DNA barcoding of Sialis sp. (Megaloptera) in Portugal: the missing tool to species identification
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ABSTRACT:
SUBMITTER: Sónia Ferreira
PROVIDER: S-BSST335 | biostudies-other |
REPOSITORIES: biostudies-other
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Project description:In recent years, the number of sequences of diverse species submitted to GenBank has grown explosively and not infrequently the data contain errors. This problem is extensively recognized but not for invalid or incorrectly identified species, sample mixed-up, and contamination. DNA barcoding is a powerful tool for identifying and confirming species and one very important application involves forensics. In this study, we use DNA barcoding to detect erroneous sequences in GenBank by evaluating deep intraspecific and shallow interspecific divergences to discover possible taxonomic problems and other sources of error. We use the mitochondrial DNA gene encoding cytochrome b (Cytb) from turtles to test the utility of barcoding for pinpointing potential errors. This gene is widely used in phylogenetic studies of the speciose group. Intraspecific variation is usually less than 2.0% and in most cases it is less than 1.0%. In comparison, most species differ by more than 10.0% in our dataset. Overlapping intra- and interspecific percentages of variation mainly involve problematic identifications of species and outdated taxonomies. Further, we detect identical problems in Cytb from Insectivora and Chiroptera. Upon applying this strategy to 47,524 mammalian CoxI sequences, we resolve a suite of potentially problematic sequences. Our study reveals that erroneous sequences are not rare in GenBank and that the DNA barcoding can serve to confirm sequencing accuracy and discover problems such as misidentified species, inaccurate taxonomies, contamination, and potential errors in sequencing.
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Project description:The discipline taxonomy (the science of naming and classifying organisms, the original bioinformatics and a basis for all biology) is fundamentally important in ensuring the quality of life of future human generation on the earth; yet over the past few decades, the teaching and research funding in taxonomy have declined because of its classical way of practice which lead the discipline many a times to a subject of opinion, and this ultimately gave birth to several problems and challenges, and therefore the taxonomist became an endangered race in the era of genomics. Now taxonomy suddenly became fashionable again due to revolutionary approaches in taxonomy called DNA barcoding (a novel technology to provide rapid, accurate, and automated species identifications using short orthologous DNA sequences). In DNA barcoding, complete data set can be obtained from a single specimen irrespective to morphological or life stage characters. The core idea of DNA barcoding is based on the fact that the highly conserved stretches of DNA, either coding or non coding regions, vary at very minor degree during the evolution within the species. Sequences suggested to be useful in DNA barcoding include cytoplasmic mitochondrial DNA (e.g. cox1) and chloroplast DNA (e.g. rbcL, trnL-F, matK, ndhF, and atpB rbcL), and nuclear DNA (ITS, and house keeping genes e.g. gapdh). The plant DNA barcoding is now transitioning the epitome of species identification; and thus, ultimately helping in the molecularization of taxonomy, a need of the hour. The 'DNA barcodes' show promise in providing a practical, standardized, species-level identification tool that can be used for biodiversity assessment, life history and ecological studies, forensic analysis, and many more.
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Project description:Species identification using DNA sequences, known as DNA barcoding has been widely used in many applied fields. Current barcoding methods are usually based on a single mitochondrial locus, such as cytochrome c oxidase subunit I (COI). This type of barcoding method does not always work when applied to species separated by short divergence times or that contain introgressed genes from closely related species. Herein we introduce a more effective multi-locus barcoding framework that is based on gene capture and "next-generation" sequencing. We selected 500 independent nuclear markers for ray-finned fishes and designed a three-step pipeline for multilocus DNA barcoding. We applied our method on two exemplar datasets each containing a pair of sister fish species: Siniperca chuatsi vs. Sini. kneri and Sicydium altum vs. Sicy. adelum, where the COI barcoding approach failed. Both of our empirical and simulated results demonstrated that under limited gene flow and enough separation time, we could correctly identify species using multilocus barcoding method. We anticipate that, as the cost of DNA sequencing continues to fall that our multilocus barcoding approach will eclipse existing single-locus DNA barcoding methods as a means to better understand the diversity of the living world.
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Project description:Spiders are mega diverse arthropods and play an important role in the ecosystem. Identification of this group is challenging due to their cryptic behavior, sexual dimorphism, and unavailability of taxonomic keys for juveniles. To overcome these obstacles, DNA barcoding plays a pivotal role in spider identification throughout the globe. This study is the first large scale attempt on DNA barcoding of spiders from India with 101 morphospecies of 72 genera under 21 families, including five endemic species and holotypes of three species. A total of 489 barcodes was generated and analyzed, among them 85 novel barcodes of 22 morphospecies were contributed to the global database. The estimated delimitation threshold of the Indian spiders was 2.6% to 3.7% K2P corrected pairwise distance. The multiple species delimitation methods (BIN, ABGD, GMYC and PTP) revealed a total of 107 molecular operational taxonomic units (MOTUs) for 101 morphospecies. We detected more than one MOTU in 11 morphospecies with discrepancies in genetic distances and tree topologies. Cryptic diversity was detected in Pardosa pusiola, Cyclosa spirifera, and Heteropoda venatoria. The intraspecies distances which were as large as our proposed delimitation threshold were observed in Pardosa sumatrana, Thiania bhamoensis, and Cheiracanthium triviale. Further, shallow genetic distances were detected in Cyrtophora cicatrosa, Hersilia savignyi, Argiope versicolor, Phintella vittata, and Oxyopes birmanicus. Two morphologically distinguished species (Plexippus paykulli and Plexippus petersi) showed intra-individual variation within their DNA barcode data. Additionally, we reinstate the original combination for Linyphia sikkimensis based on both morphology and DNA barcoding. These data show that DNA barcoding is a valuable tool for specimen identification and species discovery of Indian spiders.
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Project description:DNA barcoding with a new cytochrome oxidase c subunit 1 primer set generated a 721 to 724?bp fragment used for the identification of 322 Meloidogyne specimens, including 205 new sequences combined with 117 from GenBank. A maximum likelihood analysis grouped the specimens into 19 well-supported clades and four single-specimen lineages. The "major" tropical apomictic species ( Meloidogyne arenaria , Meloidogyne incognita , Meloidogyne javanica ) were not discriminated by this barcode although some closely related species such as Meloidogyne konaensis were characterized by fixed diagnostic nucleotides. Species that were collected from multiple localities and strongly characterized as discrete lineages or species include Meloidogyne enterolobii , Meloidogyne partityla , Meloidogyne hapla , Meloidogyne graminicola , Meloidogyne naasi , Meloidogyne chitwoodi , and Meloidogyne fallax . Seven unnamed groups illustrate the limitations of DNA barcoding without the benefit of a well-populated reference library. The addition of these DNA sequences to GenBank and the Barcode of Life Database (BOLD) should stimulate and facilitate root-knot nematode identification and provide a first step in new species discovery.
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Project description:DNA barcoding is a molecular method that uses a short standardized DNA sequence as a species identification tool. In this study, the standard 652 base-pair region of the mitochondrial cytochrome oxidase subunit I gene (COI) was sequenced in marine fish specimens captured in China. The average genetic distance was 50-fold higher between species than within species, as Kimura two parameter (K2P) genetic distances averaged 15.742% among congeners and only 0.319% for intraspecific individuals. There are no overlaps of pairwise genetic variations between conspecific and interspecific comparisons apart from the genera Pampus in which the introgressive hybridization was detected. High efficiency of species identification was demonstrated in the present study by DNA barcoding. Due to the incidence of cryptic species, an assumed threshold is suggested to expedite discovering of new species and biodiversity, especially involving biotas of few studies.
| S-EPMC3108176 | biostudies-literature
Project description:BackgroundTaxonomy that utilizes morphological characteristics has been the gold standard method to identify mosquito species. However, morphological identification is challenging when the expertise is limited and external characters are damaged because of improper specimen handling. Therefore, we explored the applicability of mitochondrial cytochrome C oxidase subunit 1 (COI) gene-based DNA barcoding as an alternative tool to identify mosquito species. In the present study, we compared the morphological identification of mosquito specimens with their differentiation based on COI barcode, in order to establish a more reliable identification system for mosquito species found in Singapore.MethodsWe analysed 128 adult mosquito specimens, belonging to 45 species of 13 genera. Phylogenetic trees were constructed for Aedes, Anopheles, Culex and other genera of mosquitoes and the distinctive clustering of different species was compared with their taxonomic identity.ResultsThe COI-based DNA barcoding achieved a 100% success rate in identifying the mosquito species. We also report COI barcode sequences of 16 mosquito species which were not available previously in sequence databases.ConclusionsOur study utilised for the first time DNA barcoding to identify mosquito species in Singapore. COI-based DNA barcoding is a useful tool to complement taxonomy-based identification of mosquito species.
| S-EPMC4282734 | biostudies-literature
Project description:DNA barcoding based on a fragment of the cytochrome c oxidase subunit I (COI) gene in the mitochondrial genome is widely applied in species identification and biodiversity studies. The aim of this study was to establish a comprehensive barcoding reference database of fishes in the Taiwan Strait and evaluate the applicability of using the COI gene for the identification of fish at the species level. A total of 284 mitochondrial COI barcode sequences were obtained from 85 genera, 38 families and 12 orders of fishes. The mean length of the sequences was 655 base pairs. The average Kimura two parameter (K2P) distances within species, genera, families, orders and classes were 0.21%, 6.50%, 23.70% and 25.60%, respectively. The mean interspecific distance was 31-fold higher than the mean intraspecific distance. The K2P neighbor-joining trees based on the sequence generally clustered species in accordance with their taxonomic classifications. High efficiency of species identification was demonstrated in the present study by DNA barcoding, and we conclude that COI sequencing can be used to identify fish species.
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Project description:BackgroundNemerteans of the genus Malacobdella live inside of the mantle cavity of marine bivalves. The genus currently contains only six species, five of which are host-specific and usually found in a single host species, while the sixth species, M. grossa, has a wide host range and has been found in 27 different bivalve species to date. The main challenge of Malacobdella species identification resides in the similarity of the external morphology between species (terminal sucker, gut undulations number, anus position and gonad colouration), and thus, the illustrations provided in the original descriptions do not allow reliable identification. In this article, we analyse the relationships amongthree species of Malacobdella:M.arrokeana,M.japonica andM.grossa,adding new data for the M.grossa and reporting the first for M. japonica, analysing 658 base pairs of the mitochondrial cytochrome c oxidase subunit I gene(COI).Based on these analyses, we present and discuss the potential of DNA barcoding for Malacobdellaspecies identification.ResultsSixty-four DNA barcoding fragments of the mitochondrial COI gene from three different Malacobdella species (M. arrokeana, M. japonica and M. grossa) are analysed (24 of them newly sequenced for this study, along with four outgroup specimens) and used to delineate species. Divergences, measured as uncorrected differences, between the three species were M.arrokeana-M. grossa11.73%,M.arrokeana-M.japonica 10.62%and M.grossa-M. japonica 10.97%. The mean intraspecific divergence within the ingroup species showed a patent gap with respect to the interspecific ones: 0.18% for M.arrokeana,0.13% for M.grossa and0.02% for M.japonica (rangesfrom 0 to 0.91%).ConclusionsWe conclude that there is a clear correspondence between the molecular data and distinguishing morphological characters. Our results thus indicate that some morphological characters are useful for species identification and support the potential of DNA barcoding for species identification in a taxonomic group with subtle morphological external differences.
| S-EPMC6661291 | biostudies-literature
Project description:Two hundred and seven species of fish, mostly Australian marine fish, were sequenced (barcoded) for a 655 bp region of the mitochondrial cytochrome oxidase subunit I gene (cox1). Most species were represented by multiple specimens, and 754 sequences were generated. The GC content of the 143 species of teleosts was higher than the 61 species of sharks and rays (47.1% versus 42.2%), largely due to a higher GC content of codon position 3 in the former (41.1% versus 29.9%). Rays had higher GC than sharks (44.7% versus 41.0%), again largely due to higher GC in the 3rd codon position in the former (36.3% versus 26.8%). Average within-species, genus, family, order and class Kimura two parameter (K2P) distances were 0.39%, 9.93%, 15.46%, 22.18% and 23.27%, respectively. All species could be differentiated by their cox1 sequence, although single individuals of each of two species had haplotypes characteristic of a congener. Although DNA barcoding aims to develop species identification systems, some phylogenetic signal was apparent in the data. In the neighbour-joining tree for all 754 sequences, four major clusters were apparent: chimaerids, rays, sharks and teleosts. Species within genera invariably clustered, and generally so did genera within families. Three taxonomic groups-dogfishes of the genus Squalus, flatheads of the family Platycephalidae, and tunas of the genus Thunnus-were examined more closely. The clades revealed after bootstrapping generally corresponded well with expectations. Individuals from operational taxonomic units designated as Squalus species B through F formed individual clades, supporting morphological evidence for each of these being separate species. We conclude that cox1 sequencing, or 'barcoding', can be used to identify fish species.
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