Integrative insect taxonomy based on morphology, mitochondrial DNA, and hyperspectral reflectance profiling

A methodological approach to age estimation of the intra-puparial period of the forensically relevant blow fly Calliphora vicina via Fourier transform infrared spectroscopy

Estimating the age of immature blow flies is of great importance for forensic entomology. However, no gold-standard technique for an accurate determination of the intra-puparial age has yet been established. Fourier transform infrared (FTIR) spectroscopy is a method to (bio-)chemically characterise material based on the absorbance of electromagnetic energy by functional groups of molecules. In recent years, it also has become a powerful tool in forensic and life sciences, as it is a fast and cost-effective way to characterise all kinds of material and biological traces. This study is the first to collect developmental reference data on the changes in absorption spectra during the intra-puparial period of the forensically important blow fly Calliphora vicina Robineau-Desvoidy (Diptera: Calliphoridae). Calliphora vicina was reared at constant 20°C and 25°C and specimens were killed every other day throughout their intra-puparial development. In order to investigate which part yields the highest detectable differences in absorption spectra throughout the intra-puparial development, each specimen was divided into two different subsamples: the pupal body and the former cuticle of the third instar, that is, the puparium. Absorption spectra were collected with a FTIR spectrometer coupled to an attenuated total reflection (ATR) unit. Classification accuracies of different wavenumber regions with two machine learning models, i.e., random forests (RF) and support vector machines (SVMs), were tested. The best age predictions for both temperature settings and machine learning models were obtained by using the full spectral range from 3700 to 600 cm-1. While SVMs resulted in better accuracies for C. vicina reared at 20°C, RFs performed almost as good as SVMs for data obtained from 25°C. In terms of sample type, the pupal body gave smoother spectra and usually better classification accuracies than the puparia. This study shows that FTIR spectroscopy is a promising technique in forensic entomology to support the estimation of the minimum post-mortem interval (PMImin), by estimating the age of a given insect specimen.

Intraspecific genetic variation in the lymphatic filariasis vector Mansonia dives (Diptera: Culicidae) in Thailand: Hidden species or genetically divergent populations?

Mansonia dives is recognized as a vector for brugian filariasis in Thailand. A recent study analyzing the cytochrome c oxidase subunit I (COI) gene revealed two distinct clades within the Ma. dives population in Thailand. This study aimed to examine the genetic diversity and structure of Ma. dives using the COI gene and the internal transcribed spacer 2 (ITS2) region to determine the presence of distinct species or genetically divergent populations. We analyzed 60 COI and 60 ITS2 sequences from Ma. dives populations in Narathiwat, Ranong, Tak, and Trat. The results showed a nucleotide diversity of 0.019 and a haplotype diversity of 0.979 for the COI gene, while the ITS2 region displayed a nucleotide diversity of 0.005 and a haplotype diversity of 0.545. Phylogenetic and haplotype network analyses of the COI gene identified two genetic lineages: one confined to Trat and another encompassing the other sites. However, species delimitation methods suggested that these genetic differences were insufficient to classify the lineages as distinct species. In contrast, the ITS2 analysis indicated a uniform genetic pattern across all populations. We conducted neutrality tests and mismatch distribution to examine the demographic history. For the COI gene, Tajima's D was slightly positive and non-significant (0.014), while Fu's Fs was negative (-9.750), indicating a potential expansion phase. Conversely, for the ITS2 region, Tajima's D and Fu's Fs were positive and non-significant, suggesting that the population might be in equilibrium or undergoing contraction. Moreover, the mismatch distribution analysis for the ITS2 region was inconclusive. The apparent discrepancies between these markers indicate the presence of genetically divergent populations, rather than distinct species.

A multiplex direct PCR method for the rapid and accurate discrimination of three species of spider mites (Acari: Tetranychidae) in fruit orchards in Beijing

Spider mites (Acari: Tetranychidae) are polyphagous pests of economic importance in agriculture, among which the two-spotted spider mite Tetranychus urticae Koch has spread widely worldwide as an invasive species, posing a serious threat to fruit tree production in China, including Beijing. The hawthorn spider mite, Amphitetranychus viennensis Zacher, is also a worldwide pest of fruit trees and woody ornamental plants. The cassava mite, Tetranychus truncatus Ehara, is mainly found in Asian countries, including China, Korea and Japan, and mainly affects fruit trees and agricultural crops. These three species of spider mites are widespread and serious fruit tree pests in Beijing. Rapid and accurate identification of spider mites is essential for effective pest and plant quarantine in Beijing orchard fields. The identification of spider mite species is difficult due to their limited morphological characteristics. Although the identification of insect and mite species based on PCR and real-time polymerase chain reaction TaqMan is becoming increasingly common, DNA extraction is difficult, expensive and time-consuming due to the minute size of spider mites. Therefore, the objective of this study was to establish a direct multiplex PCR method for the simultaneous identification of three common species of spider mites in orchards, A. viennensis, T. truncatus and T. urticae, to provide technical support for the differentiation of spider mite species and phytosanitary measures in orchards in Beijing. Based on the mitochondrial cytochrome c oxidase subunit I (COI) of the two-spotted spider mite and the cassava mite and the 18S gene sequence of the hawthorn spider mite as the amplification target, three pairs of specific primers were designed, and the primer concentrations were optimized to establish a direct multiplex PCR system for the rapid and accurate discrimination of the three spider mites without the need for DNA extraction and purification. The method showed a high sensitivity of 0.047 ng for T. truncatus and T. urticae DNA and 0.0002 ng for A. viennensis. This method eliminates the DNA extraction and sequencing procedures of spider mite samples, offers a possibility for rapid monitoring of multiple spider mites in an integrated microarray laboratory system, reducing the time and cost of leaf mite identification and quarantine monitoring in the field.

A comparative study revealed hyperspectral imaging as a potential standardized tool for the analysis of cuticle tanning over insect development

Cereal-feeding beetles are a major risk for cereal crop maintenance. Cereal weevils such as Sitophilus oryzae have symbiotic intracellular bacteria that provide essential aromatic amino acid to the host for the biosynthesis of their cuticle building blocks. Their cuticle is an important protective barrier against biotic and abiotic stresses, providing high resistance from insecticides. Quantitative optical methods specialized in insect cuticle analysis exist, but their scope of use and the repeatability of the results remain limited. Here, we investigated the potential of Hyperspectral Imaging (HSI) as a standardized cuticle analysis tool. Based on HSI, we acquired time series of average reflectance profiles from 400 to 1000 nm from symbiotic (with bacteria) and aposymbiotic (without bacteria) cereal weevils S. oryzae exposed to different nutritional stresses. We assessed the phenotypic changes of weevils under different diets throughout their development and demonstrated the agreement of the results between the HSI method and the classically used Red-Green-Blue analysis. Then, we compared the use of both technologies in laboratory conditions and highlighted the assets of HSI to develop a simple, automated, and standardized analysis tool. This is the first study showing the reliability and feasibility of HSI for a standardized analysis of insect cuticle changes.

Highly Efficient Use of Infrared Spectroscopy (ATR-FTIR) to Identify Aphid Species

Aphids are commonly considered to be serious pests for trees, herbaceous and cultivated plants. Recognition and identification of individual species is very difficult and is based mainly on morphological features. The aims of the study were to suggest the possibility of identifying aphids through the use of Fourier-transform infrared (FTIR) spectroscopy, and to determine which absorption peaks are the most useful to separate aphid species. Using FTIR spectroscopy, based on the chemical composition of the body, we were able to distinguish 12 species of aphid. We have shown that using nine distinct peaks corresponding to the molecular vibrations from carbohydrates, lipids, amides I and II, it is possible to accurately identify aphid species with an efficiency of 98%.

Structural Features and Phylogenetic Implications of 11 New Mitogenomes of Typhlocybinae (Hemiptera: Cicadellidae)

To explore the characteristics of mitogenomes and discuss the phylogenetic relationships and molecular evolution of the six tribes within Typhlocybinae, 11 complete mitogenomes are newly sequenced and comparatively analyzed. In all of these complete mitogenomes, the number and order of the genes are highly conserved in overall organization. The PCGs initiate with ATN/TTG/GTG and terminate with TAA/TAG/T. Almost all tRNAs are folded into the typical clover-leaf secondary structure. The control region is always variable in length and in numbers of multiple tandem repeat units. The atp8 and nad2 exhibits the highest evolution rate among all the PCGs. Phylogenetic analyses based on whole mitogenome sequences, with three different datasets, using both maximum likelihood and Bayesian methods, indicate the monophyly of Typhlocybinae and its inner tribes, respectively, except for Typhlocybini and Zyginellini that are paraphyletic. Finally, we confirm that Erythroneurini is a subtribe of Dikraneurini.

Characterization of Two Complete Mitochondrial Genomes of Ledrinae (Hemiptera: Cicadellidae) and Phylogenetic Analysis

Mitochondrial genomes are widely used for investigations into phylogeny, phylogeography, and population genetics. More than 70 mitogenomes have been sequenced for the diverse hemipteran superfamily Membracoidea, but only one partial and two complete mtgenomes mitochondrial genomes have been sequenced for the included subfamily Ledrinae. Here, the complete mitochondrial genomes (mitogenomes) of two additional Ledrinae species are newly sequenced and comparatively analyzed. Results show both mitogenomes are circular, double-stranded molecules, with lengths of 14,927 bp (Tituria sagittata) and 14,918 bp (Petalocephala chlorophana). The gene order of these two newly sequenced Ledrinae is highly conserved and typical of members of Membracoidea. Similar tandem repeats in the control region were discovered in Ledrinae. Among 13 protein-coding genes (PCGs) of reported Ledrinae mitogenomes, analyses of the sliding window, nucleotide diversity, and nonsynonymous substitution (Ka)/synonymous substitution (Ks) indicate atp8 is a comparatively fast-evolving gene, while cox1 is the slowest. Phylogenetic relationships were also reconstructed for the superfamily Membracoidea based on expanded sampling and gene data from GenBank. This study shows that all subfamilies (sensu lato) are recovered as monophyletic. In agreement with previous studies, these results indicate that leafhoppers (Cicadellidae) are paraphyletic with respect to the two recognized families of treehoppers (Aetalionidae and Membracidae). Relationships within Ledrinae were recovered as (Ledra + (Petalocephala + Tituria)).

A review: application of remote sensing as a promising strategy for insect pests and diseases management

The present review provides a perspective angle on the historical and cutting-edge strategies of remote sensing techniques and its applications, especially for insect pest and plant disease management. Remote sensing depends on measuring, recording, and processing the electromagnetic radiation reflected and emitted from the ground target. Remote sensing applications depend on the spectral behavior of living organisms. Today, remote sensing is used as an effective tool for the detection, forecasting, and management of insect pests and plant diseases on different fruit orchards and crops. The main objectives of these applications were to collate data that help in decision-making for insect pest management and decreasing the environmental pollution of chemical pesticides. Airborne remote sensing has been a promising and useful tool for insect pest management and weed detection. Furthermore, remote sensing using satellite information proved to be a promising tool in forecasting and monitoring the distribution of locust species. It has also been used to help farmers in the early detection of mite infestation in cotton fields using multi-spectral systems, which depend on color changes in canopy semblance over time. Remote sensing can provide fast and accurate forecasting of targeted insect pests and subsequently minimizing pest damage and the management costs.

Phylogeny and revision of the Oriental leafhopper genus Amritodus (Hemiptera: Cicadellidae: Idiocerini)

The phylogeny of the Oriental leafhopper genus Amritodus is reconstructed, for the first time, based on 47 discrete morphological characters and DNA sequence data from one nuclear and two mitochondrial genes. The phylogenetic results show that Amritodus is not monophyletic, and its concept is narrowed here to include four species: Amritodus atkinsoni, Amritodus brevis, Amritodus brevistylus and Amritodus saeedi. The phylogenetic results support establishment of a new genus, Paramritodus gen. nov., with three new species,Paramritodus triangulus sp. nov. (type species), Paramritodus introflexus sp. nov., Paramritodus spatiosus sp. nov. and three species previously included in Amritodus: Paramritodus pistacious comb. nov., Paramritodus flavocapitatus comb. nov. and Paramritodus podocarpus comb. nov. In addition, Amritodus flavoscutatus is transferred from Amritodus to Hyalinocerus as Hyalinocerus flavoscutatus comb. nov. Keys to species of Amritodus and Paramritodus are provided.

DNA barcoding of Deltocephalus Burmeister leafhoppers (Cicadellidae, Deltocephalinae, Deltocephalini) in China

We investigated the feasibility of using the DNA barcode region in identifying Deltocephalus from China. Sequences of the barcode region of the mitochondrial COI gene were obtained for 98 specimens (Deltocephalusvulgaris – 88, Deltocephaluspulicaris – 5, Deltocephalusuncinatus – 5). The average genetic distances among morphological and geographical groups of D.vulgaris ranged from 0.9% to 6.3% and among the three species of Deltocephalus ranged from 16.4% to 21.9% without overlap, which effectively reveals the existence of a “DNA barcoding gap”. It is important to assess the status of these morphological variants and explore the genetic variation among Chinese populations of D.vulgaris because the status of this species has led to taxonomic confusion because specimens representing two distinct morphological variants based on the form of the aedeagus are often encountered at a single locality. Forty-five haplotypes (D.vulgaris – 36, D.pulicaris – 5, D.uncinatus – 4) were defined to perform the phylogenetic analyses; they revealed no distinct lineages corresponding either to the two morphotypes of D.vulgaris or to geographical populations. Thus, there is no evidence that these variants represent genetically distinct species.

Identification of Nilaparvata lugens and Its Two Sibling Species (N. bakeri and N. muiri) by Direct Multiplex PCR

The brown planthopper (BPH), Nilaparvata lugens (Stål) (Hemiptera: Delphacidae), is a destructive rice pest of Asia. Currently, one important monitoring method of BPH is through black light trapping. However, two sibling species of BPH, Nilaparvata bakeri (Muri) and Nilaparvata muiri China, can also be trapped by black light, and these species feed only on gramineous weeds rather than on rice. Therefore, the accurate identification of Nilaparvata species is crucial for N. lugens forecasting and management. The traditional morphological identification method is not feasible for subadults and damaged specimens. Furthermore, this error-prone morphological identification method is time and labor intensive, with the need for expertise and experience. Here, we established a direct multiplex polymerase chain reaction (dmPCR) assay using crude tissue fluid as a template, omitting purified DNA extraction. The crude tissue fluid can be obtained by grinding specimens without any biological reagent but only using distilled water. This dmPCR assay, using three pairs of diagnostic primers, is based on internal transcribed spacers (ITS). Each primer pair amplifies a species-specific fragment of a different size, which were easily and reliably separated in a 2% agarose gel. Furthermore, the dmPCR was verified to be applicable to damaged tissue specimens, such as head, thorax, or abdomen. In conclusion, this dmPCR assay is a novel, time-saving, cost-effective, and easy-to-apply molecular diagnostic method for the identification of the above three sibling species, N. lugens, N. bakeri, and N. muiri.

Hyperspectral imaging to characterize plant-plant communication in response to insect herbivory

BACKGROUND

In studies of plant stress signaling, a major challenge is the lack of non-invasive methods to detect physiological plant responses and to characterize plant-plant communication over time and space.

RESULTS

We acquired time series of phytocompound and hyperspectral imaging data from maize plants from the following treatments: (1) individual non-infested plants, (2) individual plants experimentally subjected to herbivory by green belly stink bug (no visible symptoms of insect herbivory), (3) one plant subjected to insect herbivory and one control plant in a separate pot but inside the same cage, and (4) one plant subjected to insect herbivory and one control plant together in the same pot. Individual phytocompounds (except indole-3acetic acid) or spectral bands were not reliable indicators of neither insect herbivory nor plant-plant communication. However, using a linear discrimination classification method based on combinations of either phytocompounds or spectral bands, we found clear evidence of maize plant responses.

CONCLUSIONS

We have provided initial evidence of how hyperspectral imaging may be considered a powerful non-invasive method to increase our current understanding of both direct plant responses to biotic stressors but also to the multiple ways plant communities are able to communicate. We are unaware of any published studies, in which comprehensive phytocompound data have been shown to correlate with leaf reflectance. In addition, we are unaware of published studies, in which plant-plant communication was studied based on leaf reflectance.

Phylogeny and historical biogeography of leafhopper subfamily Evacanthinae (Hemiptera: Cicadellidae) based on morphological and molecular data

Phylogenetic relationships among major lineages of the Evacanthinae, a highly diverse leafhopper subfamily distributed worldwide, were explored by analysing a dataset of 100 discrete morphological characters and DNA sequence data from five gene regions. Sixty-seven taxa representing all evacanthine tribes and all regional faunas, and fourteen putative outgroup taxa were included. Maximum-likelihood and Bayesian analyses yielded similar tree topologies that were well resolved with strong support for the monophyly of Evacanthinae and its four previously included tribes, but indicated that Draconirvana Dietrich, was incorrectly placed to tribe and that Sophonia Walker, Evacanthus Le Peletier &Serville, Bundera Distant, Paraonukia Ishihara and Onukia Matsumura are not monophyletic. Divergence time analysis suggests that the deepest divergences coincided with breakup of Gondwana but that more recent divergences occurred largely within a single biogeographic realm during the Paleogene, with a few long-distance dispersal events. Biogeographical analyses suggest that Evacanthinae originated in Neotropical region. A new tribe, Pentoffiini trib.n., is established to include Pentoffia Kramer and Evanirvana Hill, the genus Draconirvana Dietrich, placement n. is transferred to Evacanthini from Nirvanini, a key to tribes is also given and illustrations of representative genera are provided.

Insect phylogenetics in the digital age

Insect systematists have long used digital data management tools to facilitate phylogenetic research. Web-based platforms developed over the past several years support creation of comprehensive, openly accessible data repositories and analytical tools that support large-scale collaboration, accelerating efforts to document Earth's biota and reconstruct the Tree of Life. New digital tools have the potential to further enhance insect phylogenetics by providing efficient workflows for capturing and analyzing phylogenetically relevant data. Recent initiatives streamline various steps in phylogenetic studies and provide community access to supercomputing resources. In the near future, automated, web-based systems will enable researchers to complete a phylogenetic study from start to finish using resources linked together within a single portal and incorporate results into a global synthesis.

Remote Sensing and Reflectance Profiling in Entomology

Remote sensing describes the characterization of the status of objects and/or the classification of their identity based on a combination of spectral features extracted from reflectance or transmission profiles of radiometric energy. Remote sensing can be benchtop based, and therefore acquired at a high spatial resolution, or airborne at lower spatial resolution to cover large areas. Despite important challenges, airborne remote sensing technologies will undoubtedly be of major importance in optimized management of agricultural systems in the twenty-first century. Benchtop remote sensing applications are becoming important in insect systematics and in phenomics studies of insect behavior and physiology. This review highlights how remote sensing influences entomological research by enabling scientists to nondestructively monitor how individual insects respond to treatments and ambient conditions. Furthermore, novel remote sensing technologies are creating intriguing interdisciplinary bridges between entomology and disciplines such as informatics and electrical engineering.