DNA barcodes from century-old type specimens using next-generation sequencing

DNA barcodes from over-a-century-old type specimens shed light on the taxonomy of a group of rare butterflies (Lepidoptera: Nymphalidae: Calinaginae)

We analyzed COI barcode sequences from 138 over-a-century old specimens of Calinaga including 36 name-bearing type specimens stored at the Natural History Museum London. These new data, combined with previously available RPS5 sequences, divide the Calinaga samples into four well-supported mitochondrial lineages that together with a novel wing-pattern analysis, support the recognition of six species (lhatso, buddha, brahma, aborica, formosana and davidis), with all other names subsumed either as subspecies or synonyms. One new taxon is described, Calinaga aborica naima Vane-Wright, ssp. n.

An annotated catalogue of selected historical type specimens, including genetic data, housed in the Natural History Museum Vienna

Museum collections are an important source for resolving taxonomic issues and species delimitation. Type specimens as name-bearing specimens, traditionally used in morphology-based taxonomy, are, due to the progress in historical DNA methodology, increasingly used in molecular taxonomic studies. Museum collections are subject to constant deterioration and major disasters. The digitisation of collections offers a partial solution to these problems and makes museum collections more accessible to the wider scientific community. The Extended Specimen Approach (ESA) is a method of digitisation that goes beyond the physical specimen to include the historical information stored in the collection. The collections of the Natural History Museum Vienna represent one of the largest non-university research centres in Europe and, due to their size and numerous type specimens, are frequently used for taxonomic studies by visiting and resident scientists. Recently, a version of ESA was presented in the common catalogue of the Fish and Evertebrata Varia collections and extended to include genetic information on type specimens in a case study of a torpedo ray. Here the case study was extended to a heterogeneous selection of historical type series from different collections with the type locality of Vienna. The goal was to apply the ESA, including genetic data on a selected set of type material: three parasitic worms, three myriapods, two insects, twelve fishes, and one bird species. Five hundred digital items (photographs, X-rays, scans) were produced, and genetic analysis was successful in eleven of the 21 type series. In one case a complete mitochondrial genome was assembled, and in another case ten short fragments (100-230 bp) of the cytochrome oxidase I gene were amplified and sequenced. For five type series, genetic analysis confirmed their taxonomic status as previously recognised synonyms, and for one the analysis supported its status as a distinct species. For two species, genetic information was provided for the first time. This catalogue thus demonstrates the usefulness of ESA in providing digitised data of types that can be easily made available to scientists worldwide for further study.

A genetic atlas for the butterflies of continental Canada and United States

Multi-locus genetic data for phylogeographic studies is generally limited in geographic and taxonomic scope as most studies only examine a few related species. The strong adoption of DNA barcoding has generated large datasets of mtDNA COI sequences. This work examines the butterfly fauna of Canada and United States based on 13,236 COI barcode records derived from 619 species. It compiles i) geographic maps depicting the spatial distribution of haplotypes, ii) haplotype networks (minimum spanning trees), and iii) standard indices of genetic diversity such as nucleotide diversity (π), haplotype richness (H), and a measure of spatial genetic structure (GST). High intraspecific genetic diversity and marked spatial structure were observed in the northwestern and southern North America, as well as in proximity to mountain chains. While species generally displayed concordance between genetic diversity and spatial structure, some revealed incongruence between these two metrics. Interestingly, most species falling in this category shared their barcode sequences with one at least other species. Aside from revealing large-scale phylogeographic patterns and shedding light on the processes underlying these patterns, this work also exposed cases of potential synonymy and hybridization.

Surprising discovery of an enigmatic geometrid in Croatia: Mirlatiaarcuata, gen. nov., sp. nov. (Lepidoptera, Geometridae)

A new monotypic genus of Geometridae, Mirlatiagen. nov., and a new species, M.arcuatasp. nov., are described from Croatia. Based on external and genitalia characters, the new genus is tentatively placed in the subfamily Larentiinae. However, the new genus takes a highly isolated position by having unique characters of the tympanum and showing an unusually long pectination of female antennae. Genetic analysis of a fragmented DNA barcode (mtDNA; cytochrome c oxidase 1) did not result in a clear assignation to any geometrid subfamily or tribe. Adults, male and female genitalia, and habitat photos of the type locality of the new species are illustrated.

Developing the Protocol Infrastructure for DNA Sequencing Natural History Collections

Intentionally preserved biological material in natural history collections represents a vast repository of biodiversity. Advances in laboratory and sequencing technologies have made these specimens increasingly accessible for genomic analyses, offering a window into the genetic past of species and often permitting access to information that can no longer be sampled in the wild. Due to their age, preparation and storage conditions, DNA retrieved from museum and herbarium specimens is often poor in yield, heavily fragmented and biochemically modified. This not only poses methodological challenges in recovering nucleotide sequences, but also makes such investigations susceptible to environmental and laboratory contamination. In this paper, we review the practical challenges associated with making the recovery of DNA sequence data from museum collections more routine. We first review key operational principles and issues to address, to guide the decision-making process and dialogue between researchers and curators about when and how to sample museum specimens for genomic analyses. We then outline the range of steps that can be taken to reduce the likelihood of contamination including laboratory set-ups, workflows and working practices. We finish by presenting a series of case studies, each focusing on protocol practicalities for the application of different mainstream methodologies to museum specimens including: (i) shotgun sequencing of insect mitogenomes, (ii) whole genome sequencing of insects, (iii) genome skimming to recover plant plastid genomes from herbarium specimens, (iv) target capture of multi-locus nuclear sequences from herbarium specimens, (v) RAD-sequencing of bird specimens and (vi) shotgun sequencing of ancient bovid bone samples.

Systematics and integrative taxonomic revision of the tribe Scopulini Duponchel, 1845 in Iran (Lepidoptera: Geometridae: Sterrhinae)

The Iranian taxa of the tribe Scopulini are taxonomically revised. The systematic positions of the genera Cinglis Guene, 1858, Glossotrophia Prout, 1913, Pseudocinglis Hausmann, 1994 and Scopuloides Hausmann, 1994, with uncertain validity and/or position within the tribe Scopulini Duponchel, 1845 (Lepidoptera: Sterrhinae), are further elucidated by use of one mitochondrial and up to nine protein-coding nuclear gene regions. Available type specimens of the described species and more than 2,600 additional specimens were morphologically investigated. In addition, over 400 genitalia preparations were made and examined together with distribution data and DNA barcodes. As a result of the multi-gene analysis, the genera Cinglis stat. rev. and Scopuloides stat. rev. are re-validated at the genus level. The genus Pseudocinglis syn. nov. is regarded as a junior synonym of the genus Cinglis stat. rev. and Glossotrophia syn. nov. is regarded as a junior synonym of the genus Scopula. Cinglis eurata (Prout, 1913) comb. nov. and Cinglis benigna (Brandt, 1941) comb. nov. are combined with the genus Cinglis. Additionally, Cinglis benigna amseli (Wiltshire, 1967) syn. nov. is regarded as a synonym of C. benigna. Scopula adulteraria (Erschov, 1874) stat. nov. is raised from subspecies to species rank; Scopula iranaria Bytinski-Salz & Brandt, 1937 syn. nov. is synonymized with S. flaccidaria (Zeller, 1852); S. transcaspica taftanica Brandt, 1941 syn. nov. is synonymized with S. transcaspica Prout, 1935; S. diffinaria asiatica (Brandt, 1938) syn. nov. is synonymized with S. diffinaria (Prout, 1913) and Glossotrophia bullata Vojnits, 1986 syn. nov. is synonymized with Scopula sacraria ariana (Ebert, 1965). The female genitalia of Scopula lactarioides Brandt, 1941 are described and illustrated for the first time. In total, the presence of 33 species of Scopulini in Iran is confirmed. Wing patterns, male and female genitalia and diagnostic characters of most Iranian Scopulini species are depicted and their distribution ranges are mapped.

Molecular Barcoding: A Tool to Guarantee Correct Seafood Labelling and Quality and Preserve the Conservation of Endangered Species

The recent increase in international fish trade leads to the need for improving the traceability of fishery products. In relation to this, consistent monitoring of the production chain focusing on technological developments, handling, processing and distribution via global networks is necessary. Molecular barcoding has therefore been suggested as the gold standard in seafood species traceability and labelling. This review describes the DNA barcoding methodology for preventing food fraud and adulteration in fish. In particular, attention has been focused on the application of molecular techniques to determine the identity and authenticity of fish products, to discriminate the presence of different species in processed seafood and to characterize raw materials undergoing food industry processes. In this regard, we herein present a large number of studies performed in different countries, showing the most reliable DNA barcodes for species identification based on both mitochondrial (COI, cytb, 16S rDNA and 12S rDNA) and nuclear genes. Results are discussed considering the advantages and disadvantages of the different techniques in relation to different scientific issues. Special regard has been dedicated to a dual approach referring to both the consumer's health and the conservation of threatened species, with a special focus on the feasibility of the different genetic and genomic approaches in relation to both scientific objectives and permissible costs to obtain reliable traceability.

Interrogating 1000 insect genomes for NUMTs: A risk assessment for estimates of species richness

The nuclear genomes of most animal species include NUMTs, segments of the mitogenome incorporated into their chromosomes. Although NUMT counts are known to vary greatly among species, there has been no comprehensive study of their frequency/attributes in the most diverse group of terrestrial organisms, insects. This study examines NUMTs derived from a 658 bp 5' segment of the cytochrome c oxidase I (COI) gene, the barcode region for the animal kingdom. This assessment is important because unrecognized NUMTs can elevate estimates of species richness obtained through DNA barcoding and derived approaches (eDNA, metabarcoding). This investigation detected nearly 10,000 COI NUMTs ≥ 100 bp in the genomes of 1,002 insect species (range = 0-443). Variation in nuclear genome size explained 56% of the mitogenome-wide variation in NUMT counts. Although insect orders with the largest genome sizes possessed the highest NUMT counts, there was considerable variation among their component lineages. Two thirds of COI NUMTs possessed an IPSC (indel and/or premature stop codon) allowing their recognition and exclusion from downstream analyses. The remainder can elevate species richness as they showed 10.1% mean divergence from their mitochondrial homologue. The extent of exposure to "ghost species" is strongly impacted by the target amplicon's length. NUMTs can raise apparent species richness by up to 22% when a 658 bp COI amplicon is examined versus a doubling of apparent richness when 150 bp amplicons are targeted. Given these impacts, metabarcoding and eDNA studies should target the longest possible amplicons while also avoiding use of 12S/16S rDNA as they triple NUMT exposure because IPSC screens cannot be employed.

A workflow for expanding DNA barcode reference libraries through 'museum harvesting' of natural history collections

Natural history collections are the physical repositories of our knowledge on species, the entities of biodiversity. Making this knowledge accessible to society - through, for example, digitisation or the construction of a validated, global DNA barcode library - is of crucial importance. To this end, we developed and streamlined a workflow for 'museum harvesting' of authoritatively identified Diptera specimens from the Smithsonian Institution's National Museum of Natural History. Our detailed workflow includes both on-site and off-site processing through specimen selection, labelling, imaging, tissue sampling, databasing and DNA barcoding. This approach was tested by harvesting and DNA barcoding 941 voucher specimens, representing 32 families, 819 genera and 695 identified species collected from 100 countries. We recovered 867 sequences (> 0 base pairs) with a sequencing success of 88.8% (727 of 819 sequenced genera gained a barcode > 300 base pairs). While Sanger-based methods were more effective for recently-collected specimens, the methods employing next-generation sequencing recovered barcodes for specimens over a century old. The utility of the newly-generated reference barcodes is demonstrated by the subsequent taxonomic assignment of nearly 5000 specimen records in the Barcode of Life Data Systems.

Enhancing DNA barcode reference libraries by harvesting terrestrial arthropods at the Smithsonian's National Museum of Natural History

The use of DNA barcoding has revolutionised biodiversity science, but its application depends on the existence of comprehensive and reliable reference libraries. For many poorly known taxa, such reference sequences are missing even at higher-level taxonomic scales. We harvested the collections of the Smithsonian's National Museum of Natural History (USNM) to generate DNA barcoding sequences for genera of terrestrial arthropods previously not recorded in one or more major public sequence databases. Our workflow used a mix of Sanger and Next-Generation Sequencing (NGS) approaches to maximise sequence recovery while ensuring affordable cost. In total, COI sequences were obtained for 5,686 specimens belonging to 3,737 determined species in 3,886 genera and 205 families distributed in 137 countries. Success rates varied widely according to collection data and focal taxon. NGS helped recover sequences of specimens that failed a previous run of Sanger sequencing. Success rates and the optimal balance between Sanger and NGS are the most important drivers to maximise output and minimise cost in future projects. The corresponding sequence and taxonomic data can be accessed through the Barcode of Life Data System, GenBank, the Global Biodiversity Information Facility, the Global Genome Biodiversity Network Data Portal and the NMNH data portal.

Molecular Weevil Identification Project: A thoroughly curated barcode release of 1300 Western Palearctic weevil species (Coleoptera, Curculionoidea)

The Molecular Weevil Identification project (MWI) studies the systematics of Western Palearctic weevils (superfamily Curculionoidea) in an integrative taxonomic approach of DNA barcoding, morphology and ecology. This barcode release provides almost 3600 curated CO1 sequences linked to morphological vouchers in about 1300 weevil species. The dataset is presented in statistical distance tables and as a Neighbour-Joining tree. Bayesian Inference trees are computed for the subfamilies Cryptorhynchinae, Apioninae and Ceutorhynchinae. Altogether, 18 unresolved taxonomic issues are discussed. A new barcode primer set is presented. Finally, we establish group-specific genetic distances for many weevil genera to serve as a tool in species delineation. These values are statistically based on distances between "good species" and their congeners. With this morphologically calibrated approach, we could resolve most alpha-taxonomic questions within the MWI project.

Using DNA metabarcoding to assess insect diversity in citrus orchards

Background

DNA metabarcoding is rapidly emerging as a cost-effective approach for large-scale biodiversity assessment and pest monitoring. The current study employed metabarcoding to assess insect diversity in citrus orchards in Ganzhou City, Jiangxi, China in both 2018 and 2019. Insects were sampled using Malaise traps deployed in three citrus orchards producing a total of 43 pooled monthly samples.

Methods

The Malaise trap samples were sequenced following DNA metabarcoding workflow. Generated sequences were curated and analyzed using two cloud databases and analytical platforms, the barcode of life data system (BOLD) and multiplex barcode research and visualization environment (mBRAVE).

Results

These platforms assigned the sequences to 2,141 barcode index numbers (BINs), a species proxy. Most (63%) of the BINs were shared among the three sampling sites while BIN sharing between any two sites did not exceed 71%. Shannon diversity index (H') showed a similar pattern of BIN assortment at the three sampling sites. Beta diversity analysis by Jaccard similarity coefficient (J) and Bray-Curtis distance matrix (BC) revealed a high level of BIN similarity among the three sites (J = 0.67-0.68; BC = 0.19-0.20). Comparison of BIN records against all those on BOLD made it possible to identify 40% of the BINs to a species, 57% to a genus, 97% to a family and 99% to an order. BINs which received a species match on BOLD were placed in one of four categories based on this assignment: pest, parasitoid, predator, or pollinator. As this study provides the first baseline data on insect biodiversity in Chinese citrus plantations, it is a valuable resource for research in a broad range of areas such as pest management and monitoring beneficial insects in citrus gardens.

Museomics and the holotype of a critically endangered cricetid rodent provide key evidence of an undescribed genus

Historical DNA obtained from voucher specimens housed in natural history museums worldwide have allowed the study of elusive, rare or even extinct species that in many cases are solely represented by museum holdings. This has resulted in the increase of taxonomic representation of many taxa, has led to the discovery of new species, and has yielded stunning novel insights into the evolutionary history of cryptic or even undescribed species. Peromyscus mekisturus, is a critically endangered cricetid rodent endemic to Mexico and is only known from two museum specimens collected in 1898 and 1947. Intensive field work efforts to attempt to determine if viable populations still exist have failed, suggesting that this species is extinct or is nearing extinction. In addition, a recent study using mitogenomes demonstrated that P. mekisturus forms a well-supported clade outside the genus Peromyscus and hypothesized that this taxon is the sister group of the genus Reithrodontomys. Here, we used target enrichment and high-throughput sequencing of several thousand nuclear ultraconserved elements and mitogenomes to reconstruct dated phylogenies to test the previous phylogenetic hypothesis. We analyzed the holotype and the only other known specimen of P. mekisturus and museum samples from other peromyscine rodents to test the phylogenetic position of the species. Our results confirm that the only two specimens known to science of P. mekisturus belong to the same species and support the hypothesis that this species belongs to an undescribed genus of cricetid rodents that is sister to the genus Reithrodontomys. We dated the origin of P. mekisturus together with other speciation events in peromyscines during the late Pliocene – early Pleistocene and related these events with the Pleistocene climatic cycles. In light of our results, we recommend a taxonomic re-evaluation of this enigmatic species to properly recognize its taxonomic status as a new genus. We also acknowledge the relevance of generating genomic data from type specimens and highlight the need and importance of continuing to build the scientific heritage of the collections to study and better understand past, present, and future biodiversity.

Message in a Bottle-Metabarcoding enables biodiversity comparisons across ecoregions

Background

Traditional biomonitoring approaches have delivered a basic understanding of biodiversity, but they cannot support the large-scale assessments required to manage and protect entire ecosystems. This study used DNA metabarcoding to assess spatial and temporal variation in species richness and diversity in arthropod communities from 52 protected areas spanning 3 Canadian ecoregions.

Results

This study revealed the presence of 26,263 arthropod species in the 3 ecoregions and indicated that at least another 3,000–5,000 await detection. Results further demonstrate that communities are more similar within than between ecoregions, even after controlling for geographical distance. Overall α-diversity declined from east to west, reflecting a gradient in habitat disturbance. Shifts in species composition were high at every site, with turnover greater than nestedness, suggesting the presence of many transient species.

Conclusions

Differences in species composition among their arthropod communities confirm that ecoregions are a useful synoptic for biogeographic patterns and for structuring conservation efforts. The present results also demonstrate that metabarcoding enables large-scale monitoring of shifts in species composition, making it possible to move beyond the biomass measurements that have been the key metric used in prior efforts to track change in arthropod communities.

Tracing the invasion of a leaf-mining moth in the Palearctic through DNA barcoding of historical herbaria

The lime leaf-miner, Phyllonorycter issikii is an invasive micromoth with an unusually higher number of haplotypes in the invaded area (Europe, Western Siberia) compared to its putative native region (East Asia). The origin of the genetic diversity in the neocolonized region remains unclear. We surveyed over 15 thousand herbarium specimens of lime trees (Tilia spp.) collected across the Palearctic over a period of 252 years (1764-2016) looking for preserved larvae within the archival leaf mines. We found 203 herbarium specimens with leaf mines of Ph. issikii collected in East Asia, one of them dating back to 1830, i.e. 133 years before the description of the species. In contrast, only 22 herbarium specimens collected in the West Palearctic in the last three decades (1987-2015) carried leaf mines. DNA barcoding of archival specimens revealed 32 haplotypes out of which 23 were novel (not known from modern populations) and found exclusively in East Asia. Six haplotypes are shared between both native and invaded areas and only two were responsible for the recent invasion of the Western Palearctic. The remarkable number of newly discovered haplotypes in archival populations supports East Asia as the native region and the source area of invasion.

Unearthing soil arthropod diversity through DNA metabarcoding

DNA metabarcoding has the potential to greatly advance understanding of soil biodiversity, but this approach has seen limited application for the most abundant and species-rich group of soil fauna-the arthropods. This study begins to address this gap by comparing information on species composition recovered from metabarcoding two types of bulk samples (specimens, soil) from a temperate zone site and from bulk soil samples collected at eight sites in the Arctic. Analysis of 22 samples (3 specimen, 19 soil) revealed 410 arthropod OTUs belonging to 112 families, 25 orders, and nine classes. Studies at the temperate zone site revealed little overlap in species composition between soil and specimen samples, but more overlap at higher taxonomic levels (families, orders) and congruent patterns of α- and β-diversity. Expansion of soil analyses to the Arctic revealed locally rich, highly dissimilar, and spatially structured assemblages compatible with dispersal limited and environmentally driven assembly. The current study demonstrates that DNA metabarcoding of bulk soil enables rapid, large-scale assessments of soil arthropod diversity. However, deep sequence coverage is required to adequately capture the species present in these samples, and expansion of the DNA barcode reference library is necessary to improve taxonomic resolution of the sequences recovered through this approach.

Scenopinusjerei, a new species of window fly (Diptera, Scenopinidae) from Finland

A new species of window fly (Diptera: Scenopinidae), Scenopinusjereisp. nov., with characteristic bicoloured legs and completely black halteres, is described from Finland. To exclude potential previously named species, a survey of the relevant type specimens as well as original descriptions of the Palearctic and Nearctic Scenopinus species has been conducted, including old Scenopinusfenestralis (Linnaeus) synonyms. Scenopinusjereisp. nov. is likely to be an overlooked, boreal forest specialist living in the nests of cavity-nesting birds. An identification key to the European species is provided.

A Minimally Morphologically Destructive Approach for DNA Retrieval and Whole-Genome Shotgun Sequencing of Pinned Historic Dipteran Vector Species

Museum collections contain enormous quantities of insect specimens collected over the past century, covering a period of increased and varied insecticide usage. These historic collections are therefore incredibly valuable as genomic snapshots of organisms before, during, and after exposure to novel selective pressures. However, these samples come with their own challenges compared with present-day collections, as they are fragile and retrievable DNA is low yield and fragmented. In this article, we tested several DNA extraction procedures across pinned historic Diptera specimens from four disease vector genera: Anopheles, Aedes, Culex, and Glossina. We identify an approach that minimizes morphological damage while maximizing DNA retrieval for Illumina library preparation and sequencing that can accommodate the fragmented and low yield nature of historic DNA. We identify several key points in retrieving sufficient DNA while keeping morphological damage to a minimum: an initial rehydration step, a short incubation without agitation in a modified low salt Proteinase K buffer (referred to as "lysis buffer C" throughout), and critical point drying of samples post-extraction to prevent tissue collapse caused by air drying. The suggested method presented here provides a solid foundation for exploring the genomes and morphology of historic Diptera collections.

A molecular-based identification resource for the arthropods of Finland

To associate specimens identified by molecular characters to other biological knowledge, we need reference sequences annotated by Linnaean taxonomy. In this study, we (1) report the creation of a comprehensive reference library of DNA barcodes for the arthropods of an entire country (Finland), (2) publish this library, and (3) deliver a new identification tool for insects and spiders, as based on this resource. The reference library contains mtDNA COI barcodes for 11,275 (43%) of 26,437 arthropod species known from Finland, including 10,811 (45%) of 23,956 insect species. To quantify the improvement in identification accuracy enabled by the current reference library, we ran 1000 Finnish insect and spider species through the Barcode of Life Data system (BOLD) identification engine. Of these, 91% were correctly assigned to a unique species when compared to the new reference library alone, 85% were correctly identified when compared to BOLD with the new material included, and 75% with the new material excluded. To capitalize on this resource, we used the new reference material to train a probabilistic taxonomic assignment tool, FinPROTAX, scoring high success. For the full-length barcode region, the accuracy of taxonomic assignments at the level of classes, orders, families, subfamilies, tribes, genera, and species reached 99.9%, 99.9%, 99.8%, 99.7%, 99.4%, 96.8%, and 88.5%, respectively. The FinBOL arthropod reference library and FinPROTAX are available through the Finnish Biodiversity Information Facility (www.laji.fi) at https://laji.fi/en/theme/protax. Overall, the FinBOL investment represents a massive capacity-transfer from the taxonomic community of Finland to all sectors of society.

Assessing DNA for fish identifications from reference collections: the good, bad and ugly shed light on formalin fixation and sequencing approaches

Natural history collections are repositories of biodiversity and are potentially used by molecular ecologists for comparative taxonomic, phylogenetic, biogeographic and forensic purposes. Specimens in fish collections are preserved using a combination of methods with many fixed in formalin and then preserved in ethanol for long-term storage. Formalin fixation damages DNA, thereby limiting genetic analyses. In this study, the authors compared the DNA barcoding and identification success for frozen and formalin-fixed tissues obtained from specimens in the CSIRO Australian National Fish Collection. They studied 230 samples from fishes (consisting of >160 fish species). An optimized formalin-fixed, paraffin-embedded DNA extraction method resulted in usable DNA from degraded tissues. Four mini barcoding assays of the mitochondrial DNA (mtDNA) were characterized with Sanger and Illumina amplicon sequencing. In the good quality DNA (without exposure to formalin), up to 88% of the specimens were correctly matched at the species level using the cytochrome oxidase subunit 1 (COI) mini barcodes, whereas up to 58% of the specimens exposed to formalin for less than 8 weeks were correctly identified to species. In contrast, 16S primers provided higher amplification success with formalin-exposed tissues, although the COI gene was more successful for identification. Importantly, the authors found that DNA of a certain size and quality can be amplified and sequenced despite exposure to formalin, and Illumina sequencing provided them with greater power of resolution for taxa identification even when there was little DNA present. Overall, within parameter constraints, this study highlights the possibilities of recovering DNA barcodes for identification from formalin-fixed fish specimens, and the authors provide guidelines for when successful identification could be expected.

Response to Zamani et al. (2020): The omission of critical data in the pursuit of "revolutionary" methods to accelerate the description of species

Here we respond to the criticisms leveled against a proposal that suggested an efficient solution to the taxonomic impediment. We clarify some of our objectives and demonstrate that many of the criticisms apply more to traditional approaches to taxonomy rather than to our minimalist approach.

An Integrated Molecular Approach to Untangling Host-Vector-Pathogen Interactions in Mosquitoes (Diptera: Culicidae) From Sylvan Communities in Mexico

There are ~240 species of Culicidae in Mexico, of which some are vectors of arthropod-borne viruses such as Zika virus, dengue virus, chikungunya virus, and West Nile virus. Thus, the identification of mosquito feeding preferences is paramount to understanding of vector–host–pathogen interactions that, in turn, can aid the control of disease outbreaks. Typically, DNA and RNA are extracted separately for animal (insects and blood meal hosts) and viral identification, but this study demonstrates that multiple organisms can be analyzed from a single RNA extract. For the first time, residual DNA present in standard RNA extracts was analyzed by DNA barcoding in concert with Sanger and next-generation sequencing (NGS) to identify both the mosquito species and the source of their meals in blood-fed females caught in seven sylvan communities in Chiapas State, Mexico. While mosquito molecular identification involved standard barcoding methods, the sensitivity of blood meal identification was maximized by employing short primers with NGS. In total, we collected 1,634 specimens belonging to 14 genera, 25 subgenera, and 61 morphospecies of mosquitoes. Of these, four species were new records for Mexico (Aedes guatemala, Ae. insolitus, Limatus asulleptus, Trichoprosopon pallidiventer), and nine were new records for Chiapas State. DNA barcode sequences for >300 bp of the COI gene were obtained from 291 specimens, whereas 130 bp sequences were recovered from another 179 specimens. High intraspecific divergence values (>2%) suggesting cryptic species complexes were observed in nine taxa: Anopheles eiseni (5.39%), An. pseudopunctipennis (2.79%), Ae. podographicus (4.05%), Culex eastor (4.88%), Cx. erraticus (2.28%), Toxorhynchites haemorrhoidalis (4.30%), Tr. pallidiventer (4.95%), Wyeomyia adelpha/Wy. guatemala (7.30%), and Wy. pseudopecten (4.04%). The study increased the number of mosquito species known from 128 species to 138 species for Chiapas State, and 239 for Mexico as a whole. Blood meal analysis showed that Aedes angustivittatus fed on ducks and chicken, whereas Psorophora albipes fed on humans. Culex quinquefasciatus fed on diverse hosts including chicken, human, turkey, and Mexican grackle. No arbovirus RNA was detected by reverse transcriptase–polymerase chain reaction in the surveyed specimens. This study demonstrated, for the first time, that residual DNA present in RNA blood meal extracts can be used to identify host vectors, highlighting the important role of molecular approaches in both vector identification and revealing host–vector–pathogen interactions.

From e-voucher to genomic data: Preserving archive specimens as demonstrated with medically important mosquitoes (Diptera: Culicidae) and kissing bugs (Hemiptera: Reduviidae)

Scientific collections such as the U.S. National Museum (USNM) are critical to filling knowledge gaps in molecular systematics studies. The global taxonomic impediment has resulted in a reduction of expert taxonomists generating new collections of rare or understudied taxa and these large historic collections may be the only reliable source of material for some taxa. Integrated systematics studies using both morphological examinations and DNA sequencing are often required for resolving many taxonomic issues but as DNA methods often require partial or complete destruction of a sample, there are many factors to consider before implementing destructive sampling of specimens within scientific collections. We present a methodology for the use of archive specimens that includes two crucial phases: 1) thoroughly documenting specimens destined for destructive sampling—a process called electronic vouchering, and 2) the pipeline used for whole genome sequencing of archived specimens, from extraction of genomic DNA to assembly of putative genomes with basic annotation. The process is presented for eleven specimens from two different insect subfamilies of medical importance to humans: Anophelinae (Diptera: Culicidae)—mosquitoes and Triatominae (Hemiptera: Reduviidae)—kissing bugs. Assembly of whole mitochondrial genome sequences of all 11 specimens along with the results of an ortholog search and BLAST against the NCBI nucleotide database are also presented.

Evaluating DNA Barcoding for Species Identification and Discovery in European Gracillariid Moths

Gracillariidae is the most species-rich leaf-mining moth family with over 2,000 described species worldwide. In Europe, there are 263 valid named species recognized, many of which are difficult to identify using morphology only. Here we explore the use of DNA barcodes as a tool for identification and species discovery in European gracillariids. We present a barcode library including 6,791 COI sequences representing 242 of the 263 (92%) resident species. Our results indicate high congruence between morphology and barcodes with 91.3% (221/242) of European species forming monophyletic clades that can be identified accurately using barcodes alone. The remaining 8.7% represent cases of non-monophyly making their identification uncertain using barcodes. Species discrimination based on the Barcode Index Number system (BIN) was successful for 93% of species with 7% of species sharing BINs. We discovered as many as 21 undescribed candidate species, of which six were confirmed from an integrative approach; the other 15 require additional material and study to confirm preliminary evidence. Most of these new candidate species are found in mountainous regions of Mediterranean countries, the South-Eastern Alps and the Balkans, with nine candidate species found only on islands. In addition, 13 species were classified as deep conspecific lineages, comprising a total of 27 BINs with no intraspecific morphological differences found, and no known ecological differentiation. Double-digest restriction-site associated DNA sequencing (ddRAD) analysis showed strong mitonuclear discrepancy in four out of five species studied. This discordance is not explained by Wolbachia-mediated genetic sweeps. Finally, 26 species were classified as “unassessed species splits” containing 71 BINs and some involving geographical isolation or ecological specialization that will require further study to test whether they represent new cryptic species.

A SMRT approach for targeted amplicon sequencing of museum specimens (Lepidoptera)-patterns of nucleotide misincorporation

Natural history collections are a valuable resource for molecular taxonomic studies and for examining patterns of evolutionary diversification, particularly in the case of rare or extinct species. However, the recovery of sequence information is often complicated by DNA degradation. This article describes use of the Sequel platform (Pacific Biosciences) to recover the 658 bp barcode region of the mitochondrial cytochrome c oxidase I (COI) gene from 380 butterflies with an average age of 50 years. Nested multiplex PCR was employed for library preparation to facilitate sequence recovery from extracts with low concentrations of highly degraded DNA. By employing circular consensus sequencing (CCS) of short amplicons (circa 150 bp), full-length barcodes could be assembled without a reference sequence, an important advance from earlier protocols which required reference sequences to guide contig assembly. The Sequel protocol recovered COI sequences (499 bp on average) from 318 of 380 specimens (84%), much higher than for Sanger sequencing (26%). Because each read derives from a single molecule, it was also possible to quantify the incidence of substitutions arising from DNA damage. In agreement with past work on sequence changes induced by DNA degradation, the transition C/G → T/A was the most prevalent category of change, but its rate of occurrence (4.58E−4) was so low that it did not impede the recovery of reliable sequences. Because the current protocol recovers COI sequence from most museum specimens, and because sequence fidelity is unaffected by nucleotide misincorporations, large-scale sequence characterization of museum specimens is feasible.

A taxonomic revision of the Archipini of the Caribbean (Lepidoptera, Tortricidae, Tortricinae)

The Archipini fauna of the Caribbean is revised to include 33 species. Most previously described species occurring in the region are redescribed and figured, with 13 new species: Argyrotaeniabrownisp. nov., A.crypticasp. nov. (including A.c.crypticassp. nov. and A.c.praeteritanassp. nov.), A.paradiseisp. nov., A.razowskianasp. nov., Claduncariarawlinsanasp. nov., Cla.praedictanasp. nov., Cla.tainosp. nov., Clepsisdavisisp. nov., Cle.deronisp. nov., Cle.jamesstewartisp. nov., Cle.peroniaesp. nov., Mictocommosislesleyaesp. nov., and Mictopsichianyhllindasp. nov. Three new combinations are proposed: Claduncariamesosignaria (Razowski, 1999), comb. nov. (including Argyrotaeniathamaluncus Razowski, 1999, syn. nov.), Claduncariaminisignaria (Razowski, 1999), comb. nov., and Claduncariachalarostium (Razowski & Becker, 2000b), comb. nov., stat. nov.Argyrotaeniagranpiedrae Razowski & Becker, 2010 is reduced to subspecies rank under Argyrotaeniaceramica Razowski, 1999, resulting in Argyrotaeniaceramicagranpiedrae Razowski & Becker, 2010, stat. nov. Four new synonymies are proposed: Clepsislabisclera Razowski & Becker, 2010, syn. nov. as junior synonym of Claduncariamaestrana Razowski & Becker, 2010; Clepsispinaria Razowski & Becker, 2010, syn. nov. as junior synonym of Clepsisperitana (Clemens, 1860); and Argyrotaenianeibana Razowski, 1999, syn. nov. and A.ochrochroa Razowski, 1999 syn. nov. as junior synonyms of Argyrotaeniaamatana (Dyar, 1901). Males of Argyrotaeniafelisana Razowski, 1999, A.nuezana Razowski, 1999, and Claduncariaminisignaria (Razowski, 1999), comb. nov. are described for the first time; females of Argyrotaeniajamaicana (Razowski & Becker, 2000a) and Claduncariaochrochlaena (Razowski, 1999) are described for the first time. The concept of Claduncaria is expanded and its diagnosis is modified to more clearly define its generic boundaries. A unique external sexual coupling mechanism in Claduncaria is discussed. Keys to the genera and species of Caribbean Archipini, distribution maps, a regional checklist, and Neighbor-joining and Maximum Likelihood trees based on COI barcode data are provided. Phylogenetic relationships among Caribbean Archipini are briefly discussed.

The Origins of Coca: Museum Genomics Reveals Multiple Independent Domestications from Progenitor Erythroxylum gracilipes

Coca is the natural source of cocaine as well as a sacred and medicinal plant farmed by South American Amerindians and mestizos. The coca crop comprises four closely related varieties classified into two species (Amazonian and Huánuco varieties within Erythroxylum coca Lam., and Colombian and Trujillo varieties within Erythroxylum novogranatense (D. Morris) Hieron.) but our understanding of the domestication and evolutionary history of these taxa is nominal. In this study, we use genomic data from natural history collections to estimate the geographic origins and genetic diversity of this economically and culturally important crop in the context of its wild relatives. Our phylogeographic analyses clearly demonstrate the four varieties of coca comprise two or three exclusive groups nested within the diverse lineages of the widespread, wild species Erythroxylum gracilipes; establishing a new and robust hypothesis of domestication wherein coca originated two or three times from this wild progenitor. The Colombian and Trujillo coca varieties are descended from a single, ancient domestication event in northwestern South America. Huánuco coca was domesticated more recently, possibly in southeastern Peru. Amazonian coca either shares a common domesticated ancestor with Huánuco coca, or it was the product of a third and most recent independent domestication event in the western Amazon basin. This chronology of coca domestication reveals different Holocene peoples in South America were able to independently transform the same natural resource to serve their needs; in this case, a workaday stimulant. [Erythroxylum; Erythroxylaceae; Holocene; Museomics; Neotropics; phylogeography; plant domestication; target-sequence capture.]

Megacraspedus cottiensis sp. nov. (Lepidoptera, Gelechiidae) from northern Italy – a case of taxonomic confusion

Megacraspeduscottiensissp. nov. is described from the western Alps (prov. Torino, Italy). The dorsal habitus and genitalia for both the male and brachypterous female are provided. The new species belongs to the M.faunierensis species group based on genitalia morphology and DNA barcodes, and was hitherto confused with M.neli Huemer & Karsholt, 2018 from the southwestern Alps. However, it clearly differs in morphology and DNA barcode sequences from that species and from M.faunierensis Huemer & Karsholt, 2018. The new species is suspected of being a regional endemic of the Cottian Alps.

Next generation sequencing-aided comprehensive geographic coverage sheds light on the status of rare and extinct populations of Aporia butterflies (Lepidoptera: Pieridae)

The Black-veined White Aporia crataegi (Linnaeus, 1758), a common and widespread butterfly ranging from northwestern Africa to Europe and Asia, has been extinct in Britain since the 1920s and is on a steady decline in several other parts of its range. In order to investigate genetic diversity within A. crataegi and its correspondence with current subspecies-level taxonomy, we barcoded 173 specimens from across its range including, for the first time, extinct populations from Britain and Korea. Using next generation sequencing we also obtained a sequence for Aporia joubini, a peculiar taxon from China known only by its type specimen collected in the early twentieth century. Our phylogenetic analysis placed A. joubini sister to A. oberthuri, although further taxon sampling may reveal a different scheme. Within A. crataegi, we observed a shallow and weak mitogenomic structure with only a few distinct lineages in North Africa, Sicily, Iran, and Japan. Eurasian populations, including those extinct in Britain and Korea, clustered into a large set of closely allied lineages, consistent with a recent expansion during the Late Pleistocene glacial period. This study highlights the importance of museum collections and the unique opportunities they provide in documenting species diversity and helping conservation efforts.

Advantages of an easy-to-use DNA extraction method for minimal-destructive analysis of collection specimens

Here we present and justify an approach for minimal-destructive DNA extraction from historic insect specimens for next generation sequencing applications. An increasing number of studies use insects from museum collections for biodiversity research. However, the availability of specimens for molecular analyses has been limited by the degraded nature of the DNA gained from century-old museum material and the consumptive nature of most DNA extraction procedures. The method described in this manuscript enabled us to successfully extract DNA from specimens as old as 241 years using a minimal-destructive approach. The direct comparison of the DNeasy extraction Kit and the Monarch® PCR & DNA Clean-up Kit showed a significant increase of 17.3-fold higher DNA yield extracted with the Monarch Oligo protocol on average. By using an extraction protocol originally designed for oligonucleotide clean-up, we were able to combine overcoming the restrictions by target fragment size and strand state, with minimising time consumption and labour-intensity. The type specimens used for the minimal-destructive DNA extraction exhibited no significant external change or post-extraction damage, while sufficient DNA was retrieved for analyses.

Phylogenetic reassignment of basal cyclostome braconid parasitoid wasps (Hymenoptera) with description of a new, enigmatic Afrotropical tribe with a highly anomalous 28S D2 secondary structure

A new tribe of braconid wasps provisionally included in the Rhyssalinae, Laibaleini trib. nov., type genus Laibalea gen. nov. (type species Laibalea enigmatica sp. nov.), from Kenya and the Central African Republic, is described. A molecular dataset, with emphasis on basally derived taxa based on four gene fragments (28S D2–D3 expansion region, COI barcode, elongation factor 1-alpha and 16S ribosomal DNA), was analysed both alone and in combination with a morphological dataset. Molecular phylogenetic placement of the new species into an existing subfamily is complicated by the extreme sequence divergence of the three sequences obtained for Laibalea. In both the combined sequence analysis and the combined DNA plus morphological tree, Laibalea is recovered as a sister group to the Rhyssalinae plus all non-cyclostome lineage braconids excluding Mesostoinae, Maxfischeriinae and Aphidiinae. A consensus of morphological characters and molecular analyses suggests inclusion of Laibalea either in the otherwise principally Holarctic subfamily Rhyssalinae or perhap more basally, in the principally Gondwanan Mesostoinae s.l., although we cannot exclude the possibility that it might represent a separate basal lineage. We place Laibalea in its own tribe, provisionally included in Rhyssalinae. The DNA sequence data are presented for several genera for the first time. Avga, the type genus of Avgini, is shown not to belong to Mesostoinae s.l. or Hormiinae, but its exact relationships remain uncertain. The generic compositions of Rhyssalinae and Mesostoinae s.l. are revised. Anachyra, Apoavga, Neptihormius, Neoavga and Opiopterus are shown to belong to Mesostoinae s.s. A key to the tribes of Rhyssalinae is provided.

Genomes reveal drastic and recurrent phenotypic divergence in firetip skipper butterflies (Hesperiidae: Pyrrhopyginae)

Biologists marvel at the powers of adaptive convergence, when distantly related animals look alike. While mimetic wing patterns of butterflies have fooled predators for millennia, entomologists inferred that mimics were distant relatives despite similar appearance. However, the obverse question has not been frequently asked. Who are the close relatives of mimetic butterflies and what are their features? As opposed to close convergence, divergence from a non-mimetic relative would also be extreme. When closely related animals look unalike, it is challenging to pair them. Genomic analysis promises to elucidate evolutionary relationships and shed light on molecular mechanisms of divergence. We chose the firetip skipper butterfly as a model due to its phenotypic diversity and abundance of mimicry. We sequenced and analysed whole genomes of nearly 120 representative species. Genomes partitioned this subfamily Pyrrhopyginae into five tribes (1 new), 23 genera and, additionally, 22 subgenera (10 new). The largest tribe Pyrrhopygini is divided into four subtribes (three new). Surprisingly, we found five cases where a uniquely patterned butterfly was formerly placed in a genus of its own and separately from its close relatives. In several cases, extreme and rapid phenotypic divergence involved not only wing patterns but also the structure of the male genitalia. The visually striking wing pattern difference between close relatives frequently involves disappearance or suffusion of spots and colour exchange between orange and blue. These differences (in particular, a transition between unspotted black and striped wings) happen recurrently on a short evolutionary time scale, and are therefore probably achieved by a small number of mutations.

A method to generate multilocus barcodes of pinned insect specimens using MiSeq

For molecular insect identification, amplicon sequencing methods are recommended because they offer a cost-effective approach for targeting small sets of informative genes from multiple samples. In this context, high-throughput multilocus amplicon sequencing has been achieved using the MiSeq Illumina sequencing platform. However, this approach generates short gene fragments of <500 bp, which then have to be overlapped using bioinformatics to achieve longer sequence lengths. This increases the risk of generating chimeric sequences or leads to the formation of incomplete loci. Here, we propose a modified nested amplicon sequencing method for targeting multiple loci from pinned insect specimens using the MiSeq Illumina platform. The modification exists in using a three-step nested PCR approach targeting near full-length loci in the initial PCR and subsequently amplifying short fragments of between 300 and 350 bp for high-throughput sequencing using Illumina chemistry. Using this method, we generated 407 sequences of three loci from 86% of all the specimens sequenced. Out of 103 pinned bee specimens of replicated species, 71% passed the 95% sequence similarity threshold between species replicates. This method worked best for pinned specimens aged between 0 and 5 years, with a limit of 10 years for pinned and 14 years for ethanol-preserved specimens. Hence, our method overcomes some of the challenges of amplicon sequencing using short read next generation sequencing and improves the possibility of creating high-quality multilocus barcodes from insect collections.

Evaluation of DNA degradation and establishment of a degradation analysis model for Lepidoptera specimens

Millions of museum specimens are integral to biodiversity studies; however, DNA degradation may limit the ability to obtain DNA sequences. In this study, a degradation analysis model for Lepidoptera specimens was established. Based on this model, we revealed the characteristics of DNA fragment distribution caused by external DNA damage factors during specimen preservation. We found that the degree of DNA degradation increased over time; DNA degradation of spread and dried adult specimens was significantly higher than that in the folded and formalin-fixed larval specimens. However, the effects of folding wings on DNA degradation and the effects of the preservation method/stage (formalin-fixed larval vs air-dried adult specimens) were different for different species.

Twenty-six new species of Hoploscopa (Lepidoptera, Crambidae) from South-East Asia revealed by morphology and DNA barcoding

Hoploscopa Meyrick (Lepidoptera: Crambidae) is a fern-feeding genus found in montane areas of South-East Asia and Melanesia, eastwards up to the Samoan Islands. It includes sixteen described species, with at least 70 further undescribed species known from scientific collections. An iterative approach including morphological and molecular characters was used in order to explore the diversity of Hoploscopa. The hitherto described species are revised, and descriptions authored by T. Léger and M. Nuss are provided for an additional 26 new species: H.agtuuganonensissp. nov., H.albipunctasp. nov., H.albomaculatasp. nov., H.anacanthasp. nov., H.boletasp. nov., H.cynodontasp. nov., H.danaoensissp. nov., H.gombongisp. nov., H.gracilissp. nov., H.ignitamaculaesp. nov., H.isarogensissp. nov., H.jubatasp. nov., H.kelamasp. nov., H.kinabaluensissp. nov., H.mallyisp. nov., H.marijoweissaesp. nov., H.matheaesp. nov., H.niveofasciasp. nov., H.pangrangoensissp. nov., H.parvimaculasp. nov., H.pseudometacrossasp. nov., H.sepanggisp. nov., H.sumatrensissp. nov., H.titikasp. nov., H.tonsepisp. nov., H.ypsilonsp. nov. Using a protocol specific for the amplification of DNA from old museum specimens, we recovered 101 COI barcodes for all but one of the newly described species, with 76 being barcode compliant (>487 bp). Species delimitation analyses suggest cryptic diversity, with six cases reflecting allopatric divergence, and two further cases found in sympatry.

A reference library for Canadian invertebrates with 1.5 million barcodes, voucher specimens, and DNA samples

The reliable taxonomic identification of organisms through DNA sequence data requires a well parameterized library of curated reference sequences. However, it is estimated that just 15% of described animal species are represented in public sequence repositories. To begin to address this deficiency, we provide DNA barcodes for 1,500,003 animal specimens collected from 23 terrestrial and aquatic ecozones at sites across Canada, a nation that comprises 7% of the planet's land surface. In total, 14 phyla, 43 classes, 163 orders, 1123 families, 6186 genera, and 64,264 Barcode Index Numbers (BINs; a proxy for species) are represented. Species-level taxonomy was available for 38% of the specimens, but higher proportions were assigned to a genus (69.5%) and a family (99.9%). Voucher specimens and DNA extracts are archived at the Centre for Biodiversity Genomics where they are available for further research. The corresponding sequence and taxonomic data can be accessed through the Barcode of Life Data System, GenBank, the Global Biodiversity Information Facility, and the Global Genome Biodiversity Network Data Portal.

Phylogenetic position of the 'extinct' Fijian coconut moth, Levuana iridescens (Lepidoptera: Zygaenidae)

Levuana iridescens Bethune-Baker, 1906, a day-flying moth purported to be endemic to the Fijian Island of Viti Levu and a former pest of its coconut palm trees, was last observed in 1956 and has been officially declared extinct by IUCN since 1996. The controversial classical biological control method that resulted in the (presumed) demise of this moth has given this species an iconic status in biological control studies. We investigated the sister-group relationships and phylogenetic placement of this moth using NGS-obtained ancient DNA sequences from museum specimens of L. iridescens collected in the 1920s, combined with 31 morphological characters used in earlier studies and 2 new characters. Our findings show that Levuana is most closely related to the Australian genus Myrtartona. The significance of these findings is discussed.

Validation of COI metabarcoding primers for terrestrial arthropods

Metabarcoding can rapidly determine the species composition of bulk samples and thus aids biodiversity and ecosystem assessment. However, it is essential to use primer sets that minimize amplification bias among taxa to maximize species recovery. Despite this fact, the performance of primer sets employed for metabarcoding terrestrial arthropods has not been sufficiently evaluated. This study tests the performance of 36 primer sets on a mock community containing 374 insect species. Amplification success was assessed with gradient PCRs and the 21 most promising primer sets selected for metabarcoding. These 21 primer sets were also tested by metabarcoding a Malaise trap sample. We identified eight primer sets, mainly those including inosine and/or high degeneracy, that recovered more than 95% of the species in the mock community. Results from the Malaise trap sample were congruent with the mock community, but primer sets generating short amplicons produced potential false positives. Taxon recovery from both mock community and Malaise trap sample metabarcoding were used to select four primer sets for additional evaluation at different annealing temperatures (40-60 °C) using the mock community. The effect of temperature varied by primer pair but overall it only had a minor effect on taxon recovery. This study reveals the weak performance of some primer sets employed in past studies. It also demonstrates that certain primer sets can recover most taxa in a diverse species assemblage. Thus, based our experimental set up, there is no need to employ several primer sets targeting the same gene region. We identify several suitable primer sets for arthropod metabarcoding, and specifically recommend BF3 + BR2, as it is not affected by primer slippage and provides maximal taxonomic resolution. The fwhF2 + fwhR2n primer set amplifies a shorter fragment and is therefore ideal when targeting degraded DNA (e.g., from gut contents).

DNA barcode reference libraries for the monitoring of aquatic biota in Europe: Gap-analysis and recommendations for future work

Effective identification of species using short DNA fragments (DNA barcoding and DNA metabarcoding) requires reliable sequence reference libraries of known taxa. Both taxonomically comprehensive coverage and content quality are important for sufficient accuracy. For aquatic ecosystems in Europe, reliable barcode reference libraries are particularly important if molecular identification tools are to be implemented in biomonitoring and reports in the context of the EU Water Framework Directive (WFD) and the Marine Strategy Framework Directive (MSFD). We analysed gaps in the two most important reference databases, Barcode of Life Data Systems (BOLD) and NCBI GenBank, with a focus on the taxa most frequently used in WFD and MSFD. Our analyses show that coverage varies strongly among taxonomic groups, and among geographic regions. In general, groups that were actively targeted in barcode projects (e.g. fish, true bugs, caddisflies and vascular plants) are well represented in the barcode libraries, while others have fewer records (e.g. marine molluscs, ascidians, and freshwater diatoms). We also found that species monitored in several countries often are represented by barcodes in reference libraries, while species monitored in a single country frequently lack sequence records. A large proportion of species (up to 50%) in several taxonomic groups are only represented by private data in BOLD. Our results have implications for the future strategy to fill existing gaps in barcode libraries, especially if DNA metabarcoding is to be used in the monitoring of European aquatic biota under the WFD and MSFD. For example, missing species relevant to monitoring in multiple countries should be prioritized for future collaborative programs. We also discuss why a strategy for quality control and quality assurance of barcode reference libraries is needed and recommend future steps to ensure full utilisation of metabarcoding in aquatic biomonitoring.

Metabarcoding a diverse arthropod mock community

Although DNA metabarcoding is an attractive approach for monitoring biodiversity, it is often difficult to detect all the species present in a bulk sample. In particular, sequence recovery for a given species depends on its biomass and mitome copy number as well as the primer set employed for PCR. To examine these variables, we constructed a mock community of terrestrial arthropods comprised of 374 species. We used this community to examine how species recovery was impacted when amplicon pools were constructed in four ways. The first two protocols involved the construction of bulk DNA extracts from different body segments (Bulk Abdomen, Bulk Leg). The other protocols involved the production of DNA extracts from single legs which were then merged prior to PCR (Composite Leg) or PCR‐amplified separately (Single Leg) and then pooled. The amplicons generated by these four treatments were then sequenced on three platforms (Illumina MiSeq, Ion Torrent PGM and Ion Torrent S5). The choice of sequencing platform did not substantially influence species recovery, although the Miseq delivered the highest sequence quality. As expected, species recovery was most efficient from the Single Leg treatment because amplicon abundance varied little among taxa. Among the three treatments where PCR occurred after pooling, the Bulk Abdomen treatment produced a more uniform read abundance than the Bulk Leg or Composite Leg treatment. Primer choice also influenced species recovery and evenness. Our results reveal how variation in protocols can have substantial impacts on perceived diversity unless sequencing coverage is sufficient to reach an asymptote.

Saving DNA from museum specimens: The success of DNA mini-barcodes in haplotype reconstruction in the genus Anastrepha (Diptera: Tephritidae)

The fragmentation of DNA in historical specimens is very common, so obtaining sequences that allow molecular identification and the study of diversity is quite challenging. In this study, we used preserved and fresh specimens of the fruit fly genus Anastrepha, a genus of economic impact of fruit crops of the Neotropic. From these specimens, we evaluated: (1) the success PCR amplification rates of mini-barcodes fragments of the cytochrome c oxidase subunit I (COI) gene, and (2) the usefulness of mini-barcodes in the reconstruction of haplotypes for the identification of species and the diversity analysis. We used 93 specimens from 12 species, which had been preserved in 70% ethanol for more than 20 years. Internal primers were designed in the COI region and primers available in the literature were also evaluated. We obtained amplifications for 62.36% of the samples processed, and reconstructed haplotypes between 171 bp and 632 bp. Variable amplification rates between combinations of primers and between species were obtained, and molecular identification of some museum specimens was achieved. It was also possible to compare the haplotypes obtained in four species from which both fresh and museum samples were available. Our results also show the importance of the adjustment of the primers for the amplification, allowing to amplify fragments of up to 400 bp. The use available resources in biological collections is key to increasing knowledge of species of interest, and by means of the amplification of mini-barcodes, short sequences can be obtained that allow the molecular identification of specimens and the reconstruction of haplotypes with multiple purposes.

Expedited assessment of terrestrial arthropod diversity by coupling Malaise traps with DNA barcoding 1

Monitoring changes in terrestrial arthropod communities over space and time requires a dramatic increase in the speed and accuracy of processing samples that cannot be achieved with morphological approaches. The combination of DNA barcoding and Malaise traps allows expedited, comprehensive inventories of species abundance whose cost will rapidly decline as high-throughput sequencing technologies advance. Aside from detailing protocols from specimen sorting to data release, this paper describes their use in a survey of arthropod diversity in a national park that examined 21 194 specimens representing 2255 species. These protocols can support arthropod monitoring programs at regional, national, and continental scales.

Use of genetic, climatic, and microbiological data to inform reintroduction of a regionally extinct butterfly

Species reintroductions are increasingly used as means of mitigating biodiversity loss. Besides habitat quality at the site targeted for reintroduction, the choice of source population can be critical for success. The butterfly Melanargia russiae (Esper´s marbled white) was extirpated from Hungary over 100 years ago, and a reintroduction program has recently been approved. We used museum specimens of this butterfly, mitochondrial DNA data (mtDNA), endosymbiont screening, and climatic-similarity analyses to determine which extant populations should be used for its reintroduction. The species displayed 2 main mtDNA lineages across its range: 1 restricted to Iberia and southern France (Iberian lineage) and another found throughout the rest of its range (Eurasian lineage). These 2 lineages possessed highly divergent wsp alleles of the bacterial endosymbiont Wolbachia. The century-old Hungarian specimens represented an endemic haplotype belonging to the Eurasian lineage, differing by one mutation from the Balkan and eastern European populations. The Hungarian populations of M. russiae occurred in areas with a colder and drier climate relative to most sites with extant known populations. Our results suggest the populations used for reintroduction to Hungary should belong to the Eurasian lineage, preferably from eastern Ukraine (genetically close and living in areas with the highest climatic similarity). Materials stored in museum collections can provide unique opportunities to document historical genetic diversity and help direct conservation.

Advancing taxonomy and bioinventories with DNA barcodes

We use three examples—field and ecology-based inventories in Costa Rica and Papua New Guinea and a museum and taxonomic-based inventory of the moth family Geometridae—to demonstrate the use of DNA barcoding (a short sequence of the mitochondrial COI gene) in biodiversity inventories, from facilitating workflows of identification of freshly collected specimens from the field, to describing the overall diversity of megadiverse taxa from museum collections, and most importantly linking the fresh specimens, the general museum collections and historic type specimens. The process also flushes out unexpected sibling species hiding under long-applied scientific names, thereby clarifying and parsing previously mixed collateral data. The Barcode of Life Database has matured to an essential interactive platform for the multi-authored and multi-process collaboration. The BIN system of creating and tracking DNA sequence-based clusters as proxies for species has become a powerful way around some parts of the ‘taxonomic impediment’, especially in entomology, by providing fast but testable and tractable species hypotheses, tools for visualizing the distribution of those in time and space and an interim naming system for communication.

This article is part of the themed issue ‘From DNA barcodes to biomes’.