muscidae.

Review of Synthesiomyia nudiseta (Diptera: Muscidae) as a useful tool in forensic entomology

Synthesiomyia nudiseta (van der Wulp, 1883) is a synanthropic muscid found in tropical and subtropical zones around the world. The larvae of this species are a secondary agent of myiasis with necrophagous habits and play an important role in forensic entomology, as they are used as an indicator of post-mortem interval. Adults can be considered vectors of etiological agents such as Escherichia coli and Shigella dysenteriae. Due to its ability to adapt to different environmental conditions, its high dispersal capacity (shown by its introduction to Europe), its predatory habits in the last larval stage and the difficulty of identifying it, a very important goal is to update our knowledge about this species. Therefore, the main objective of this paper is to review the identification, geographical distribution and biology of this species in order to provide better support to investigations involving this fly.

The complete mitochondrial genome of Sarcophaga scopariiformis (Diptera: Sarcophagidae)

Sarcophaga scopariiformis (Diptera: Sarcophagidae), a potential vector of pathogens as well as one of the important flesh fly specie in forensic entomology. We have firstly sequenced and assembled the whole mitogenome of S. scopariiformis in this study. The circular mitogenome is 15,325 bp in length, consisting of A (39.3%), G (9.4%), T (36.8%), and C (14.5%). It showed in a typical mitochondrial genome similar to other sarcophagids species, which is composed of 13 protein-coding genes (PCGs), 22 transfer RNA genes (tRNA), 2 ribosomal RNA genes (rRNA), and a non-coding AT-rich region. Moreover, the phylogenetic analysis based on 13 PCGs has been conducted. The topological structure of the phylogenetic tree clearly indicated that S. scopariiformis was more closed to the species of Sarcophaga peregrina in genetic distance, compared to the other sarcophagids species. This study provided a useful data reference for genetic structure and phylogenetic analysis of Sarcophagidae.

The complete mitochondrial genome of Sarcophaga pterygota (Diptera: Sarcophagidae)

Sarcophaga pterygota (Diptera: Sarcophagidae) plays a crucial role in medical and veterinary management. The complete mitochondrial genome (mitogenome) of S. pterygota was first sequenced and annotated. The circle DNA is composed of 13 protein-coding genes (13 PCGs), 2 ribosomal RNA (2 rRNAs), 22 transfer RNA (22 tRNAs) and a AT-rich region. It shows that arrangement of the genes is similar with the classical metazoan. The size of mitogenome is 15,236 bp containing A (40.0%), G (9.3%), T (36.6%), and C (14.1%). Moreover, phylogenetic analysis reveals that the branch of S. pterygota is clustered separately. This study enriches the mitogenome database of flesh flies and represents progress for analyzing of phylogenetic relationships.

The complete mitochondrial genome of Sarcophaga tuberosa (Diptera: Sarcophagidae)

Sarcophaga tuberosa has certain sanitary and epidemiological significance and takes proteins from decaying matter. In this study, we first sequenced and analyzed the complete mitochondrial genome (mitogenome) of S. tuberosa. The length of mitogenome was 15,173 bp, consisting of A (39.5%), G (9.4%), T (37.0%), and C (14.1%), and the order and orientation of genes were identical with that from the mittogenomes of flesh flies previously reported. Phylogenetic analyses showed that S. tuberosa was clustered separately, but which was closed to the species of Sarcophaga portschinskyi. This study provided better support for further understanding of phylogenetic relationships and enriched the mitogenome database of flesh flies.

The complete mitochondrial genome of Sarcophaga brevicornis (Diptera: Sarcophagidae)

Sarcophaga brevicornis (Diptera: Sarcophagidae) was of utmost forensic importance due to their wide distribution, ubiquitous, and synanthropic nature. The complete mitochondrial genome (mitogenome) of S. brevicornis was first sequenced and assembled in this study. The length of circular mitogenome was 15,152 bp, which showed in a typical arthropod genome, including 13 protein-coding genes (13 PCGs), two ribosomal RNA (two rRNA) genes, 22 transfer RNA (22 tRNA) genes, and an AT-rich region. Its nucleotide composition was A 39.0%, C 12.7%, G 10.6%, and T 37.7%. Furthermore, phylogenetic relationships of S. brevicornis and the published sarcophagid species were evaluated based on 13 PCGs. The results indicated that S. brevicornis was clearly separated from the other sarcophagid species, but it was closed to the species of Sarcophaga similis. This study provided a significant database reference for genetic structure and phylogenetic analysis of Sarcophagidae.