Estimating diversity of Indo-Pacific coral reef stomatopods through DNA barcoding of stomatopod larvae

From DNA barcodes to ecology: Meta-analysis of central European beetles reveal link with species ecology but also to data pattern and gaps

DNA barcoding has been used worldwide to identify biological specimens and to delimit species. It represents a cost-effective, fast, and efficient way to assess biodiversity with help of the public Barcode of Life Database (BOLD) accounting for more than 236,000 animal species and more than 10 million barcode sequences. Here, we performed a meta-analysis of available barcode data of central European Coleoptera to detect intraspecific genetic patterns among ecological groups in relation to geographic distance with the aim to investigate a possible link between infraspecific variation and species ecology. We collected information regarding feeding style, body size, as well as habitat and biotope preferences. Mantel tests and two variants of Procrustes analysis, both involving the Principal Coordinates Neighborhood Matrices (PCNM) approach, were applied on genetic and geographic distance matrices. However, significance levels were too low to further use the outcome for further trait investigation: these were in mean for all ecological guilds only 7.5, 9.4, or 15.6% for PCNM + PCA, NMDS + PCA, and Mantel test, respectively, or at best 28% for a single guild. Our study confirmed that certain ecological traits were associated with higher species diversity and foster stronger genetic differentiation. Results suggest that increased numbers of species, sampling localities, and specimens for a chosen area of interest may give new insights to explore barcode data and species ecology for the scope of conservation on a larger scale. We performed a meta-analysis of available barcode data of central European beetles to detect intraspecific genetic patterns among ecological groups in relation to geographic distance, regarding feeding style, body size, as well as habitat and biotope preferences. Our study confirmed that certain ecological traits were associated with higher species diversity and foster stronger genetic differentiation. However, significance levels were too low to further use the outcome for further trait investigation.

Multiple species delimitation approaches with COI barcodes poorly fit each other and morphospecies – An integrative taxonomy case of Sri Lankan Sericini chafers (Coleoptera: Scarabaeidae)

DNA taxonomy including barcoding and metabarcoding is widely used to explore the diversity in biodiversity hotspots. In most of these hotspot areas, chafers are represented by a multitude of species, which are well defined by the complex shape of male genitalia. Here, we explore how well COI barcode data reflect morphological species entities and thus their usability for accelerated species inventorization. We conducted dedicated field surveys in Sri Lanka to collect the species‐rich and highly endemic Sericini chafers (Coleoptera: Scarabaeidae). Congruence among results of a series of protocols for de novo species delimitation and with morphology‐based species identifications was investigated. Different delimitation methods, such as the Poisson tree processes (PTP) model, Statistical Parsimony Analysis (TCS), Automatic Barcode Gap Discovery (ABGD), Assemble Species by Automatic Partitioning (ASAP), and Barcode Index Number (BIN) assignments, resulted in different numbers of molecular operational taxonomic units (MOTUs). All methods showed both over‐splitting and lumping of morphologically identified species. Only 18 of the observed 45 morphospecies perfectly matched MOTUs from all methods. The congruence of delimitation between MOTUs and morphospecies expressed by the match ratio was low, ranging from 0.57 to 0.67. TCS and multirate PTP (mPTP) showed the highest match ratio, while (BIN) assignment resulted in the lowest match ratio and most splitting events. mPTP lumped more species than any other method. Principal coordinate analysis (PCoA) on a match ratio‐based distance matrix revealed incongruent outcomes of multiple DNA delimitation methods, although applied to the same data. Our results confirm that COI barcode data alone are unlikely to correctly delimit all species, in particular, when using only a single delimitation approach. We encourage the integration of various approaches and data, particularly morphology, to validate species boundaries.

Sampling multiple life stages significantly increases estimates of marine biodiversity

Biodiversity assessments are critical for setting conservation priorities, understanding ecosystem function and establishing a baseline to monitor change. Surveys of marine biodiversity that rely almost entirely on sampling adult organisms underestimate diversity because they tend to be limited to habitat types and individuals that can be easily surveyed. Many marine animals have planktonic larvae that can be sampled from the water column at shallow depths. This life stage often is overlooked in surveys but can be used to relatively rapidly document diversity, especially for the many species that are rare or live cryptically as adults. Using DNA barcode data from samples of nemertean worms collected in three biogeographical regions—Northeastern Pacific, the Caribbean Sea and Eastern Tropical Pacific—we found that most species were collected as either benthic adults or planktonic larvae but seldom in both stages. Randomization tests show that this deficit of operational taxonomic units collected as both adults and larvae is extremely unlikely if larvae and adults were drawn from the same pool of species. This effect persists even in well-studied faunas. These results suggest that sampling planktonic larvae offers access to a different subset of species and thus significantly increases estimates of biodiversity compared to sampling adults alone. Spanish abstract is available in the electronic supplementary material.

Improving metabarcoding taxonomic assignment: A case study of fishes in a large marine ecosystem

DNA metabarcoding is an important tool for molecular ecology. However, its effectiveness hinges on the quality of reference sequence databases and classification parameters employed. Here we evaluate the performance of MiFish 12S taxonomic assignments using a case study of California Current Large Marine Ecosystem fishes to determine best practices for metabarcoding. Specifically, we use a taxonomy cross-validation by identity framework to compare classification performance between a global database comprised of all available sequences and a curated database that only includes sequences of fishes from the California Current Large Marine Ecosystem. We demonstrate that the regional database provides higher assignment accuracy than the comprehensive global database. We also document a tradeoff between accuracy and misclassification across a range of taxonomic cutoff scores, highlighting the importance of parameter selection for taxonomic classification. Furthermore, we compared assignment accuracy with and without the inclusion of additionally generated reference sequences. To this end, we sequenced tissue from 597 species using the MiFish 12S primers, adding 252 species to GenBank's existing 550 California Current Large Marine Ecosystem fish sequences. We then compared species and reads identified from seawater environmental DNA samples using global databases with and without our generated references, and the regional database. The addition of new references allowed for the identification of 16 additional native taxa representing 17.0% of total reads from eDNA samples, including species with vast ecological and economic value. Together these results demonstrate the importance of comprehensive and curated reference databases for effective metabarcoding and the need for locus-specific validation efforts.

The development of species-specific AFLP-derived SCAR and SSCP markers to identify mantis shrimp species

Mantis shrimp has become commercially valuable in many countries, while the commercially aquaculture still unsuccessful. The stable supply of the species-specific markers for precise identification can play a key role of foods authentication as well as restoring/enhancing mantis shrimp stocks in future. The aim of this research was to identify species-specific markers for Squillid and Harpiosquillid mantis shrimp taxa using Amplified fragment length polymorphism-Single strand conformation polymorphism (AFLP-SSCP) approaches. Selective amplification would be substituted as a total of 40 primer combinations was performed using either three-base (i.e., EcoRI+3 and MseI+3 in 20 primer combinations) or two-base (i.e., EcoRI+2 and MseI+2 in 20 primer combinations) selective primers. These had been size-fractionated via 6% denaturing polyacrylamide gel electrophoresis, ten AFLP fragments exhibiting species or genus-specific characteristics were cloned, sequenced, and GenBank interrogated. A primer pair was designed and their specificity was tested versus the genomic DNA of various species. Results show that the primer E₊₂-13/M₊₂-13Hr₁₅₈ generated PCR products for just H. harpax, while E₊₃-14/M₊₃-2HhHr₁₅₁ and E₊₂-13/M₊₂-13Hh₁₅₀ generated PCR products for both H. harpax and H. raphidea and not others (i.e., M. nepa, O. oratoria, and E. woodmasoni). SSCP was then applied in order to differentiate between H. harpax and H. raphidea. These SSCP results indicate that species can be differentiated based on polymorphic fragment nucleotides. Indeed, primers E₊₂-13/M₊₂-13Hr₁₅₈, E₊₃-14/M₊₃-2HhHr_151, and E₊₂-13/M₊₂-13Hh₁₅₀ were all successfully confirmed as present in processed mantis shrimp samples (i.e., saline-preserved and heat-dried). These results provide new species-specific markers for mantis shrimp identification.

Using larval barcoding to estimate stomatopod species richness at Lizard Island, Australia for conservation monitoring

Stomatopods (Crustacea, Stomatopoda) are well studied for their aggressive behavior and unique visual system as well as their commercial importance in Asian and European countries. Like many crustaceans, stomatopods undergo indirect development, passing though several larval stages before reaching maturity. Adult stomatopods can be difficult to catch due to their inaccessible habitats and cryptic coloration. By sampling larvae from the planktonic community, less effort is required to obtain accurate measures of species richness within a region. Stomatopod larvae were collected between 2006 and 2015 from the waters around the Lizard Island reef platform in Eastern Australia. Cytochrome oxidase I (COI) mitochondrial DNA sequences were generated from each larval sample and compared to a database of COI sequences tied to adult specimens. Of the 20 species collected from Lizard Island as adults which have COI data available, 18 species were identified from larval sampling. One additional species identified from larval samples, Busquilla plantei, was previously unknown from Lizard Island. Nine larval OTUs were found not to match any published adult sequences. Sampling larval stomatopod populations provides a comparable picture of the adult population to benthic sampling methods and may include species richness beyond what is measurable by sampling adult populations.

Genomic signatures of host-associated divergence and adaptation in a coral-eating snail, Coralliophila violacea (Kiener, 1836)

The fluid nature of the ocean, combined with planktonic dispersal of marine larvae, lowers physical barriers to gene flow. However, divergence can still occur despite gene flow if strong selection acts on populations occupying different ecological niches. Here, we examined the population genomics of an ectoparasitic snail, Coralliophila violacea (Kiener 1836), that specializes on Porites corals in the Indo-Pacific. Previous genetic analyses revealed two sympatric lineages associated with different coral hosts. In this study, we examined the mechanisms promoting and maintaining the snails' adaptation to their coral hosts. Genome-wide single nucleotide polymorphism (SNP) data from type II restriction site-associated DNA (2b-RAD) sequencing revealed two differentiated clusters of C. violacea that were largely concordant with coral host, consistent with previous genetic results. However, the presence of some admixed genotypes indicates gene flow from one lineage to the other. Combined, these results suggest that differentiation between host-associated lineages of C. violacea is occurring in the face of ongoing gene flow, requiring strong selection. Indeed, 2.7% of all SNP loci were outlier loci (73/2,718), indicative of divergence with gene flow, driven by adaptation of each C. violacea lineage to their specific coral hosts.

Cryptic ecological and geographic diversification in coral-associated nudibranchs

Coral reefs are among the most biologically diverse ecosystems of the world, yet little is known about the processes creating and maintaining their diversity. Ecologically, corallivory in nudibranchs resembles phytophagy in insects- a process that for decades has served as a model for ecological speciation via host shifting. This study uses extensive field collections, DNA sequencing, and phylogenetic analyses to reconstruct the evolutionary history of coral-associated nudibranchs and assess the relative roles that host shifting and geography may have played in their diversification. We find that the number of species is three times higher than the number previously known to science, with evidence for both allopatric and ecological divergence through host shifting and host specialization. Results contribute to growing support for the importance of ecological diversification in marine environments and provide evidence for new species in the genus Tenellia.

DNA barcoding of flowering plants in Sumatra, Indonesia

The rapid conversion of Southeast Asian lowland rainforests into monocultures calls for the development of rapid methods for species identification to support ecological research and sustainable land-use management. Here, we investigated the utilization of DNA barcodes for identifying flowering plants from Sumatra, Indonesia. A total of 1,207 matK barcodes (441 species) and 2,376 rbcL barcodes (750 species) were successfully generated. The barcode effectiveness is assessed using four approaches: (a) comparison between morphological and molecular identification results, (b) best-close match analysis with TaxonDNA, (c) barcoding gap analysis, and (d) formation of monophyletic groups. Results show that rbcL has a much higher level of sequence recoverability than matK (95% and 66%). The comparison between morphological and molecular identifications revealed that matK and rbcL worked best assigning a plant specimen to the genus level. Estimates of identification success using best-close match analysis showed that >70% of the investigated species were correctly identified when using single barcode. The use of two-loci barcodes was able to increase the identification success up to 80%. The barcoding gap analysis revealed that neither matK nor rbcL succeeded to create a clear gap between the intraspecific and interspecific divergences. However, these two barcodes were able to discriminate at least 70% of the species from each other. Fifteen genera and twenty-one species were found to be nonmonophyletic with both markers. The two-loci barcodes were sufficient to reconstruct evolutionary relationships among the plant taxa in the study area that are congruent with the broadly accepted APG III phylogeny.

Molecular identification and phylogenetic relationship of flying fishes of Tamil Nadu coast for fishery management purposes

The partial sequences of cytochrome c oxidase subunit I (COI) mitochondrial gene were analysed for developing species specific molecular signatures and phylogenetic relationship among the commercially important flying fishes (Cheilopogon cyanopterus, Cheilopogon furcatus and Hirundichthys coromandelensis) distributed in Tamil Nadu coast. Accurate identification of these species is important for fishery management as its morphological characters are very similar. Since the morphological features are very similar, accurate identification using molecular tools is essential for sustainable utilization and management of these species across their distributional range. The estimated transition/transversion bias (R) is 3.45. The average nucleotide sequences calculated were A = 30.00%, T/U = 26.40%, C = 17.00% and G = 26.60%. Using COI data analysis, the intraspecies genetic distance ranged from 0.00 to 0.05, while it varied from 0.06 to 0.08 for interspecies. Partial sequences of the genes provided sufficient phylogenetic information to distinguish the three flying fishes indicating the usefulness of mtDNA-based approach in species identification.

Planktotrophic Brachiopod Larvae from the Pacific and Caribbean of Panama

Lingulids and discinids are the only brachiopods that exhibit life histories that include a feeding planktonic stage usually referred to as a “larva”. We collected planktotrophic brachiopod larvae from the Pacific and Caribbean coasts of Panama and took a DNA barcoding approach with mitochondrial cytochrome c oxidase subunit I (COI), mitochondrial ribosomal 16S, and nuclear ribosomal 18S genes to identify those larvae and to estimate their diversity in the region. We observed specimens from both coasts with distinct morphologies typical of lingulid and discinid larvae. COI and 16S were sequenced successfully for the lingulid larvae but failed consistently for all discinid larvae. 18S was sequenced successfully for larvae from both families. Sequence data from each gene revealed one lingulid operational taxonomic unit (OTU) from Bocas del Toro on the Caribbean coast, and one lingulid OTU from the Bay of Panama on the Pacific coast. These OTUs differed by >20% for COI, >10% for 16S and ~0.5% for 18S. Both OTUs clustered with GenBank sequences of Glottidia species, the only genus of lingulids in the Americas, but were distinct from G. pyramidata the only species reported for the Caribbean. Analysis of 18S sequence data for discinid larvae recovered 2 OTUs, one exclusively from the Pacific and one with a mixture of Pacific and Caribbean larvae. The 18S marker does not provide enough resolution to distinguish between species, and comparisons with GenBank sequences suggest that one OTU includes Pelagodiscus species, while the other may include Discradisca species. When compared with other marine invertebrates, our surveys of brachiopod larvae through DNA barcoding show relatively low levels of diversity for Panama.

DNA barcoding of Cloridopsis immaculata: genetic distance and phylogeny of stomatopods

The changes of coastal topography might have genetically altered the extant species diversity in Chilika Lake. The genetic assessment of stomatopods has never been attempted from this ecosystem. The study generate the first genetic information (mtCOI) of Cloridopsis immaculata. DNA sequences of C. immaculata shows 12.9% genetic divergence with Harpiosquilla harpax and clade as sister species in NJ tree. Alima, Harpiosquilla, and Oratosquilla shows high congeneric/conspecific genetic divergence (20.9%, 15.7%, and 7.2%) and cladded separately in the phylogeny; correlate to their diverse populations. We recommend more extensive survey of stomatopods and generation of molecular data to resolve the taxonomic uncertainty.

DNA barcoding post-larvae can improve the knowledge about fish biodiversity: an example from La Reunion, SW Indian Ocean

The aim of this study was to demonstrate that fish larvae identified using their COI sequences offer a unique opportunity for improving the knowledge of local fish richness. Fish larvae were sampled at the end of their pelagic phase using light-traps set off the West Coast of La Reunion Island, southwestern Indian Ocean, once per month from October 2014 to March 2015. Among the 5174 larvae caught, 214 morphologically different specimens were selected, 196 successfully barcoded, giving a total of 101 different Barcode Index Numbers (BINs). Among these BINs, 55 had never been recorded in La Reunion exclusive economic zone (EEZ), and 13 were new for the BOLD database. Even if the sampling effort for collecting fish post-larvae during this study was relatively low, it allowed adding at least nine new species to an updated checklist of fishes of La Reunion EEZ.

Cryptic diversity in the Japanese mantis shrimp Oratosquilla oratoria (Crustacea: Squillidae): Allopatric diversification, secondary contact and hybridization

Mounting evidence of cryptic species in the marine realm emphasizes the necessity to thoroughly revise our current perceptions of marine biodiversity and species distributions. Here, we used mitochondrial cytochrome oxidase subunit I (mtDNA COI) and nuclear ribosomal internal transcribed spacer (nrDNA ITS) to investigate cryptic diversity and potential hybridization in the Japanese mantis shrimp Oratosquilla oratoria in the Northwestern (NW) Pacific. Both mitochondrial and nuclear gene genealogies revealed two cryptic species in this morphotaxon, which was further confirmed by extensive population-level analyses. One cryptic species is restricted to cold waters with a distribution range corresponding to temperate affinities, while the other dwelled warm waters influenced by the Kuroshio Current. Their divergence was postulated to be attributable to the vicariant event which resulted from the isolation of the Sea of Japan during the middle Pliocene (c. 3.85 Mya, 95% HPD 2.23–6.07 Mya). Allopatric speciation was maintained by limited genetic exchange due to their habitat preferences. Furthermore, the observation of recombinant nrDNA ITS sequence and intra-individual ITS polymorphism suggested recent hybridization event of the two cryptic species occurred in sympatric areas. Our study also illustrated that the Changjiang River outflow might act as an oceanic barrier to gene flow and promoted allopatric diversification in O. oratoria species complex.

Exploring Canadian Echinoderm Diversity through DNA Barcodes

DNA barcoding has proven an effective tool for species identification in varied groups of marine invertebrates including crustaceans, molluscs, polychaetes and echinoderms. In this study, we further validate its utility by analyzing almost half of the 300 species of Echinodermata known from Canadian waters. COI sequences from 999 specimens were assigned to 145 BINs. In most cases, species discrimination was straightforward due to the large difference (25-fold) between mean intra- (0.48%) and inter- (12.0%) specific divergence. Six species were flagged for further taxonomic investigation because specimens assigned to them fell into two or three discrete sequence clusters. The potential influence of larval dispersal capacity and glacial events on patterns of genetic diversity is discussed for 19 trans-oceanic species. Although additional research is needed to clarify biogeographic patterns and resolve taxonomic questions, this study represents an important step in the assembly of a DNA barcode library for all Canadian echinoderms, a valuable resource for future biosurveillance programs.

The use of DNA barcodes in food web construction-terrestrial and aquatic ecologists unite!

By depicting who eats whom, food webs offer descriptions of how groupings in nature (typically species or populations) are linked to each other. For asking questions on how food webs are built and work, we need descriptions of food webs at different levels of resolution. DNA techniques provide opportunities for highly resolved webs. In this paper, we offer an exposé of how DNA-based techniques, and DNA barcodes in particular, have recently been used to construct food web structure in both terrestrial and aquatic systems. We highlight how such techniques can be applied to simultaneously improve the taxonomic resolution of the nodes of the web (i.e., the species), and the links between them (i.e., who eats whom). We end by proposing how DNA barcodes and DNA information may allow new approaches to the construction of larger interaction webs, and overcome some hurdles to achieving adequate sample size. Most importantly, we propose that the joint adoption and development of these techniques may serve to unite approaches to food web studies in aquatic and terrestrial systems-revealing the extent to which food webs in these environments are structured similarly to or differently from each other, and how they are linked by dispersal.

Spectral absorption of visual pigments in stomatopod larval photoreceptors

Larval stomatopod eyes appear to be much simpler versions of adult compound eyes, lacking most of the visual pigment diversity and photoreceptor specializations. Our understanding of the visual pigment diversity of larval stomatopods, however, is based on four species, which severely limits our understanding of stomatopod eye ontogeny. To investigate several poorly understood aspects of stomatopod larval eye function, we tested two hypotheses surrounding the spectral absorption of larval visual pigments. First, we examined a broad range of species to determine if stomatopod larvae generally express a single, spectral class of photoreceptor. Using microspectrophotometry (MSP) on larvae captured in the field, we found data which further support this long-standing hypothesis. MSP was also used to test whether larval species from the same geographical region express visual pigments with similar absorption spectra. Interestingly, despite occupation of the same geographical location, we did not find evidence to support our second hypothesis. Rather, there was significant variation in visual pigment absorption spectra among sympatric species. These data are important to further our understanding of larval photoreceptor spectral diversity, which is beneficial to ongoing investigations into the ontogeny, physiology, and molecular evolution of stomatopod eyes.

Looking back on a decade of barcoding crustaceans

Species identification represents a pivotal component for large-scale biodiversity studies and conservation planning but represents a challenge for many taxa when using morphological traits only. Consequently, alternative identification methods based on molecular markers have been proposed. In this context, DNA barcoding has become a popular and accepted method for the identification of unknown animals across all life stages by comparison to a reference library. In this review we examine the progress of barcoding studies for the Crustacea using the Web of Science data base from 2003 to 2014. All references were classified in terms of taxonomy covered, subject area (identification/library, genetic variability, species descriptions, phylogenetics, methods, pseudogenes/numts), habitat, geographical area, authors, journals, citations, and the use of the Barcode of Life Data Systems (BOLD). Our analysis revealed a total number of 164 barcoding studies for crustaceans with a preference for malacostracan crustaceans, in particular Decapoda, and for building reference libraries in order to identify organisms. So far, BOLD did not establish itself as a popular informatics platform among carcinologists although it offers many advantages for standardized data storage, analyses and publication.

The Application of DNA Barcodes for the Identification of Marine Crustaceans from the North Sea and Adjacent Regions

During the last years DNA barcoding has become a popular method of choice for molecular specimen identification. Here we present a comprehensive DNA barcode library of various crustacean taxa found in the North Sea, one of the most extensively studied marine regions of the world. Our data set includes 1,332 barcodes covering 205 species, including taxa of the Amphipoda, Copepoda, Decapoda, Isopoda, Thecostraca, and others. This dataset represents the most extensive DNA barcode library of the Crustacea in terms of species number to date. By using the Barcode of Life Data Systems (BOLD), unique BINs were identified for 198 (96.6%) of the analyzed species. Six species were characterized by two BINs (2.9%), and three BINs were found for the amphipod species Gammarus salinus Spooner, 1947 (0.4%). Intraspecific distances with values higher than 2.2% were revealed for 13 species (6.3%). Exceptionally high distances of up to 14.87% between two distinct but monophyletic clusters were found for the parasitic copepod Caligus elongatus Nordmann, 1832, supporting the results of previous studies that indicated the existence of an overlooked sea louse species. In contrast to these high distances, haplotype-sharing was observed for two decapod spider crab species, Macropodia parva Van Noort & Adema, 1985 and Macropodia rostrata (Linnaeus, 1761), underlining the need for a taxonomic revision of both species. Summarizing the results, our study confirms the application of DNA barcodes as highly effective identification system for the analyzed marine crustaceans of the North Sea and represents an important milestone for modern biodiversity assessment studies using barcode sequences.

Metabarcoding is powerful yet still blind: a comparative analysis of morphological and molecular surveys of seagrass communities

In the context of the sixth wave of extinction, reliable surveys of biodiversity are increasingly needed to infer the cause and consequences of species and community declines, identify early warning indicators of tipping points, and provide reliable impact assessments before engaging in activities with potential environmental hazards. DNA metabarcoding has emerged as having potential to provide speedy assessment of community structure from environmental samples. Here we tested the reliability of metabarcoding by comparing morphological and molecular inventories of invertebrate communities associated with seagrasses through estimates of alpha and beta diversity, as well as the identification of the most abundant taxa. Sediment samples were collected from six Zostera marina seagrass meadows across Brittany, France. Metabarcoding surveys were performed using both mitochondrial (Cytochrome Oxidase I) and nuclear (small subunit 18S ribosomal RNA) markers, and compared to morphological inventories compiled by a long-term benthic monitoring network. A sampling strategy was defined to enhance performance and accuracy of results by preventing the dominance of larger animals, boosting statistical support through replicates, and using two genes to compensate for taxonomic biases. Molecular barcodes proved powerful by revealing a remarkable level of diversity that vastly exceeded the morphological survey, while both surveys identified congruent differentiation of the meadows. However, despite the addition of individual barcodes of common species into taxonomic reference databases, the retrieval of only 36% of these species suggest that the remaining were either not present in the molecular samples or not detected by the molecular screening. This finding exemplifies the necessity of comprehensive and well-curated taxonomic reference libraries and multi-gene surveys. Overall, results offer methodological guidelines and support for metabarcoding as a powerful and repeatable method of characterizing communities, while also presenting suggestions for improvement, including implementation of pilot studies prior to performing full "blind" metabarcoding assessments to optimize sampling and amplification protocols.

DNA barcoding of marine crustaceans from the Estuary and Gulf of St Lawrence: a regional-scale approach

Marine crustaceans are known as a group with a high level of morphological and ecological diversity but are difficult to identify by traditional approaches and usually require the help of highly trained taxonomists. A faster identification method, DNA barcoding, was found to be an effective tool for species identification in many metazoan groups including some crustaceans. Here we expand the DNA barcode database with a case study involving 80 malacostracan species from the Estuary and Gulf of St Lawrence. DNA sequences for 460 specimens grouped into clusters corresponding to known morphological species in 95% of cases. Genetic distances between species were on average 25 times higher than within species. Intraspecific divergence was high (3.78-13.6%) in specimens belonging to four morphological species, suggesting the occurrence of cryptic species. Moreover, we detected the presence of an invasive amphipod species in the St Lawrence Estuary. This study reconfirms the usefulness of DNA barcoding for the identification of marine crustaceans.

Compilation of morphological and molecular data, a necessity for taxonomy: The case of Hormogaster abbatissae sp. n. (Annelida, Clitellata, Hormogastridae)

Conflict among data sources can be frequent in evolutionary biology, especially in cases where one character set poses limitations to resolution. Earthworm taxonomy, for example, remains a challenge because of the limited number of morphological characters taxonomically valuable. An explanation to this may be morphological convergence due to adaptation to a homogeneous habitat, resulting in high degrees of homoplasy. This sometimes impedes clear morphological diagnosis of species. Combination of morphology with molecular techniques has recently aided taxonomy in many groups difficult to delimit morphologically. Here we apply an integrative approach by combining morphological and molecular data, including also some ecological features, to describe a new earthworm species in the family Hormogastridae, Hormogaster abbatissaesp. n., collected in Sant Joan de les Abadesses (Girona, Spain). Its anatomical and morphological characters are discussed in relation to the most similar Hormogastridae species, which are not the closest species in a phylogenetic analysis of molecular data. Species delimitation using the GMYC method and genetic divergences with the closest species are also considered. The information supplied by the morphological and molecular sources is contradictory, and thus we discuss issues with species delimitation in other similar situations. Decisions should be based on a profound knowledge of the morphology of the studied group but results from molecular analyses should also be considered.

Morphometric and molecular identification of individual barnacle cyprids from wild plankton: an approach to detecting fouling and invasive barnacle species

The present study used DNA barcodes to identify individual cyprids to species. This enables accurate quantification of larvae of potential fouling species in the plankton. In addition, it explains the settlement patterns of barnacles and serves as an early warning system of unwanted immigrant species. Sequences from a total of 540 individual cypris larvae from Taiwanese waters formed 36 monophyletic clades (species) in a phylogenetic tree. Of these clades, 26 were identified to species, but 10 unknown monophyletic clades represented non-native species. Cyprids of the invasive barnacle, Megabalanus cocopoma, were identified. Multivariate analysis of antennular morphometric characters revealed three significant clusters in a nMDS plot, viz. a bell-shaped attachment organ (most species), a shoe-shaped attachment organ (some species), and a spear-shaped attachment organ (coral barnacles only). These differences in attachment organ structure indicate that antennular structures interact directly with the diverse substrata involved in cirripede settlement.

An emergent science on the brink of irrelevance: a review of the past 8 years of DNA barcoding

DNA barcoding has become a well-funded, global enterprise since its proposition as a technique for species identification, delimitation and discovery in 2003. However, the rapid development of next generation sequencing (NGS) has the potential to render DNA barcoding irrelevant because of the speed with which it generates large volumes of genomic data. To avoid obsolescence, the DNA barcoding movement must adapt to use this new technology. This review examines the DNA barcoding enterprise, its continued resistance to improvement and the implications of this on the future of the discipline. We present the consistent failure of DNA barcoding to recognize its limitations and evolve its methodologies, reducing the usefulness of the data produced by the movement and throwing into doubt its ability to embrace NGS.

Future directions

It is a risky task to attempt to predict the direction that DNA barcoding and its applications may take in the future. In a very short time, the endeavor of DNA barcoding has gone from being a tool to facilitate taxonomy in difficult to identify species, to an ambitious, global initiative that seeks to tackle such pertinent and challenging issues as quantifying global biodiversity, revolutionizing the forensic identifications of species, advancing the study of interactions among species, and promoting the reconstruction of evolutionary relationships within communities. The core element of DNA barcoding will always remain the same: the generation of a set of well-identified samples collected and genotyped at one or more genetic barcode markers and assembled into a properly curated database. But the application of this body of data will depend on the creativity and need of the research community in using a "gold standard" of annotated DNA sequence data at the species level. We foresee several areas where the application of DNA barcode data is likely to yield important evolutionary, ecological, and societal insights, and while far from exclusive, provide examples of how DNA barcode data will continue to empower scientists to address hypothesis-driven research. Three areas of immediate and obvious concern are (1) biodiversity inventories, (2) phylogenetic applications, and (3) species interactions.

Recent discoveries of armyworms in Japan and their species identification using DNA barcoding

Long columns of migrating larval sciarid armyworms were discovered in central and northern Japan, specifically Kanagawa, Gunma, Miyagi and Akita prefectures, as well as Hokkaido. This is the first examination of armyworms in East Asia. In Europe, armyworms have been identified as Sciara militaris, belonging to the family Sciaridae (sciarid flies or black fungus gnats), by rearing them to adulthood. In Japan, we were unable to obtain live samples for rearing; therefore, DNA barcodes were obtained from the samples of armyworms collected in the Gunma and Miyagi prefectures. The DNA barcodes were compared with those obtained from the following samples: pupae of S. militaris from UK, adults of Sciara kitakamiensis, Sciara humeralis, Sciara hemerobioides, Sciara thoracica, Sciara helvola and Sciara melanostyla from Japan, and adults of one undescribed Sciara species from Malaysia. Neighbour-joining, maximum parsimony, and maximum likelihood analyses revealed that the armyworms discovered in Japan are S. kitakamiensis. Although adults of this species have been recorded in several locations in Japan, this is the first report of migrating larval armyworms. DNA barcodes were effectively used to link different life stages of this species. The average intraspecific and interspecific pairwise genetic distances of the genus Sciara were 0.3% and 12.6%, respectively. The present study illustrates that DNA barcodes are an effective means of identifying sciarid flies in Japan.

Barcode haplotype variation in north American agroecosystem lady beetles (Coleoptera: Coccinellidae)

DNA barcodes have proven invaluable in identifying and distinguishing insect pests, most notably for determining the provenance of exotic invasives, but relatively few insect natural enemies have been barcoded. We used Folmer et al.'s (1994) universal invertebrate primers and Hebert et al.'s (2004) for Lepidoptera, to amplify 658 bp at the 5' end of the mitochondrial cytochrome oxidase c subunit I (COI) gene in five species of lady beetles from crop fields in six states in the US Mid-Atlantic, Plains and Midwest: three native species, Hippodamia convergens Guérin-Méneville, H. parenthesis (Say) and Coleomegilla maculata (De Geer); and two exotic species, Harmonia axyridis (Pallas) and Coccinella septempunctata Linnaeus. Sequence divergences within species were low, never exceeding 0.9% (Kimura 2-parameter distances). Sequence divergences between the two Hippodamia species ranged from 14.7 to 16.4%, mirroring the relationships found for other arthropod taxa. Among the exotic species, C. septempunctata sequences were as variable as those of the three native species, while H. axyridis populations comprised a single haplotype. Limited data on two Coleomegilla subspecies, C. m. lengi Timberlake and C. m. fuscilabris (Mulsant), are consistent with their belonging to the same species, although morphological and reproductive data indicate that they represent separate species. Our results support the general utility of COI barcodes for distinguishing and diagnosing coccinellid species, but point to possible limitations in the use of barcodes to resolve species assignments in recently divergent sibling species.

Cytochrome c oxidase subunit 1 barcode data of fish of the Nayband National Park in the Persian Gulf and analysis using meta-data flag several cryptic species

We provide cytochrome c oxidase subunit 1 (COI) barcode sequences of fishes of the Nayband National Park, Persian Gulf, Iran. Industrial activities, ecological considerations and goals of The Fish Barcode of Life campaign make it crucial that fish species residing in the park be identified. To the best of our knowledge, this is the first report of barcoding data on fishes of the Persian Gulf. We examined 187 individuals representing 76 species, 56 genera and 32 families. The data flagged potentially cryptic species of Gerres filamentosus and Plectorhinchus schotaf. 16S rDNA data on these species are provided. Exclusion of these two potential cryptic species resulted in a mean COI intraspecific distance of 0.18%, and a mean inter- to intraspecific divergence ratio of 66.7. There was no overlap between maximum Kimura 2-parameter distances among conspecifics (1.66%) and minimum distance among congeneric species (6.19%). Barcodes shared among species were not observed. Neighbour-joining analysis showed that most species formed cohesive sequence units with little variation. Finally, the comparison of 16 selected species from this study with meta-data of conspecifics from Australia, India, China and South Africa revealed high interregion divergences and potential existence of six cryptic species. Pairwise interregional comparisons were more informative than global divergence assessments with regard to detection of cryptic variation. Our analysis exemplifies optimal use of the expanding barcode data now becoming available.

DNA barcoding of marine metazoa

More than 230,000 known species representing 31 metazoan phyla populate the world's oceans. Perhaps another 1,000,000 or more species remain to be discovered. There is reason for concern that species extinctions may out-pace discovery, especially in diverse and endangered marine habitats such as coral reefs. DNA barcodes (i.e., short DNA sequences for species recognition and discrimination) are useful tools to accelerate species-level analysis of marine biodiversity and to facilitate conservation efforts. This review focuses on the usual barcode region for metazoans: a approximately 648 base-pair region of the mitochondrial cytochrome c oxidase subunit I (COI) gene. Barcodes have also been used for population genetic and phylogeographic analysis, identification of prey in gut contents, detection of invasive species, forensics, and seafood safety. More controversially, barcodes have been used to delimit species boundaries, reveal cryptic species, and discover new species. Emerging frontiers are the use of barcodes for rapid and increasingly automated biodiversity assessment by high-throughput sequencing, including environmental barcoding and the use of barcodes to detect species for which formal identification or scientific naming may never be possible.

Complete DNA barcode reference library for a country's butterfly fauna reveals high performance for temperate Europe

DNA barcoding aims to accelerate species identification and discovery, but performance tests have shown marked differences in identification success. As a consequence, there remains a great need for comprehensive studies which objectively test the method in groups with a solid taxonomic framework. This study focuses on the 180 species of butterflies in Romania, accounting for about one third of the European butterfly fauna. This country includes five eco-regions, the highest of any in the European Union, and is a good representative for temperate areas. Morphology and DNA barcodes of more than 1300 specimens were carefully studied and compared. Our results indicate that 90 per cent of the species form barcode clusters allowing their reliable identification. The remaining cases involve nine closely related species pairs, some whose taxonomic status is controversial or that hybridize regularly. Interestingly, DNA barcoding was found to be the most effective identification tool, outperforming external morphology, and being slightly better than male genitalia. Romania is now the first country to have a comprehensive DNA barcode reference database for butterflies. Similar barcoding efforts based on comprehensive sampling of specific geographical regions can act as functional modules that will foster the early application of DNA barcoding while a global system is under development.

An in silico approach for the evaluation of DNA barcodes

BACKGROUND

DNA barcoding is a key tool for assessing biodiversity in both taxonomic and environmental studies. Essential features of barcodes include their applicability to a wide spectrum of taxa and their ability to identify even closely related species. Several DNA regions have been proposed as barcodes and the region selected strongly influences the output of a study. However, formal comparisons between barcodes remained limited until now. Here we present a standard method for evaluating barcode quality, based on the use of a new bioinformatic tool that performs in silico PCR over large databases. We illustrate this approach by comparing the taxonomic coverage and the resolution of several DNA regions already proposed for the barcoding of vertebrates. To assess the relationship between in silico and in vitro PCR, we also developed specific primers amplifying different species of Felidae, and we tested them using both kinds of PCR RESULTS: Tests on specific primers confirmed the correspondence between in silico and in vitro PCR. Nevertheless, results of in silico and in vitro PCRs can be somehow different, also because tuning PCR conditions can increase the performance of primers with limited taxonomic coverage. The in silico evaluation of DNA barcodes showed a strong variation of taxonomic coverage (i.e., universality): barcodes based on highly degenerated primers and those corresponding to the conserved region of the Cyt-b showed the highest coverage. As expected, longer barcodes had a better resolution than shorter ones, which are however more convenient for ecological studies analysing environmental samples.

CONCLUSIONS

In silico PCR could be used to improve the performance of a study, by allowing the preliminary comparison of several DNA regions in order to identify the most appropriate barcode depending on the study aims.

Mitochondrial heteroplasmy and DNA barcoding in Hawaiian Hylaeus (Nesoprosopis) bees (Hymenoptera: Colletidae)

BACKGROUND

The past several years have seen a flurry of papers seeking to clarify the utility and limits of DNA barcoding, particularly in areas such as species discovery and paralogy due to nuclear pseudogenes. Heteroplasmy, the coexistence of multiple mitochondrial haplotypes in a single organism, has been cited as a potentially serious problem for DNA barcoding but its effect on identification accuracy has not been tested. In addition, few studies of barcoding have tested a large group of closely-related species with a well-established morphological taxonomy. In this study we examine both of these issues, by densely sampling the Hawaiian Hylaeus bee radiation.

RESULTS

Individuals from 21 of the 49 a priori morphologically-defined species exhibited coding sequence heteroplasmy at levels of 1-6% or more. All homoplasmic species were successfully identified by COI using standard methods of analysis, but only 71% of heteroplasmic species. The success rate in identifying heteroplasmic species was increased to 86% by treating polymorphisms as character states rather than ambiguities. Nuclear pseudogenes (numts) were also present in four species, and were distinguishable from heteroplasmic sequences by patterns of nucleotide and amino acid change.

CONCLUSIONS

Heteroplasmy significantly decreased the reliability of species identification. In addition, the practical issue of dealing with large numbers of polymorphisms- and resulting increased time and labor required - makes the development of DNA barcode databases considerably more complex than has previously been suggested. The impact of heteroplasmy on the utility of DNA barcoding as a bulk specimen identification tool will depend upon its frequency across populations, which remains unknown. However, DNA barcoding is still likely to remain an important identification tool for those species that are difficult or impossible to identify through morphology, as is the case for the ecologically important solitary bee fauna.

Four new species of Plasmodium from New Guinea lizards: integrating morphology and molecules

New Guinea is one of the most biodiverse regions of the world, particularly in terms of the herpetofauna present, yet surprisingly little is known about the parasites that infect these organisms. A survey of diverse scinid and agamid lizard hosts from this country showed a diversity of malaria parasites infecting these hosts. We combined morphological and morphometric observations of the parasites (primarily gametocytes) along with DNA sequence data from the mitochondrial cytochrome b and cytochrome oxidase I genes and here describe 4 new species of Plasmodium, i.e. Plasmodium minuoviride n. sp., Plasmodium koreafense n. sp., Plasmodium megalotrypa n. sp., and Plasmodium gemini n. sp. A fifth species, Plasmodium lacertiliae Thompson and Hart 1946, is redescribed based on new observations of hosts and localities and additional molecular data. This combined morphological and molecular approach is advised for all future descriptions of new malaria parasite species, particularly in light of situations where every life-history stage is not available.

Tissue segregation of mitochondrial haplotypes in heteroplasmic Hawaiian bees: implications for DNA barcoding

The issue of mitochondrial heteroplasmy has been cited as a theoretical problem for DNA barcoding but is only beginning to be examined in natural systems. We sequenced multiple DNA extractions from 20 individuals of four Hawaiian Hylaeus bee species known to be heteroplasmic. All species showed strong differences at polymorphic sites between abdominal and muscle tissue in most individuals, and only two individuals had no obvious segregation. Two specimens produced completely clean sequences from abdominal DNA. The fact that these differences are clearly visible by direct sequencing indicates that substantial intra-individual mtDNA diversity may be overlooked when DNA is taken from small tissue fragments. At the same time, differences in haplotype distribution among individuals may result in incorrect recognition of cryptic species. Because DNA barcoding studies typically use only a small fragment of an organism, they are particularly vulnerable to sequencing bias where heteroplasmy and haplotype segregation are present. It is important to anticipate this possibility prior to undertaking large-scale barcoding projects to reduce the likelihood of haplotype segregation confounding the results.

Phylogeography and limited genetic connectivity in the endangered boring giant clam across the Coral Triangle

The Coral Triangle is the global center of marine biodiversity; however, its coral reefs are critically threatened. Because of the bipartite life history of many marine species with sedentary adults and dispersive pelagic larvae, designing effective marine protected areas requires an understanding of patterns of larval dispersal and connectivity among geographically discrete populations. We used mtDNA sequence data to examine patterns of genetic connectivity in the boring giant clam (Tridacna crocea) in an effort to guide conservation efforts within the Coral Triangle. We collected an approximately 485 base pair fragment of mtDNA cytochrome c oxidase 1 (CO1) from 414 individuals at 26 sites across Indonesia. Genetic structure was strong between regions (phi(ST)=0.549, p < 0.00001) with 3 strongly supported clades: one restricted to western Sumatra, another distributed across central Indonesia, and a third limited to eastern Indonesia and Papua. Even within the single largest clade, small but significant genetic structure was documented (phi(ST)=0.069, p < 0.00001), which indicates limited gene flow within and among phylogeographic regions. Significant patterns of isolation by distance indicated an average dispersal distance of only 25-50 km, which is far below dispersal predictions of 406-708 km derived from estimates of passive dispersal over 10 days via surface currents. The strong regional genetic structure we found indicates potent limits to genetic and demographic connectivity for this species throughout the Coral Triangle and provides a regional context for conservation planning. The recovery of 3 distinct evolutionarily significant units within a well-studied taxonomic group suggests that biodiversity in this region may be significantly underestimated and that Tridacna taxa may be more endangered than currently recognized.

Endemism and regional color and genetic differences in five putatively cosmopolitan reef fishes

Endemism is thought to be relatively rare in marine systems due to the lack of allopatric barriers and the potential for long-distance colonization via pelagic larval dispersal. Although many species of coral reef fishes exhibit regionally restricted color variants that are suggestive of regional endemism, such variation is typically ascribed to intraspecific variation. We examined the genetic structure in 5 putatively monospecific fishes from the Indo-West Pacific (Amphiprion melanopus, Chrysiptera talboti, and Pomacentrus moluccensis [Pomacentridae] and Cirrhilabrus punctatus, and Labroides dimidiatus [Labridae]) that express regional color variation unique to this area. Mitochondrial-control-region sequence analysis showed shallow to deep genetic divergence in all 5 species (sequence divergence 2-17%), with clades concordant with regional color variation. These results were partially supported by nuclear RAG2 data. An analysis of molecular variation (AMOVA) mirrored the phylogenetic results; Phi(ST) values ranged from 0.91 to 0.7, indicating high levels of geographic partitioning of genetic variation. Concordance of genetics and phenotype demonstrate the genetic uniqueness of southwestern Pacific color variants, indicating that these populations are at a minimum distinct evolutionarily significant units and perhaps distinct regionally endemic species. Our results indicate that the alpha biodiversity of the southwestern Pacific is likely underestimated even in well-studied groups, such as reef fishes, and that regional endemism may be more common in tropical marine systems than previously thought.

Identifying Canadian freshwater fishes through DNA barcodes

BACKGROUND

DNA barcoding aims to provide an efficient method for species-level identifications using an array of species specific molecular tags derived from the 5' region of the mitochondrial cytochrome c oxidase I (COI) gene. The efficiency of the method hinges on the degree of sequence divergence among species and species-level identifications are relatively straightforward when the average genetic distance among individuals within a species does not exceed the average genetic distance between sister species. Fishes constitute a highly diverse group of vertebrates that exhibit deep phenotypic changes during development. In this context, the identification of fish species is challenging and DNA barcoding provide new perspectives in ecology and systematics of fishes. Here we examined the degree to which DNA barcoding discriminate freshwater fish species from the well-known Canadian fauna, which currently encompasses nearly 200 species, some which are of high economic value like salmons and sturgeons.

METHODOLOGY/PRINCIPAL FINDINGS

We bi-directionally sequenced the standard 652 bp "barcode" region of COI for 1360 individuals belonging to 190 of the 203 Canadian freshwater fish species (95%). Most species were represented by multiple individuals (7.6 on average), the majority of which were retained as voucher specimens. The average genetic distance was 27 fold higher between species than within species, as K2P distance estimates averaged 8.3% among congeners and only 0.3% among concpecifics. However, shared polymorphism between sister-species was detected in 15 species (8% of the cases). The distribution of K2P distance between individuals and species overlapped and identifications were only possible to species group using DNA barcodes in these cases. Conversely, deep hidden genetic divergence was revealed within two species, suggesting the presence of cryptic species.

CONCLUSIONS/SIGNIFICANCE

The present study evidenced that freshwater fish species can be efficiently identified through the use of DNA barcoding, especially the species complex of small-sized species, and that the present COI library can be used for subsequent applications in ecology and systematics.

DNA microarrays for identifying fishes

In many cases marine organisms and especially their diverse developmental stages are difficult to identify by morphological characters. DNA-based identification methods offer an analytically powerful addition or even an alternative. In this study, a DNA microarray has been developed to be able to investigate its potential as a tool for the identification of fish species from European seas based on mitochondrial 16S rDNA sequences. Eleven commercially important fish species were selected for a first prototype. Oligonucleotide probes were designed based on the 16S rDNA sequences obtained from 230 individuals of 27 fish species. In addition, more than 1200 sequences of 380 species served as sequence background against which the specificity of the probes was tested in silico. Single target hybridisations with Cy5-labelled, PCR-amplified 16S rDNA fragments from each of the 11 species on microarrays containing the complete set of probes confirmed their suitability. True-positive, fluorescence signals obtained were at least one order of magnitude stronger than false-positive cross-hybridisations. Single nontarget hybridisations resulted in cross-hybridisation signals at approximately 27% of the cases tested, but all of them were at least one order of magnitude lower than true-positive signals. This study demonstrates that the 16S rDNA gene is suitable for designing oligonucleotide probes, which can be used to differentiate 11 fish species. These data are a solid basis for the second step to create a "Fish Chip" for approximately 50 fish species relevant in marine environmental and fisheries research, as well as control of fisheries products.

Utility of DNA taxonomy and barcoding for the inference of larval community structure in morphologically cryptic Chironomus (Diptera) species

Biodiversity studies require species level analyses for the accurate assessment of community structures. However, while specialized taxonomic knowledge is only rarely available for routine identifications, DNA taxonomy and DNA barcoding could provide the taxonomic basis for ecological inferences. In this study, we assessed the community structure of sediment dwelling, morphologically cryptic Chironomus larvae in the Rhine-valley plain/Germany, comparing larval type classification, cytotaxonomy, DNA taxonomy and barcoding. While larval type classification performed poorly, cytotaxonomy and DNA-based methods yielded comparable results: detrended correspondence analysis and permutation analyses indicated that the assemblages are not randomly but competitively structured. However, DNA taxonomy identified an additional species that could not be resolved by the traditional method. We argue that DNA-based identification methods such as DNA barcoding can be a valuable tool to increase accuracy, objectivity and comparability of the taxonomic assessment in biodiversity and community ecology studies.