ABSTRACT
Background: Onion thrips (Thrips tabaci) is a complex of cryptic species with subtle morphological differences and distinct genetic backgrounds; thus, species identification using traditional methods remains challenging. The existence of different haplotypes and genotypes within a species can significantly influence various aspects of its biology, including host preference, reproductive capacity, resistance to pesticides, and vector competence for plant viruses. Understanding the genetic diversity and population structure of cryptic species within T. tabaci will not only aid in the development of more effective control strategies tailored to specific genetic variants but also in monitoring population dynamics, tracking invasive species, and implementing quarantine measures to prevent the spread of economically damaging thrips biotypes. Methods: This study aims to explore intraspecies genetic diversity and molecular evolutionary relationships of the mitochondrial cytochrome oxidase gene subunit I (mtCOI) in T. tabaci populations from India. To capture diversity within the Indian T. tabaci populations, amplicon sequencing was performed for the thrips mtCOI gene from eight diverse localities in India. A total of 48 sequences retrieved for the mtCOI gene from the NCBI Nucleotide database were analysed. Results: Multiple insertions and deletions were detected at various genomic positions across the populations from different localities, with the highest variation observed in the 300-400 genome position range. Molecular diversity analyses identified 30 haplotypes within the population, with certain subpopulations exhibiting higher gene flow. Analysis of single nucleotide polymorphism patterns within the mtCOI gene across diverse Indian locales revealed significant intrapopulation genetic heterogeneity and its potential repercussions on gene functionality. Elevated F statistics (Fst) values in the northern-western subpopulations suggested high genetic variability, particularly evident in haplotype networks originating mainly from the northern region, notably Delhi. While most populations displayed stable and ancient evolutionary histories, thrips populations from northern, western, and north-eastern regions indicated rapid growth.
Subject(s)
Genetic Variation , Phylogeny , Thysanoptera , Thysanoptera/genetics , Animals , India/epidemiology , Genetic Variation/genetics , Onions/genetics , Haplotypes/genetics , Electron Transport Complex IV/genetics , Genetics, PopulationABSTRACT
Rab GTPase is critical for autophagy processes and is implicated in insect immunity against viruses. In this study, we aimed to investigate the role of FoRabs in the autophagic regulation of antiviral defense against tomato spotted wilt orthotospovirus (TSWV) in Frankliniella occidentalis. Transcriptome analysis revealed the downregulation of FoRabs in viruliferous nymph and adults of F. occidentalis in response to TSWV infection. Manipulation of autophagy levels with 3-MA and Rapa treatments resulted in a 5- to 15-fold increase and a 38-64% decrease in viral titers, respectively. Additionally, interference with FoRab10 in nymphs and FoRab29 in adults led to a 20-90% downregulation of autophagy-related genes, a decrease in ATG8-II (an autophagy marker protein), and an increase in the TSWV titers by 1.5- to 2.5-fold and 1.3- to 2.0-fold, respectively. In addition, the leaf disk and the living plant methods revealed increased transmission rates of 20.8-41.6 and 68.3-88.3%, respectively. In conclusion, FoRab10 and FoRab29 play a role in the autophagic regulation of the antiviral defense in F. occidentalis nymphs and adults against TSWV, respectively. These findings offer insights into the intricate immune mechanisms functional in F. occidentalis against TSWV, suggesting potential targeted strategies for F. occidentalis and TSWV management.
Subject(s)
Autophagy , Disease Resistance , Insect Proteins , Plant Diseases , Thysanoptera , Tospovirus , Animals , Tospovirus/physiology , Tospovirus/immunology , Plant Diseases/virology , Plant Diseases/immunology , Plant Diseases/genetics , Thysanoptera/virology , Thysanoptera/immunology , Thysanoptera/genetics , Disease Resistance/genetics , Disease Resistance/immunology , Insect Proteins/genetics , Insect Proteins/immunology , Insect Proteins/metabolism , Solanum lycopersicum/virology , Solanum lycopersicum/immunology , Solanum lycopersicum/genetics , Nymph/immunology , Nymph/growth & development , Nymph/virology , Nymph/genetics , rab GTP-Binding Proteins/genetics , rab GTP-Binding Proteins/immunology , rab GTP-Binding Proteins/metabolismABSTRACT
The western flower thrips Frankliniella occidentalis (Thysanoptera: Thripidae) is a global invasive species that causes increasing damage by direct feeding on crops and transmission of plant viruses. Here, we assemble a previously published scaffold-level genome into a chromosomal level using Hi-C sequencing technology. The assembled genome has a size of 302.58 Mb, with a contig N50 of 1533 bp, scaffold N50 of 19.071 Mb, and BUSCO completeness of 97.8%. All contigs are anchored on 15 chromosomes. A total of 16,312 protein-coding genes are annotated in the genome with a BUSCO completeness of 95.2%. The genome contains 492 non-coding RNA, and 0.41% of interspersed repeats. In conclusion, this high-quality genome provides a convenient and high-quality resource for understanding the ecology, genetics, and evolution of thrips.
Subject(s)
Genome, Insect , Thysanoptera , Thysanoptera/genetics , AnimalsABSTRACT
As the predominant pest of alfalfa, Odontothrips loti Haliday causes great damages over the major alfalfa-growing regions of China. The characteristics of strong mobility and fecundity make them develop rapidly in the field and hard to be controlled. There is a shortage of bioinformation and limited genomic resources available of O. loti for us to develop novel pest management strategies. In this study, we constructed a chromosome-level reference genome assembly of O. loti with a genome size of 346.59 Mb and scaffold N50 length of 18.52 Mb, anchored onto 16 chromosomes and contained 20128 genes, of which 93.59% were functionally annotated. The results of 99.20% complete insecta_odb10 genes in BUSCO analysis, 91.11% short reads mapped to the ref-genome, and the consistent tendency among the thrips in the distribution of gene length reflects the quality of genome. Our study provided the first report of genome for the genus Odontothrips, which offers a genomic resource for further investigations on evolution and molecular biology of O. loti, contributing to pest management.
Subject(s)
Genome, Insect , Thysanoptera , Animals , Thysanoptera/genetics , Chromosomes, Insect/geneticsABSTRACT
Frankliniella occidentalis (Pergande) is a typical omnivorous insect that feeds on host plants, pollens and mite eggs, and poses a threat to crops worldwide. The insulin signalling pathway (ISP) is a typical nutrient-sensitive pathway that participates in the regulation of various functions in insects. Serine/threonine kinases (AKTs) and phosphoinositide-dependent kinases (PDKs) are key components of the ISP. In this study, the FoAKT and FoPDK genes in F. occidentalis were cloned, and the effects of three foods on their expression were determined. The expression of FoAKT and FoPDK in the thrips fed on kidney bean leaves supplemented with pine pollen or mite eggs was higher than in those primarily fed on leaves alone. Meanwhile, the fecundity of thrips fed on leaves supplemented with pine pollen was highest. In addition, RNA interference-mediated knockdown of FoAKT and FoPDK decreased vitellogenin (Vg) content and Vg expression in females, shortened ovariole length, delayed egg development and reduced fecundity and offspring hatching rates. Furthermore, the synthesis of juvenile hormone (JH) was reduced, and the contents of glucose, trehalose, glycogen and trehalase were affected. These results suggest that FoAKT and FoPDK regulate the reproduction of F. occidentalis by regulating Vg and JH production as well as carbohydrate metabolism.
Subject(s)
Insect Proteins , Reproduction , Thysanoptera , Animals , Insect Proteins/metabolism , Insect Proteins/genetics , Female , Thysanoptera/genetics , Thysanoptera/physiology , Pollen , Proto-Oncogene Proteins c-akt/metabolism , Proto-Oncogene Proteins c-akt/genetics , Juvenile Hormones/metabolism , Mites/physiology , FertilityABSTRACT
Thrips are devastating pests for various crops, and they can rasp tender leaves, terminal buds, and flowers, which specifically causing huge economic losses to cotton production. However, there is very little knowledge about the species composition of thrips in mainland China, as well as the genetic structure of the thrips populations, particularly in the cotton-producing regions. In this study, thrips were collected from 40 geographical locations at 8 different provinces which representing majority cotton-producing belts in China, and mitochondrial cytochrome oxidase subunit I sequence was used to identify species composition and evaluate the genetic diversity of collected thrips individuals. Based on experimental results proven that overall, 10 and 8 species of thrips were identified in seedling and flowering stage respectively, which is corresponding dominant species are Thrip tabaci (Lindeman) and Frankliniella intonsa (Trybom). Genetically, 24 haplotypes were identified in 310 T. tabaci individuals from 10 locations, and 263 haplotypes were detected in 1,861 F. intonsa individuals from 40 locations. Hap1 (T. tabaci) is the most widely distributed haplotype among all the T. tabaci samples. Likewise, Hap 2 is the most widely distributed and abundant haplotype among all samples of F. intonsa. The genetic differentiation degrees of T. tabaci between SXYC population and other 9 populations were high, but its gene flow in these 10 regions was relatively low, which might be due to geographical barriers. The Mantel tests showed no correlation between genetic distance and geographic distance of the 2 thrip species. Demographic analysis results showed that both T. tabaci and F. intonsa experienced population expansion in China. Taken together, this study identifies the species composition of thrips in major cotton-producing regions at different growth periods and evaluates effects of geomorphology on the geographical distribution of haplotypes of dominant thrips T. tabaci and F. intonsa.
Subject(s)
Electron Transport Complex IV , Genetic Variation , Gossypium , Thysanoptera , Animals , Thysanoptera/genetics , China , Gossypium/genetics , Electron Transport Complex IV/genetics , HaplotypesABSTRACT
The flower thrips Frankliniella intonsa (Thysanoptera: Thripidae) is a common insect found in flowers of many plants. Sometimes, F. intonsa causes damage to crops through direct feeding and transmission of plant viruses. Here, we assembled a chromosomal level genome of F. intonsa using the Illumina, Oxford Nanopore (ONT), and Hi-C technologies. The assembled genome had a size of 209.09 Mb, with a contig N50 of 997 bp, scaffold N50 of 13.415 Mb, and BUSCO completeness of 92.5%. The assembled contigs were anchored on 15 chromosomes. A set of 14,109 protein-coding genes were annotated in the genome with a BUSCO completeness of 95.0%. The genome contained 491 non-coding RNA and 0.57% of interspersed repeats. This high-quality genome provides a valuable resource for understanding the ecology, genetics, and evolution of F. intonsa, as well as for controlling thrips pests.
Subject(s)
Genome, Insect , Thysanoptera , Animals , Chromosomes , Flowers , Thysanoptera/geneticsABSTRACT
Inbreeding can have detrimental effects on reproductive fitness, but the extent of lineage-specific variation in these effects remains poorly understood. This study investigated the effects of brother and sister inbreeding on reproductive fitness in 2 lineages (L1 and T) of T. tabaci. Inbred females from both lineages exhibited a significant reduction in longevity compared with the control group. The L1 lineage experienced a 27% and 43% decrease in longevity in the F2 and F3 generations, respectively, while the T lineage showed a similar trend with a 30% and 44% decrease. The T lineage consistently displayed slightly longer lifespans than the L1 lineage across all generations. Brother and sister inbreeding also led to a decrease in fecundity rates in both lineages. In the F3 generation, the number of eggs laid decreased by 59% compared with the F2 generation. The T lineage consistently exhibited slightly lower fecundity rates compared with the L1 lineage. Egg hatchability rates declined with subsequent inbreeding, with the F3 generation showing lower rates compared with the F2 generation. However, the T lineage did not exhibit a significant difference in inbreeding depression for egg hatchability rates, while the L1 lineage demonstrated a noticeable decrease. Deformities observed in male L1 lineage resulting from inbreeding were consistent with disruptions in normal developmental processes, affecting various body parts such as legs, antennae, and wings. Continued inbreeding increased susceptibility to inbreeding depression in terms of longevity, fecundity, and egg hatchability.
Subject(s)
Thysanoptera , Female , Male , Animals , Thysanoptera/genetics , Inbreeding , Ovum , Fertility , Genetic FitnessABSTRACT
The structural cuticle proteins (CPs) play important roles in the development and fitness of insects. However, knowledge about CP gene superfamily is limited in virus-transmitting insect vectors, although its importance on transmission of plant virus has been gradually emphasized. In this study, the genome-wide identification of CP superfamily was conducted in western flower thrips Frankliniella occidentalis that is the globally invasive pest and plant virus vector pest. The pest transmits notorious tomato spotted wilt virus (TSWV) around the world, causing large damage to a wide array of plants. One hundred and twenty-eight F. occidentalis CP genes (FoCPs) were annotated in this study and they were classified into 10 distinct families, including 68 CPRs, 16 CPAP1s, 6 CPAP3s, 2 CPCFCs, 10 Tweedles, 4 CPFs, 16 CPLCPs, and 6 CPGs. The comprehensive analysis was performed including phylogenetic relationship, gene location and gene expression profiles during different development stages of F. occidentalis. Transcriptome analysis revealed more than 30% FoCPs were upregulated at least 1.5-fold when F. occidentalis was infected by TSWV, indicating their potential involvement in TSWV interactions. Our study provided an overview of F. occidentalis CP superfamily. The study gave a better understand of CP's role in development and virus transmission, which provided clues for reducing viral damages through silencing CP genes in insect vectors.
Subject(s)
Thysanoptera , Tospovirus , Animals , Insect Vectors/genetics , Insecta , Phylogeny , Thysanoptera/genetics , Tospovirus/geneticsABSTRACT
Orthotospoviruses, a genera of negative-sense ssRNA viruses transmitted by thrips, have gained significant attention in recent years due to their detrimental impact on diverse crops, causing substantial economic losses and posing threats to food security. Orthotospoviruses are characterised by a wide range of symptoms in plants, including chlorotic/necrotic spots, vein banding, and fruit deformation. Seven species, including four definite and three tentative species in the genus Orthotospovirus, have so far been documented on the crops of the Indian subcontinent. Management of Orthotospoviruses under field conditions is challenging since they have a wide host range, adaptation to versatile environmental conditions, a lack of promising resistance sources, and the ubiquitous nature of thrips and their transmission through a propagative manner. Our present review elucidates the significance, molecular biology and evolutionary relationship of Orthotospoviruses; vector population; and possible management strategies for Orthotospoviruses and their vectors in the scenario of the Indian subcontinent.
Subject(s)
Thysanoptera , Tospovirus , Animals , Plant Diseases , Tospovirus/genetics , Thysanoptera/genetics , Crops, Agricultural , AgricultureABSTRACT
The mitochondrial gene order in Thysanoptera is notably distinct and highly rearranged, with each species exhibiting its own unique arrangement. To elucidate the relationship between gene rearrangements and phylogeny, the complete mitochondrial genome (mitogenome) of the wheat pest, Aptinothrips stylifer, was sequenced and assembled, spanning a total length of 16,033 bp. Compared with the ancestral arthropod mitogenome, significant rearrangement differences were evident in A. stylifer, whereas the gene order between A. stylifer and Anaphothrips obscurus was similar. Phylogenetic trees were reconstructed based on all 13 protein-coding gene sequences using Bayesian inference and maximum-likelihood methods, both yielding similar topological structures. Notably, A. stylifer was robustly clustered with A. obscurus, affirming its classification within Anaphothrips genus group. This exemplifies the potential correlation between gene rearrangements and phylogeny in the Thripidae family. Additionally, the mitogenome of A. stylifer exhibited several atypical features, including: (1) Three putative control regions (CRs) in close proximity, with CR2 and CR3 displaying partial similarity, and CR1 differing in base composition; (2) Two transfer RNAs (tRNAs), trnS1 and trnV, lacking the DHU arm; (3) Two ribosomal RNA (rRNA) genes inverted and positioned distant from each other; (4) Negative AT and GC skew (AT skew = -0.001, GC skew = -0.077); (5) One transposition (nad6), one inverse transposition (trnQ), four inversions (trnF, trnH, trnC, and gene block nad1-trnL1-rrnL-trnV-rrnS), and four tandem duplication random loss events; and (6) Two protein-coding genes, nad2 and atp8, terminated with an incomplete stop codon "T".
Subject(s)
Genome, Mitochondrial , Thysanoptera , Animals , Phylogeny , Thysanoptera/genetics , Triticum/genetics , Bayes TheoremABSTRACT
A new species of Scirtothrips is described from India, S. donumdei, collected on leaves of Senegalia pennata (Fabaceae). Partial mitochondrial cytochrome c oxidase subunit 1 (mtCOI) gene sequence of the species was sequenced and the annotated sequence was submitted to NCBI GenBank.
Subject(s)
Fabaceae , Thysanoptera , Animals , Thysanoptera/genetics , India , Plant Leaves , MitochondriaABSTRACT
The mitochondrial genome (mitogenome) of thrips is characterized by the presence of control region (CR) duplication. However, the evolution pattern of duplicated CRs in thrips is still unclear. In this study, the multiple independent origins of duplicated CR indicated that the CR duplication was not an ancestral state for Thysanoptera. The macroevolutionary pattern suggested that the earliest CR duplication event occurred in the middle Cretaceous (94.85 Ma) coincided with rearrangement events forming the ancestors of Aeolothripidae, but much later than that forming the ancestors of the suborder Terebrantia. The mitogenome with duplicated CRs showed a higher rate of gene rearrangement. The sequence similarity of the CR copies and divergence time were negatively correlated, indicating age-related deterioration of mitochondrial function. No significant differences were found in the mitochondrial DNA, the P123 and P4FD between the single and multiple-CR charactered mitogenomes, which suggested that the duplicated CRs may not affect the replication process in thrip mitogenome. The mitogenomes with duplicated CRs (mean: 0.0088 subs/s/my) show a significantly increased evolutionary rate than that with a single one (mean: 0.0058 subs/s/my). However, it seems that this higher evolutionary rate did not have adaptive mechanisms in Terebrantia. We speculated that the duplicated CRs may cause a more intense production of energy by mitochondria, and an accelerated mutation and substitution rate is expected in such mitogenomes. Our study provided new insights into the presence of CR duplications and their evolution in the mitogenomes of thrips.
Subject(s)
Thysanoptera , Animals , Thysanoptera/genetics , Evolution, Molecular , Phylogeny , Mitochondria/genetics , Gene Rearrangement , DNA, Mitochondrial/geneticsABSTRACT
Uridine diphosphate glucosyltransferases (UGTs) play crucial roles in the insect detoxification system and are associated with pesticide resistance. Our previous transcriptomic analysis of spinosad-susceptible (Ivf03) and resistant (NIL-R) Frankliniella occidentalis revealed numerous upregulated UGT genes in the NIL-R strain, suggesting their potential contribution to spinosad resistance. To investigate this hypothesis, here we conducted UGT activity assays and spinosad induction experiments, employing RNA interference (RNAi) techniques for gene function validation. We found significantly elevated UGT activity in the NIL-R strain compared to Ivf03, with 5-nitrouracil showing a substantial synergistic effect on the resistant strain. Eighteen UGT genes were identified in F. occidentalis, with gene expansion and duplication observed within families UGT466, 467, and 468. Ten out of the eighteen UGTs exhibited higher expression levels in NIL-R, specifically FoUGT466B1, FoUGT468A3, and FoUGT468A4 consistently being upregulated across nymphs, males, and females. RNAi-based functional validation targeting these three UGT genes led to increased susceptibility to spinosad in a life stage-, sex-, and dose-dependent manner. These results indicate that UGTs are indeed involved in spinosad resistance in F. occidentalis, and the effects are dependent on life stage, sex, and dose. Therefore, sustainable control for F. occidentalis resistance should always consider these differential responses.
Subject(s)
Insecticides , Macrolides , Thysanoptera , Humans , Animals , Male , Female , Thysanoptera/genetics , Thysanoptera/metabolism , Insecticides/toxicity , Insecticides/metabolism , Insecticide Resistance/genetics , Flowers , Drug CombinationsABSTRACT
As an economically important insect pest, the flower thrips Frankliniella intonsa (Trybom) causes great damage to host plants by directly feeding and indirectly transmitting various pathogenic viruses. The lack of a well-assembled genomic resource has hindered our understanding of the genetic basis and evolution of F. intonsa. In this study, we used Oxford Nanopore Technology (ONT) long reads and High-through chromosome conformation capture (Hi-C) linked reads to construct a high-quality reference genome assembly of F. intonsa, with a total size of 225.5 Mb and a contig N50 of 3.37 Mb. By performing the Hi-C analysis, we anchored 91.68% of the contigs into 15 pseudochromosomes. Genomic annotation uncovered 17,581 protein-coding genes and identified 20.09% of the sequences as repeat elements. BUSCO analysis estimated over 98% of genome completeness. Our study is at the first time to report the chromosome-scale genome for the species of the genus Frankliniella. It provides a valuable genomic resource for further biological research and pest management of the thrips.
Subject(s)
Genome, Insect , Thysanoptera , Animals , Chromosomes , Flowers , Genomics , Molecular Sequence Annotation , Phylogeny , Thysanoptera/geneticsABSTRACT
BACKGROUND: Invasive black flower thrips Thrips parvispinus (Karny) has recently emerged as a significant threat to Indian chilli production. Identifying T. parvispinus became difficult due to the complex presence of thrips species in Indian chilli and allied ecosystems. Pest management success depends on assessing invasive pests genetic populations and their distribution in newly habituated areas. METHODS AND RESULTS: The current study investigated the genetic diversity and phylogeographic structure of T. parvispinus across major chilli-growing zones representing different agro-climatic conditions in Tamil Nadu. The species-specific chaetotaxy characteristics of T. parvispinus and molecular analysis of the mtCOI gene were used to confirm that the species T. parvispinus has expanded rapidly in three regions (North Western, Western and Cauvery delta), sparsely in one (Southern) and absent from two (hilly and high rainfall). Fifteen allied crops in chilli/capsicum growing tracts served as host plants for T. parvispinus. A shrub species, namely Littleleaf boxwood, Buxus microphylla Siebold & Zucc., is described as a host plant for the first time. On capsicum and chilli, T. parvispinus and Scirtothrips dorsalis coexisted. Thrips palmi, T. tabaci, Frankliniella schultzei, and Microcephalothrips abdominalis co-occurring alongside T. parvispinus on allied crops. CONCLUSION: Molecular characterization and haplotype identification help define the genetic composition of T. parvispinus and serve as a foundation for efficient monitoring and creation of Integrated Pest Management (IPM) strategies. As a result, the genetic data presented in this work strongly argues that T. parvispinus as a population is resolving itself towards a fixed state through natural selection that spans its native range globally along with low genetic diversity [Hd: 0.771].
Subject(s)
Thysanoptera , Animals , Thysanoptera/genetics , Ecosystem , India , Crops, Agricultural , VegetablesABSTRACT
Insect mitochondrial genomes (mitogenome) generally present a typical gene order, which is considered as the ancestral arrangement. All sequenced mitogenomes in the Thysanoptera display high levels of gene rearrangement. Due to limited number of thrips mitogenomes sequenced, how gene rearrangement may be shaped by evolution remain unclear. Here, we analyzed 33 thrips mitogenomes, including 14 newly sequenced. These mitogenomes were diverse in organization, nucleotides substitution and gene arrangements. We found 28 highly rearranged gene orders with the breakpoints of gene rearrangements from 25 to 33. Reconstruction of the ancestors mitochondrial gene arrangements states indicated that Tubulifera have more complex pathways than Terebrantia in the gene order evolution. Molecular calibration estimated that divergence of two suborders occurred in the middle Triassic while the radiation of thrips was associated with the arose and flourish of angiosperm. Our evolutionary hypothesis testing suggests that relaxation of selection pressure enabled the early phase of Thysanoptera evolution, followed by a stronger selective pressure fixed diversification. Our analyses found gene inversion increases the nonsynonymous substitution rates and provide an evolutionary hypothesis driving the diverse gene orders.
Subject(s)
Genome, Mitochondrial , Thysanoptera , Animals , Thysanoptera/genetics , Genome, Mitochondrial/genetics , Phylogeny , Insecta/genetics , Gene Rearrangement , Gene Order , Evolution, MolecularABSTRACT
Thysanoptera, commonly known as thrips, are diverse tiny insects whose earliest fossil record dates back to the Triassic period. Since there are few studies on the divergence time of taxa under Thysanoptera, this study used 13 mitochondrial coding protein genes to reconstruct the phylogenetic tree with divergence time of 26 species of this order and show a reliable phylogenetic relationship of thrips species. The time tree of this study shows that most extant thrips diverged in the early Tertiary period, while the fossil records also support that most extinct thrips appeared in this period. This study expands our understanding of the evolution of thrips and provides a feasible way of using multiple mitochondrial genes to establish robust phylogenetic relationships and explore divergence time between species.
Subject(s)
Thysanoptera , Animals , Thysanoptera/genetics , Phylogeny , Extinction, Psychological , Fossils , Genes, Mitochondrial , Mitochondrial ProteinsABSTRACT
DNA Barcoding is an important tool for disciplines such as taxonomy, phylogenetics and phylogeography, with Barcode of Life Data System (BOLD) being the largest database of partial cytochrome c oxidase subunit I (COI) sequences. We provide the first extensive revision of the information available in this database for the insect order Thysanoptera, to assess: how many COI sequences are available; how representative these sequences are for the order; and the current potential of BOLD as a reference library for specimen identification and species delimitation. The COI database at BOLD currently represents only about 5% of the over 6400 valid thrips species, with a heavy bias towards a few species of economic importance. Clear Barcode gaps were observed for 24 out of 33 genera evaluated, but many outliers were also observed. We suggest that the COI sequences available in BOLD as a reference would not allow for accurate identifications in about 30% of Thysanoptera species in this database, which rises to 40% of taxa within Thripidae, the most sampled family within the order. Thus, we call for caution and a critical evaluation in using BOLD as a reference library for thrips Barcodes, and future efforts should focus on improving the data quality of this database.
Subject(s)
Thysanoptera , Animals , Thysanoptera/genetics , DNA Barcoding, Taxonomic , Insecta/genetics , Phylogeny , PhylogeographyABSTRACT
Thrips are a serious pest in many crops. In onion cultivation, Thrips tabaci is the most important, but not the only thrips species causing damage. We investigated which thrips species affects onion and related species worldwide, how much genetic variation there is within T. tabaci populations, and how this evolves. Furthermore, we determined the reproductive mode and the correlation between the genetic and geographic distances. Thrips samples from infested onions or related species were obtained from 14 different locations worldwide. Species and haplotypes were determined through DNA barcoding with the mitochondrial Cytochrome Oxidase subunit I (COI) gene. Thrips tabaci was the most commonly observed species, but Scirtothrips dorsalis, Thrips palmi, Frankliniella intonsa, Frankliniella occidentalis and Frankliniella tenuicornis were also found, especially at the beginning of the growing seasons and depending on the location. The Nei's genetic distance within T. tabaci was less than 5% and the haplotypes were clustered into two phylogenetic groups, each linked to a specific mode of reproduction, thelytokous or arrhenotokous. Thelytokous thrips were more common and more widely distributed than arrhenotokous thrips. A high percentage of heteroplasmy was detected in the arrhenotokous group. Heteroplasmic thrips were only found in populations where thelytokous and arrhenotokous were present in sympatry. Some T. tabaci haplotypes were present in high frequency at several sampled locations. No correlation was found between the genetic and geographic distances, which points to anthropic activities spreading thrips haplotypes throughout the world.