Integrating DNA barcode data and taxonomic practice: Determination, discovery, and description

Australian Sphingidae--DNA barcodes challenge current species boundaries and distributions

MAIN OBJECTIVE

We examine the extent of taxonomic and biogeographical uncertainty in a well-studied group of Australian Lepidoptera, the hawkmoths (Sphingidae).

METHODS

We analysed the diversity of Australian sphingids through the comparative analysis of their DNA barcodes, supplemented by morphological re-examinations and sequence information from a nuclear marker in selected cases. The results from the analysis of Australian sphingids were placed in a broader context by including conspecifics and closely related taxa from outside Australia to test taxonomic boundaries.

RESULTS

Our results led to the discovery of six new species in Australia, one case of erroneously synonymized species, and three cases of synonymy. As a result, we establish the occurrence of 75 species of hawkmoths on the continent. The analysis of records from outside Australia also challenges the validity of current taxonomic boundaries in as many as 18 species, including Agrius convolvuli (Linnaeus, 1758), a common species that has gained adoption as a model system. Our work has revealed a higher level of endemism than previously recognized. Most (90%) Australian sphingids are endemic to the continent (45%) or to Australia, the Pacific Islands and the Papuan and Wallacean regions (45%). Only seven species (10%) have ranges that extend beyond this major biogeographical boundary toward SE Asia and other regions of the Old World.

MAIN CONCLUSIONS

This study has established that overlooked cryptic diversity and inaccurate species delineation produced significant misconceptions concerning diversity and distribution patterns in a group of insects that is considered well known taxonomically. Because DNA barcoding represents a straightforward way to test taxonomic boundaries, its implementation can improve the accuracy of primary diversity data in biogeography and conservation studies.

DNA barcoding of marine copepods: assessment of analytical approaches to species identification

More than 2,500 species of copepods (Class Maxillopoda; Subclass Copepoda) occur in the marine planktonic environment. The exceptional morphological conservation of the group, with numerous sibling species groups, makes the identification of species challenging, even for expert taxonomists. Molecular approaches to species identification have allowed rapid detection, discrimination, and identification of species based on DNA sequencing of single specimens and environmental samples. Despite the recent development of diverse genetic and genomic markers, the barcode region of the mitochondrial cytochrome c oxidase subunit I (COI) gene remains a useful and - in some cases - unequaled diagnostic character for species-level identification of copepods. This study reports 800 new barcode sequences for 63 copepod species not included in any previous study and examines the reliability and resolution of diverse statistical approaches to species identification based upon a dataset of 1,381 barcode sequences for 195 copepod species. We explore the impact of missing data (i.e., species not represented in the barcode database) on the accuracy and reliability of species identifications. Among the tested approaches, the best close match analysis resulted in accurate identification of all individuals to species, with no errors (false positives), and out-performed automated tree-based or BLAST based analyses. This comparative analysis yields new understanding of the strengths and weaknesses of DNA barcoding and confirms the value of DNA barcodes for species identification of copepods, including both individual specimens and bulk samples. Continued integrative morphological-molecular taxonomic analysis is needed to produce a taxonomically-comprehensive database of barcode sequences for all species of marine copepods.

DNA barcoding of Murinae (Rodentia: Muridae) and Arvicolinae (Rodentia: Cricetidae) distributed in China

Identification of rodents is very difficult mainly due to high similarities in morphology and controversial taxonomy. In this study, mitochondrial cytochrome oxidase subunit I (COI) was used as DNA barcode to identify the Murinae and Arvicolinae species distributed in China and to facilitate the systematics studies of Rodentia. In total, 242 sequences (31 species, 11 genera) from Murinae and 130 sequences (23 species, 6 genera) from Arvicolinae were investigated, of which 90 individuals were novel. Genetic distance, threshold method, tree-based method, online BLAST and BLOG were employed to analyse the data sets. There was no obvious barcode gap. The average K2P distance within species and genera was 2.10% and 12.61% in Murinae, and 2.86% and 11.80% in Arvicolinae, respectively. The optimal threshold was 5.62% for Murinae and 3.34% for Arvicolinae. All phylogenetic trees exhibited similar topology and could distinguish 90.32% of surveyed species in Murinae and 82.60% in Arvicolinae with high support values. BLAST analyses yielded similar results with identification success rates of 92.15% and 93.85% for Murinae and Arvicolinae, respectively. BLOG successfully authenticated 100% of detected species except Leopoldamys edwardsi based on the latest taxonomic revision. Our results support the species status of recently recognized Micromys erythrotis, Eothenomys tarquinius and E. hintoni and confirm the important roles of comprehensive taxonomy and accurate morphological identification in DNA barcoding studies. We believe that, when proper analytic methods are applied or combined, DNA barcoding could serve as an accurate and effective species identification approach for Murinae and Arvicolinae based on a proper taxonomic framework.

What is biodiversity? Stepping forward from barcoding to understanding biological differences

This opinion paper gives personal views of the direction that cataloguing biodiversity should be going in. Although molecular taxonomy enables rapid and high throughput identification of species, it needs to be anchored to traditional taxonomy, because without information of actual biological properties of species, DNA barcoding just reports differences in selected DNA sequences, which need not have anything to do with the biological properties of the organisms, and the reasons for the development of the species. Since functional differences are the most common reason behind species differences, the future of cataloguing biodiversity and biodiversity research is, in my opinion, in trying to integrate genomic research to comparative physiology in order to be able to evaluate which functional properties have likely been important in generating biodiversity. This task is overwhelming, and requires forgetting the traditional disciplines. Further, major problems associated with the present-day treatment of genomic data are presented from my viewpoint.

Advances in taxonomy of genus phoma: polyphyletic nature and role of phenotypic traits and molecular systematics

Phoma is a highly polyphyletic genus with its unclear species boundaries. The conventional system of identification is functional but it has its limitations. Besides morphological studies, chemotaxonomy, secondary metabolite and protein profiling have been assessed for the classification and identification of these fungi. Molecular datasets have provided a better outlook towards the phylogenetic and evolutionary trends of Phoma. Molecular markers such as ITS-rDNA, tubulin, actin, translation elongation factor have been widely used by the taxonomists to demarcate species. However, outcomes gained up till now represent preliminary step towards the study of Phoma systematics and a combined approach would be beneficial in the understanding of this polyphyletic group members. Lately, on the base of molecular phylogeny of the type species of the seven Phoma sections a new teleomorph family, Didymellaceae has been established, besides the Phaeosphaeriaceae related to sect. Paraphoma anamorphs, and the Leptosphaeriaceae to sect. Heterospora anamorphs. The estimated ratio is about 70 % of the recognized Phoma-like species can be associated with the Didymellaceae ascomycetous family.

Which specimens from a museum collection will yield DNA barcodes? A time series study of spiders in alcohol

We report initial results from an ongoing effort to build a library of DNA barcode sequences for Dutch spiders and investigate the utility of museum collections as a source of specimens for barcoding spiders. Source material for the library comes from a combination of specimens freshly collected in the field specifically for this project and museum specimens collected in the past. For the museum specimens, we focus on 31 species that have been frequently collected over the past several decades. A series of progressively older specimens representing these 31 species were selected for DNA barcoding. Based on the pattern of sequencing successes and failures, we find that smaller-bodied species expire before larger-bodied species as tissue sources for single-PCR standard DNA barcoding. Body size and age of oldest successful DNA barcode are significantly correlated after factoring out phylogenetic effects using independent contrasts analysis. We found some evidence that extracted DNA concentration is correlated with body size and inversely correlated with time since collection, but these relationships are neither strong nor consistent. DNA was extracted from all specimens using standard destructive techniques involving the removal and grinding of tissue. A subset of specimens was selected to evaluate nondestructive extraction. Nondestructive extractions significantly extended the DNA barcoding shelf life of museum specimens, especially small-bodied species, and yielded higher DNA concentrations compared to destructive extractions. All primary data are publically available through a Dryad archive and the Barcode of Life database.

Genetic patterns in European geometrid moths revealed by the Barcode Index Number (BIN) system

Background

The geometrid moths of Europe are one of the best investigated insect groups in traditional taxonomy making them an ideal model group to test the accuracy of the Barcode Index Number (BIN) system of BOLD (Barcode of Life Datasystems), a method that supports automated, rapid species delineation and identification.

Methodology/Principal Findings

This study provides a DNA barcode library for 219 of the 249 European geometrid moth species (88%) in five selected subfamilies. The data set includes COI sequences for 2130 specimens. Most species (93%) were found to possess diagnostic barcode sequences at the European level while only three species pairs (3%) were genetically indistinguishable in areas of sympatry. As a consequence, 97% of the European species we examined were unequivocally discriminated by barcodes within their natural areas of distribution. We found a 1:1 correspondence between BINs and traditionally recognized species for 67% of these species. Another 17% of the species (15 pairs, three triads) shared BINs, while specimens from the remaining species (18%) were divided among two or more BINs. Five of these species are mixtures, both sharing and splitting BINs. For 82% of the species with two or more BINs, the genetic splits involved allopatric populations, many of which have previously been hypothesized to represent distinct species or subspecies.

Conclusions/Significance

This study confirms the effectiveness of DNA barcoding as a tool for species identification and illustrates the potential of the BIN system to characterize formal genetic units independently of an existing classification. This suggests the system can be used to efficiently assess the biodiversity of large, poorly known assemblages of organisms. For the moths examined in this study, cases of discordance between traditionally recognized species and BINs arose from several causes including overlooked species, synonymy, and cases where DNA barcodes revealed regional variation of uncertain taxonomic significance.

A simple shortcut to unsupervised alignment-free phylogenetic genome groupings, even from unassembled sequencing reads

We propose an extension to alignment-free approaches that can produce reasonably accurate phylogenetic groupings starting from unaligned genomes, for example, as fast as 1 min on a standard desktop computer for 25 bacterial genomes. A 6-fold speed-up and 11-fold reduction in memory requirements compared to previous alignment-free methods is achieved by reducing the comparison space to a representative sample of k-mers of optimal length and with specific tag motifs. This approach was applied to the test case of fitting the enterohemorrhagic O104:H4 E.coli strain from the 2011 outbreak in Germany into the phylogenetic network of previously known E.coli-related strains and extend the method to allow assigning any new strain to the correct phylogenetic group even directly from unassembled short sequence reads from next generation sequencing data. Hence, this approach is also useful to quickly identify the most suitable reference genome for subsequent assembly steps.

A general species delimitation method with applications to phylogenetic placements

MOTIVATION

Sequence-based methods to delimit species are central to DNA taxonomy, microbial community surveys and DNA metabarcoding studies. Current approaches either rely on simple sequence similarity thresholds (OTU-picking) or on complex and compute-intensive evolutionary models. The OTU-picking methods scale well on large datasets, but the results are highly sensitive to the similarity threshold. Coalescent-based species delimitation approaches often rely on Bayesian statistics and Markov Chain Monte Carlo sampling, and can therefore only be applied to small datasets.

RESULTS

We introduce the Poisson tree processes (PTP) model to infer putative species boundaries on a given phylogenetic input tree. We also integrate PTP with our evolutionary placement algorithm (EPA-PTP) to count the number of species in phylogenetic placements. We compare our approaches with popular OTU-picking methods and the General Mixed Yule Coalescent (GMYC) model. For de novo species delimitation, the stand-alone PTP model generally outperforms GYMC as well as OTU-picking methods when evolutionary distances between species are small. PTP neither requires an ultrametric input tree nor a sequence similarity threshold as input. In the open reference species delimitation approach, EPA-PTP yields more accurate results than de novo species delimitation methods. Finally, EPA-PTP scales on large datasets because it relies on the parallel implementations of the EPA and RAxML, thereby allowing to delimit species in high-throughput sequencing data.

AVAILABILITY AND IMPLEMENTATION

The code is freely available at www.exelixis-lab.org/software.html. .

A retrospective approach to testing the DNA barcoding method

A decade ago, DNA barcoding was proposed as a standardised method for identifying existing species and speeding the discovery of new species. Yet, despite its numerous successes across a range of taxa, its frequent failures have brought into question its accuracy as a short-cut taxonomic method. We use a retrospective approach, applying the method to the classification of New Zealand skinks as it stood in 1977 (primarily based upon morphological characters), and compare it to the current taxonomy reached using both morphological and molecular approaches. For the 1977 dataset, DNA barcoding had moderate-high success in identifying specimens (78-98%), and correctly flagging specimens that have since been confirmed as distinct taxa (77-100%). But most matching methods failed to detect the species complexes that were present in 1977. For the current dataset, there was moderate-high success in identifying specimens (53-99%). For both datasets, the capacity to discover new species was dependent on the methodological approach used. Species delimitation in New Zealand skinks was hindered by the absence of either a local or global barcoding gap, a result of recent speciation events and hybridisation. Whilst DNA barcoding is potentially useful for specimen identification and species discovery in New Zealand skinks, its error rate could hinder the progress of documenting biodiversity in this group. We suggest that integrated taxonomic approaches are more effective at discovering and describing biodiversity.

DNA barcoding of sigmodontine rodents: identifying wildlife reservoirs of zoonoses

Species identification through DNA barcoding is a tool to be added to taxonomic procedures, once it has been validated. Applying barcoding techniques in public health would aid in the identification and correct delimitation of the distribution of rodents from the subfamily Sigmodontinae. These rodents are reservoirs of etiological agents of zoonoses including arenaviruses, hantaviruses, Chagas disease and leishmaniasis. In this study we compared distance-based and probabilistic phylogenetic inference methods to evaluate the performance of cytochrome c oxidase subunit I (COI) in sigmodontine identification. A total of 130 sequences from 21 field-trapped species (13 genera), mainly from southern Brazil, were generated and analyzed, together with 58 GenBank sequences (24 species; 10 genera). Preliminary analysis revealed a 9.5% rate of misidentifications in the field, mainly of juveniles, which were reclassified after examination of external morphological characters and chromosome numbers. Distance and model-based methods of tree reconstruction retrieved similar topologies and monophyly for most species. Kernel density estimation of the distance distribution showed a clear barcoding gap with overlapping of intraspecific and interspecific densities < 1% and 21 species with mean intraspecific distance < 2%. Five species that are reservoirs of hantaviruses could be identified through DNA barcodes. Additionally, we provide information for the description of a putative new species, as well as the first COI sequence of the recently described genus Drymoreomys. The data also indicated an expansion of the distribution of Calomys tener. We emphasize that DNA barcoding should be used in combination with other taxonomic and systematic procedures in an integrative framework and based on properly identified museum collections, to improve identification procedures, especially in epidemiological surveillance and ecological assessments.

How to describe a cryptic species? Practical challenges of molecular taxonomy

BACKGROUND

Molecular methods of species delineation are rapidly developing and widely considered as fast and efficient means to discover species and face the 'taxonomic impediment' in times of biodiversity crisis. So far, however, this form of DNA taxonomy frequently remains incomplete, lacking the final step of formal species description, thus enhancing rather than reducing impediments in taxonomy. DNA sequence information contributes valuable diagnostic characters and -at least for cryptic species - could even serve as the backbone of a taxonomic description. To this end solutions for a number of practical problems must be found, including a way in which molecular data can be presented to fulfill the formal requirements every description must meet. Multi-gene barcoding and a combined molecular species delineation approach recently revealed a radiation of at least 12 more or less cryptic species in the marine meiofaunal slug genus Pontohedyle (Acochlidia, Heterobranchia). All identified candidate species are well delimited by a consensus across different methods based on mitochondrial and nuclear markers.

RESULTS

The detailed microanatomical redescription of Pontohedyle verrucosa provided in the present paper does not reveal reliable characters for diagnosing even the two major clades identified within the genus on molecular data. We thus characterize three previously valid Pontohedyle species based on four genetic markers (mitochondrial cytochrome c oxidase subunit I, 16S rRNA, nuclear 28S and 18S rRNA) and formally describe nine cryptic new species (P. kepii sp. nov., P. joni sp. nov., P. neridae sp. nov., P. liliae sp. nov., P. wiggi sp. nov., P. wenzli sp. nov., P. peteryalli sp. nov., P. martynovi sp. nov., P. yurihookeri sp. nov.) applying molecular taxonomy, based on diagnostic nucleotides in DNA sequences of the four markers. Due to the minute size of the animals, entire specimens were used for extraction, consequently the holotype is a voucher of extracted DNA ('DNA-type'). We used the Character Attribute Organization System (CAOS) to determine diagnostic nucleotides, explore the dependence on input data and data processing, and aim for maximum traceability in our diagnoses for future research. Challenges, pitfalls and necessary considerations for applied DNA taxonomy are critically evaluated.

CONCLUSIONS

To describe cryptic species traditional lines of evidence in taxonomy need to be modified. DNA sequence information, for example, could even serve as the backbone of a taxonomic description. The present contribution demonstrates that few adaptations are needed to integrate into traditional taxonomy novel diagnoses based on molecular data. The taxonomic community is encouraged to join the discussion and develop a quality standard for molecular taxonomy, ideally in the form of an automated final step in molecular species delineation procedures.

Diversity of Aplochiton fishes (Galaxiidea) and the taxonomic resurrection of A. marinus

Aplochiton is a small genus of galaxiid fishes endemic to Patagonia and the Falkland Islands whose taxonomy is insufficiently resolved. Recent genetic analyses confirmed the existence of only two closely related species, Aplochiton taeniatus and Aplochiton zebra, while a third controversial species, Aplochiton marinus, remained lost to synonymy with A. taeniatus. Using an integrative taxonomy framework, we studied original samples and published sequences from a broad range in western Patagonia and the Falkland Islands, and generated robust species hypotheses based on single-locus (Cytochrome Oxidase subunit I; COI) species-delineation methods and known diagnostic morphological characters analyzed in a multivariate context. Results revealed three distinct evolutionary lineages that morphologically resemble, in important respects, existing nominal species descriptions. Interestingly, the lineage associated with A. marinus was unambiguously identifiable (100% accuracy) both from the genetic and morphological viewpoints. In contrast, the morphology of A. taeniatus and A. zebra overlapped substantially, mainly due to the high variability of A. taeniatus. Discriminant function analysis aided the identification of these species with 83.9% accuracy. Hence, for their unambiguous identification, genetic screening is needed. A. marinus has seldom been documented, and when recorded, it has always been found in sites with clear marine influence. It is possible that only A. marinus preserves a life cycle related to the sea akin to the hypothesized ancestral galaxiid. We did not find evidence of claimed diadromy in A. taeniatus or A. zebra, and, therefore, these should be regarded as freshwater species. Finally, a lack of phylogeographic patterns and overrepresentation of uncommon haplotypes suggested demographic expansions in recent evolutionary time, especially of A. zebra, in line with the hypothesis of large-scale range expansion and lineage spread in western Patagonia.

New metrics for comparison of taxonomies reveal striking discrepancies among species delimitation methods in Madascincus lizards

Delimiting and describing species is fundamental to numerous biological disciplines such as evolution, macroecology, and conservation. Delimiting species as independent evolutionary lineages may and often does yield different outcomes depending on the species criteria applied, but methods should be chosen that minimize the inference of objectively erroneous species limits. Several protocols exploit single-gene or multi-gene coalescence statistics, assignment tests or other rationales related to nuclear DNA (nDNA) allele sharing to automatically delimit species. We apply seven different species delimitation protocols to a taxonomically confusing group of Malagasy lizards (Madascincus), and compare the resulting taxonomies with two newly developed metrics: the Taxonomic index of congruence C tax which quantifies the congruence between two taxonomies, and the Relative taxonomic resolving power index R tax which quantifies the potential of an approach to capture a high number of species boundaries. The protocols differed in the total number of species proposed, between 9 and 34, and were also highly incongruent in placing species boundaries. The Generalized Mixed Yule-Coalescent approach captured the highest number of potential species boundaries but many of these were clearly contradicted by extensive nDNA admixture between sympatric mitochondrial DNA (mtDNA) haplotype lineages. Delimiting species as phenotypically diagnosable mtDNA clades failed to detect two cryptic species that are unambiguous due to a lack of nDNA gene flow despite sympatry. We also consider the high number of species boundaries and their placement by multi-gene Bayesian species delimitation as poorly reliable whereas the Bayesian assignment test approach provided a species delimitation highly congruent with integrative taxonomic practice. The present study illustrates the trade-off in taxonomy between reliability (favored by conservative approaches) and resolving power (favored by inflationist approaches). Quantifying excessive splitting is more difficult than quantifying excessive lumping, suggesting a priority for conservative taxonomies in which errors are more liable to be detected and corrected by subsequent studies.

Phylogenetic systematics of Schacontia Dyar with descriptions of eight new species (Lepidoptera, Crambidae)

The Neotropical genus SchacontiaDyar (1914) is reviewed and revised to include eleven species. Schacontia replica Dyar, 1914, syn. n. and Schacontia pfeifferi Amsel, 1956, syn. n. are synonymized with Schacontia chanesalis (Druce, 1899) and eight new species are described: Schacontia umbra,sp. n., Schacontia speciosa,sp. n., Schacontia themis, sp. n., Schacontia rasa, sp. n., Schacontia nyx,sp. n., Schacontia clotho, sp. n., Schacontia lachesis, sp. n., and Schacontia atropos, sp. n. Three species, Schacontia medalba, Schacontia chanesalis, and Schacontia ysticalis, are re-described. An analysis of 64 characters (56 binary, 8 multistate; 5 head, 13 thoracic, 13 abdominal, 25 male genitalic, and 8 female genitalic) scored for all Schacontia and three outgroup species (Eustixia pupula Hübner, 1823, Glaphyria sesquistrialis Hübner, 1823, and Hellula undalis (Fabricius, 1781)) retrieved 8 equally most parsimonious trees (L=102, CI=71, RI=84) of which the strict consensus is: [[[[medalba + umbra] + chanesalis] + speciosa] + [ysticalis + [rasa + themis + [atropos + lachesis + nyx + clotho]]]]. The relevance of male secondary sexual characters to the diagnosis of Schacontia species is discussed.

Algal taxonomy: a road to nowhere?

The widespread view of taxonomy as an essentially retrogressive and outmoded science unable to cope with the current biodiversity crisis stimulated us to analyze the current status of cataloguing global algal diversity. Contrary to this largely pessimistic belief, species description rates of algae through time and trends in the number of active taxonomists, as revealed by the web resource AlgaeBase, show a much more positive picture. More species than ever before are being described by a large community of algal taxonomists. The lack of any decline in the rate at which new species and genera are described, however, is indicative of the large proportion of undiscovered diversity and bears heavily on any prediction of global algal species diversity and the time needed to catalogue it. The saturation of accumulation curves of higher taxa (family, order, and classes) on the other hand suggest that at these taxonomic levels most diversity has been discovered. This reasonably positive picture does not imply that algal taxonomy does not face serious challenges in the near future. The observed levels of cryptic diversity in algae, combined with the shift in methods used to characterize them, have resulted in a rampant uncertainty about the status of many older species. As a consequence, there is a tendency in phycology to move gradually away from traditional names to a more informal system whereby clade-, specimen- or strain-based identifiers are used to communicate biological information. Whether these informal names for species-level clades represent a temporary situation stimulated by the lag between species discovery and formal description, or an incipient alternative or parallel taxonomy, will be largely determined by how well we manage to integrate historical collections into modern taxonomic research. Additionally, there is a pressing need for a consensus about the organizational framework to manage the information about algal species names. An eventual strategy should preferably come out of an international working group that includes the various databases as well as the various phycological societies. In this strategy, phycologists should link up to major international initiatives that are currently being developed, such as the compulsory registration of taxonomic and nomenclatural acts and the introduction of Life Science Identifiers.

Intertwined arbovirus transmission activity: reassessing the transmission cycle paradigm

Arboviruses are emerging/reemerging infectious agents worldwide. The factors within this scenario include vector and host population fluctuations, climatic changes, anthropogenic activities that disturb ecosystems, an increase in international flights, human mobility, and genetic mutations that allow spill-over phenomenon. Arboviruses are maintained by biologic transmission among vectors and hosts. Sometimes this biological transmission is specific and includes one vector and host species such as Chikungunya (CHIKV), Dengue (DENV), and urban Yellow Fever (YFV). However, most of the arboviruses are generalist and they use many vectors and hosts species. From this perspective, arboviruses are maintained through a transmission network rather than a transmission cycle. This allows us to understand the complexity and dynamics of the transmission and maintenance of arboviruses in the ecosystems. The old perspective that arboviruses are maintained in close and stable transmission cycles should be modified by a new more integrative and dynamic idea, representing the real scenario where biological interactions have a much broader representation, indicating the constant adaptability of the biological entities.

DNA barcoding applied to ex situ tropical amphibian conservation programme reveals cryptic diversity in captive populations

Amphibians constitute a diverse yet still incompletely characterized clade of vertebrates, in which new species are still being discovered and described at a high rate. Amphibians are also increasingly endangered, due in part to disease-driven threats of extinctions. As an emergency response, conservationists have begun ex situ assurance colonies for priority species. The abundance of cryptic amphibian diversity, however, may cause problems for ex situ conservation. In this study we used a DNA barcoding approach to survey mitochondrial DNA (mtDNA) variation in captive populations of 10 species of Neotropical amphibians maintained in an ex situ assurance programme at El Valle Amphibian Conservation Center (EVACC) in the Republic of Panama. We combined these mtDNA sequences with genetic data from presumably conspecific wild populations sampled from across Panama, and applied genetic distance-based and character-based analyses to identify cryptic lineages. We found that three of ten species harboured substantial cryptic genetic diversity within EVACC, and an additional three species harboured cryptic diversity among wild populations, but not in captivity. Ex situ conservation efforts focused on amphibians are therefore vulnerable to an incomplete taxonomy leading to misidentification among cryptic species. DNA barcoding may therefore provide a simple, standardized protocol to identify cryptic diversity readily applicable to any amphibian community.

The DNA barcoding and the caveats with respect to its application to some species of Palaemonidae (Crustacea, Decapoda)

DNA-barcoding has recently attracted considerable attention due to its potential utility in aiding in species identification and discovery through the use of a short standardized sequence of mitochondrial DNA. Nevertheless, despite the fact that this technology has been proven a useful tool in several animal taxa, it also demonstrated limitations that may hinder correct application. Thus, its validity needs to be empirically evaluated in each taxonomic category before forward implementation. As the use of DNA barcoding within Palaemonidae may be of special interest, given its great interspecific morphological conservatism associated with considerable intraspecific morphological variation, we analyze here the potential of this technology in distinguishing and recovering some taxonomic boundaries within this family. We asked whether two GenBank-retrieved sets of COI sequences encompassing the conventional Barcode and Jerry-Pat regions possess the desired properties of reciprocal monophyly among species, and existence of a barcoding gap between intra- and interspecific variations, after performing a careful analysis of numt (nuclear mitochondrial DNA) contamination. These analyses revealed nine non-monophyletic species, with some cases of divergent intraspecific sequences, contrasted with interspecific similarity attained in others. Moreover, we were unable to identify any barcoding gap between intraspecific and interspecific divergences within Palaemonidae, although a threshold of 0.18 substitutions per site would differentiate intraspecific and congeneric divergences in 95% of the cases for the barcoding region. A fraction of the overlap could be certainly attributed to artifacts related to poor taxonomy, but even from this perspective DNA barcoding studies may help to uncover previously disregarded taxonomic and evolutionary issues.

DNA extraction from museum specimens of parasitic Hymenoptera

At the same time that molecular researchers are improving techniques to extract DNA from museum specimens, this increased demand for access to museum specimens has created tension between the need to preserve specimens for maintaining collections and morphological research and the desire to conduct molecular analyses. To address these concerns, we examined the suitability of non-invasive DNA extraction techniques on three species of parasitic Hymenoptera (Braconidae), and test the effects of body size (parasitoid species), age (time since collection), and DNA concentration from each extract on the probability of amplifying meaningful fragments of two commonly used genetic loci. We found that age was a significant factor for determining the probability of success for sequencing both 28S and COI fragments. While the size of the braconid parasitoids significantly affected the total amount of extracted DNA, neither size nor DNA concentration were significant factors for the amplification of either gene region. We also tested several primer combinations of various lengths, but were unable to amplify fragments longer than ∼150 base pairs. These short fragments of 28S and COI were however sufficient for species identification, and for the discovery of within species genetic variation.

Monophyly, distance and character-based multigene barcoding reveal extraordinary cryptic diversity in Nassarius: a complex and dangerous community

BACKGROUND

Correct identification and cryptic biodiversity revelation for marine organisms are pressing since the marine life is important in maintaining the balance of ecological system and is facing the problem of biodiversity crisis or food safety. DNA barcoding has been proved successful to provide resolution beyond the boundaries of morphological information. Nassarius, the common mudsnail, plays an important role in marine environment and has problem in food safety, but the classification of it is quite confused because of the complex morphological diversity.

METHODOLOGY/PRINCIPAL FINDINGS

Here we report a comprehensive barcoding analysis of 22 Nassarius species. We integrated the mitochondrial and nuclear sequences and the morphological characters to determine 13 Nassarius species studied and reveal four cryptic species and one pair synonyms. Distance, monophyly, and character-based barcoding methods were employed.

CONCLUSIONS/SIGNIFICANCE

Such successful identification and unexpected cryptic discovery is significant for Nassarius in food safety and species conversation and remind us to pay more attention to the hidden cryptic biodiversity ignored in marine life. Distance, monophyly, and character-based barcoding methods are all very helpful in identification but the character-based method shows some advantages.

Bioinformatic challenges for DNA metabarcoding of plants and animals

Almost all empirical studies in ecology have to identify the species involved in the ecological process under examination. DNA metabarcoding, which couples the principles of DNA barcoding with next generation sequencing technology, provides an opportunity to easily produce large amounts of data on biodiversity. Microbiologists have long used metabarcoding approaches, but use of this technique in the assessment of biodiversity in plant and animal communities is under-explored. Despite its relationship with DNA barcoding, several unique features of DNA metabarcoding justify the development of specific data analysis methodologies. In this review, we describe the bioinformatics tools available for DNA metabarcoding of plants and animals, and we revisit others developed for DNA barcoding or microbial metabarcoding. We also discuss the principles and associated tools for evaluating and comparing DNA barcodes in the context of DNA metabarcoding, for designing new custom-made barcodes adapted to specific ecological question, for dealing with PCR and sequencing errors, and for inferring taxonomical data from sequences.

MOLECULAR PHYLOGENY OF THE GENUS KUMANOA (BATRACHOSPERMALES, RHODOPHYTA)(1)

Species belonging to the newly established genus Kumanoa were sampled from locations worldwide. DNA sequence data from the rbcL gene, cox1 barcode region, and universal plastid amplicon (UPA) were collected. The new sequence data for the rbcL were combined with the extensive batrachospermalean rbcL data available in GenBank. Single gene rbcL results showed the genus Kumanoa to be a well-supported clade, and there was high statistical support for many of the terminal nodes. However, with this gene alone, there was very little support for any of the internal nodes. Analysis of the concatenated data set (rbcL, cox1, and UPA) provided higher statistical support across the tree. The taxa K. vittata and K. amazonensis formed a basal grade, and both were on relatively long branches. Three new species are proposed, K. holtonii, K. gudjewga, and K. novaecaledonensis; K. procarpa var. americana is raised to species level. In addition, the synonymy of K. capensis and K. breviarticulata is proposed, with K. capensis having precedence. Five new combinations are made, bringing the total number of accepted species in Kumanoa to 31. The phylogenetic analyses did not reveal any interpretable biogeographic patterns within the genus (e.g., K. spermatiophora from the tropical oceanic island Maui, Hawaii, was sister to K. faroensis from temperate midcontinental Ohio in North America). Previously hypothesized relationships among groups of species were not substantiated in the phylogenetic analyses, and no intrageneric classification is recommended based on current knowledge.

Integrative taxonomy for continental-scale terrestrial insect observations

Although 21^st century ecology uses unprecedented technology at the largest spatio-temporal scales in history, the data remain reliant on sound taxonomic practices that derive from 18^th century science. The importance of accurate species identifications has been assessed repeatedly and in instances where inappropriate assignments have been made there have been costly consequences. The National Ecological Observatory Network (NEON) will use a standardized system based upon an integrative taxonomic foundation to conduct observations of the focal terrestrial insect taxa, ground beetles and mosquitoes, at the continental scale for a 30 year monitoring program. The use of molecular data for continental-scale, multi-decadal research conducted by a geographically widely distributed set of researchers has not been evaluated until this point. The current paper addresses the development of a reference library for verifying species identifications at NEON and the key ways in which this resource will enhance a variety of user communities.

Assessment of three mitochondrial genes (16S, Cytb, CO1) for identifying species in the Praomyini tribe (Rodentia: Muridae)

The Praomyini tribe is one of the most diverse and abundant groups of Old World rodents. Several species are known to be involved in crop damage and in the epidemiology of several human and cattle diseases. Due to the existence of sibling species their identification is often problematic. Thus an easy, fast and accurate species identification tool is needed for non-systematicians to correctly identify Praomyini species. In this study we compare the usefulness of three genes (16S, Cytb, CO1) for identifying species of this tribe. A total of 426 specimens representing 40 species (sampled across their geographical range) were sequenced for the three genes. Nearly all of the species included in our study are monophyletic in the neighbour joining trees. The degree of intra-specific variability tends to be lower than the divergence between species, but no barcoding gap is detected. The success rate of the statistical methods of species identification is excellent (up to 99% or 100% for statistical supervised classification methods as the k-Nearest Neighbour or Random Forest). The 16S gene is 2.5 less variable than the Cytb and CO1 genes. As a result its discriminatory power is smaller. To sum up, our results suggest that using DNA markers for identifying species in the Praomyini tribe is a largely valid approach, and that the CO1 and Cytb genes are better DNA markers than the 16S gene. Our results confirm the usefulness of statistical methods such as the Random Forest and the 1-NN methods to assign a sequence to a species, even when the number of species is relatively large. Based on our NJ trees and the distribution of all intraspecific and interspecific pairwise nucleotide distances, we highlight the presence of several potentially new species within the Praomyini tribe that should be subject to corroboration assessments.

Large-scale species delimitation method for hyperdiverse groups

Accelerating the description of biodiversity is a major challenge as extinction rates increase. Integrative taxonomy combining molecular, morphological, ecological and geographical data is seen as the best route to reliably identify species. Classic molluscan taxonomic methodology proposes primary species hypotheses (PSHs) based on shell morphology. However, in hyperdiverse groups, such as the molluscan family Turridae, where most of the species remain unknown and for which homoplasy and plasticity of morphological characters is common, shell-based PSHs can be arduous. A four-pronged approach was employed to generate robust species hypotheses of a 1000 specimen South-West Pacific Turridae data set in which: (i) analysis of COI DNA Barcode gene is coupled with (ii) species delimitation tools GMYC (General Mixed Yule Coalescence Method) and ABGD (Automatic Barcode Gap Discovery) to propose PSHs that are then (iii) visualized using Klee diagrams and (iv) evaluated with additional evidence, such as nuclear gene rRNA 28S, morphological characters, geographical and bathymetrical distribution to determine conclusive secondary species hypotheses (SSHs). The integrative taxonomy approach applied identified 87 Turridae species, more than doubling the amount previously known in the Gemmula genus. In contrast to a predominantly shell-based morphological approach, which over the last 30 years proposed only 13 new species names for the Turridae genus Gemmula, the integrative approach described here identified 27 novel species hypotheses not linked to available species names in the literature. The formalized strategy applied here outlines an effective and reproducible protocol for large-scale species delimitation of hyperdiverse groups.

First large-scale DNA barcoding assessment of reptiles in the biodiversity hotspot of Madagascar, based on newly designed COI primers

BACKGROUND

DNA barcoding of non-avian reptiles based on the cytochrome oxidase subunit I (COI) gene is still in a very early stage, mainly due to technical problems. Using a newly developed set of reptile-specific primers for COI we present the first comprehensive study targeting the entire reptile fauna of the fourth-largest island in the world, the biodiversity hotspot of Madagascar.

METHODOLOGY/PRINCIPAL FINDINGS

Representatives of the majority of Madagascan non-avian reptile species (including Squamata and Testudines) were sampled and successfully DNA barcoded. The new primer pair achieved a constantly high success rate (72.7-100%) for most squamates. More than 250 species of reptiles (out of the 393 described ones; representing around 64% of the known diversity of species) were barcoded. The average interspecific genetic distance within families ranged from a low of 13.4% in the Boidae to a high of 29.8% in the Gekkonidae. Using the average genetic divergence between sister species as a threshold, 41-48 new candidate (undescribed) species were identified. Simulations were used to evaluate the performance of DNA barcoding as a function of completeness of taxon sampling and fragment length. Compared with available multi-gene phylogenies, DNA barcoding correctly assigned most samples to species, genus and family with high confidence and the analysis of fewer taxa resulted in an increased number of well supported lineages. Shorter marker-lengths generally decreased the number of well supported nodes, but even mini-barcodes of 100 bp correctly assigned many samples to genus and family.

CONCLUSIONS/SIGNIFICANCE

The new protocols might help to promote DNA barcoding of reptiles and the established library of reference DNA barcodes will facilitate the molecular identification of Madagascan reptiles. Our results might be useful to easily recognize undescribed diversity (i.e. novel taxa), to resolve taxonomic problems, and to monitor the international pet trade without specialized expert knowledge.

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.

DNA barcoding of recently diverged species: relative performance of matching methods

Recently diverged species are challenging for identification, yet they are frequently of special interest scientifically as well as from a regulatory perspective. DNA barcoding has proven instrumental in species identification, especially in insects and vertebrates, but for the identification of recently diverged species it has been reported to be problematic in some cases. Problems are mostly due to incomplete lineage sorting or simply lack of a 'barcode gap' and probably related to large effective population size and/or low mutation rate. Our objective was to compare six methods in their ability to correctly identify recently diverged species with DNA barcodes: neighbor joining and parsimony (both tree-based), nearest neighbor and BLAST (similarity-based), and the diagnostic methods DNA-BAR, and BLOG. We analyzed simulated data assuming three different effective population sizes as well as three selected empirical data sets from published studies. Results show, as expected, that success rates are significantly lower for recently diverged species (∼75%) than for older species (∼97%) (P<0.00001). Similarity-based and diagnostic methods significantly outperform tree-based methods, when applied to simulated DNA barcode data (P<0.00001). The diagnostic method BLOG had highest correct query identification rate based on simulated (86.2%) as well as empirical data (93.1%), indicating that it is a consistently better method overall. Another advantage of BLOG is that it offers species-level information that can be used outside the realm of DNA barcoding, for instance in species description or molecular detection assays. Even though we can confirm that identification success based on DNA barcoding is generally high in our data, recently diverged species remain difficult to identify. Nevertheless, our results contribute to improved solutions for their accurate identification.

Development of a DNA barcoding system for seagrasses: successful but not simple

Seagrasses, a unique group of submerged flowering plants, profoundly influence the physical, chemical and biological environments of coastal waters through their high primary productivity and nutrient recycling ability. They provide habitat for aquatic life, alter water flow, stabilize the ground and mitigate the impact of nutrient pollution. at the coast region. Although on a global scale seagrasses represent less than 0.1% of the angiosperm taxa, the taxonomical ambiguity in delineating seagrass species is high. Thus, the taxonomy of several genera is unsolved. While seagrasses are capable of performing both, sexual and asexual reproduction, vegetative reproduction is common and sexual progenies are always short lived and epimeral in nature. This makes species differentiation often difficult, especially for non-taxonomists since the flower as a distinct morphological trait is missing. Our goal is to develop a DNA barcoding system assisting also non-taxonomists to identify regional seagrass species. The results will be corroborated by publicly available sequence data. The main focus is on the 14 described seagrass species of India, supplemented with seagrasses from temperate regions. According to the recommendations of the Consortium for the Barcoding of Life (CBOL) rbcL and matK were used in this study. After optimization of the DNA extraction method from preserved seagrass material, the respective sequences were amplified from all species analyzed. Tree- and character-based approaches demonstrate that the rbcL sequence fragment is capable of resolving up to family and genus level. Only matK sequences were reliable in resolving species and partially the ecotype level. Additionally, a plastidic gene spacer was included in the analysis to confirm the identification level. Although the analysis of these three loci solved several nodes, a few complexes remained unsolved, even when constructing a combined tree for all three loci. Our approaches contribute to the understanding of the morphological plasticity of seagrasses versus genetic differentiation.

Molecular and phenotypic evidence of a new species of genus Esox (Esocidae, Esociformes, Actinopterygii): the southern pike, Esox flaviae

We address the taxonomic position of the southern European individuals of pike, performing a series of tests and comparisons from morphology, DNA taxonomy and population genetics parameters, in order to support the hypothesis that two species of pike, and not only one, exist in Europe. A strong relationship emerged between a northern genotype supported by COI, Cytb, AFLP and specific fragments, and a phenotype with round spot skin colour pattern and a large number of scales in the lateral line, clearly separated from a southern genotype with other skin colour pattern and a low number of scales in the lateral line. DNA taxonomy, based on a coalescent approach (GMYC) from phylogenetic reconstructions on COI and Cytb together with AFLP admixture analysis, supported the existence of two independently evolving entities. Such differences are not simply due to geographic distances, as northern European samples are more similar to Canadian and Chinese samples than the southern Europe ones. Thus, given that the differences between the two groups of European pike are significant at the phenotypic, genotypic and geographical levels, we propose the identification of two pike species: the already known northern pike (Esox lucius) and the southern pike (E. flaviae n.sp.). The correct identification of these two lineages as independent species should give rise to a ban on the introduction of northern pikes in southern Europe for recreational fishing, due to potential problems of hybridisation.

High levels of cryptic species diversity uncovered in Amazonian frogs

One of the greatest challenges for biodiversity conservation is the poor understanding of species diversity. Molecular methods have dramatically improved our ability to uncover cryptic species, but the magnitude of cryptic diversity remains unknown, particularly in diverse tropical regions such as the Amazon Basin. Uncovering cryptic diversity in amphibians is particularly pressing because amphibians are going extinct globally at an alarming rate. Here, we use an integrative analysis of two independent Amazonian frog clades, Engystomops toadlets and Hypsiboas treefrogs, to test whether species richness is underestimated and, if so, by how much. We sampled intensively in six countries with a focus in Ecuador (Engystomops: 252 individuals from 36 localities; Hypsiboas: 208 individuals from 65 localities) and combined mitochondrial DNA, nuclear DNA, morphological, and bioacoustic data to detect cryptic species. We found that in both clades, species richness was severely underestimated, with more undescribed species than described species. In Engystomops, the two currently recognized species are actually five to seven species (a 150-250% increase in species richness); in Hypsiboas, two recognized species represent six to nine species (a 200-350% increase). Our results suggest that Amazonian frog biodiversity is much more severely underestimated than previously thought.