The efficacy of DNA barcoding in the classification, genetic differentiation, and biodiversity assessment of benthic macroinvertebrates

Delimiting species, revealing cryptic diversity in Molytinae (Coleoptera: Curculionidae) weevil through DNA barcoding

The subfamily Molytinae (Coleoptera: Curculionidae), being the second largest group within the family Curculionidae, exhibits a diverse range of hosts and poses a serious threat to agricultural and forestry industries. We used 1,290 cytochrome c oxidase subunit I (COI) barcodes to assess the efficiency of COI barcodes in species differentiation and uncover cryptic species diversity within weevils of Molytinae. The average Kimura 2-parameter distances within species, genus, and subfamily were 2.90%, 11.0%, and 22.26%, respectively, indicating significant genetic differentiation at both levels. Moreover, there exists a considerable degree of overlap between intraspecific (0%-27.50%) and interspecific genetic distances (GDs; 0%-39.30%). The application of Automatic barcode gap discovery, Assemble Species by Automatic Partitioning, Barcode Index Number, Poisson Tree Processes (PTP), Bayesian Poisson Tree Processes (bPTP), and jMOTU resulted in the identification of 279, 275, 494, 322, 320, and 279 molecular operational taxonomic units, respectively. The integration of 6 methods successfully delimited species of Molytinae in 86.6% of all examined morphospecies, surpassing a threshold value of 3% GD (73.0%). A total of 28 morphospecies exhibiting significant intraspecific divergences were assigned to multiple MOTUs, respectively, suggesting the presence of cryptic diversity or population divergence. The identification of cryptic species within certain morphological species in this study necessitates further investigation through comprehensive taxonomic practices in the future.

Delimiting species, revealing cryptic diversity, and population divergence in Qinghai-Tibet Plateau weevils through DNA barcoding

The Leptomias group represents one of the most diverse taxonomic group of weevils in the Qinghai-Tibet Plateau and its adjacent areas. Despite the potential of hidden diversity, relatively few comprehensive studies have been conducted on species diversity in this taxonomic group. In this study, we performed DNA barcoding analysis for species of the Leptomias group using a comprehensive DNA barcode dataset that included 476 sequences representing 54 morphospecies. Within the dataset, our laboratory contributed 474 sequences, and 390 sequences were newly generated for this study. The average Kimura 2-parameter distances among morphospecies and genera were 0.76% and 19.15%, respectively. In 94.4% of the species, the minimum interspecific distances exceeded the maximum intraspecific distances, indicating the presence of barcode gaps in most species of Leptomias group. The application of Automatic Barcode Gap Discovery, Assemble Species by Automatic Partitioning, Barcode Index Number, Bayesian Poisson tree processes, jMOTU, and Neighbor-joining tree methods revealed 45, 45, 63, 54, and 55 distinct clusters representing single species, respectively. Additionally, a total of four morphospecies, Leptomias kangmarensis, L. midlineatus, L. siahus, and L. sp.9RL, were found to be assigned to multiple subclade each, indicating the geographical divergences and the presence of cryptic diversity. Our findings of this study demonstrate that Qinghai-Tibet Plateau exhibits a higher species diversity of the Leptomias group, and it is imperative to investigate cryptic species within certain morphospecies using integrative taxonomic approaches in future studies. Moreover, the construction of a DNA barcode reference library presented herein establishes a robust foundational dataset to support forthcoming research on weevil taxonomy, phylogenetics, ecology, and evolution.

Three steps towards comparability and standardization among molecular methods for characterizing insect communities

Molecular methods are currently some of the best-suited technologies for implementation in insect monitoring. However, the field is developing rapidly and lacks agreement on methodology or community standards. To apply DNA-based methods in large-scale monitoring, and to gain insight across commensurate data, we need easy-to-implement standards that improve data comparability. Here, we provide three recommendations for how to improve and harmonize efforts in biodiversity assessment and monitoring via metabarcoding: (i) we should adopt the use of synthetic spike-ins, which will act as positive controls and internal standards; (ii) we should consider using several markers through a multiplex polymerase chain reaction (PCR) approach; and (iii) we should commit to the publication and transparency of all protocol-associated metadata in a standardized fashion. For (i), we provide a ready-to-use recipe for synthetic cytochrome c oxidase spike-ins, which enable between-sample comparisons. For (ii), we propose two gene regions for the implementation of multiplex PCR approaches, thereby achieving a more comprehensive community description. For (iii), we offer guidelines for transparent and unified reporting of field, wet-laboratory and dry-laboratory procedures, as a key to making comparisons between studies. Together, we feel that these three advances will result in joint quality and calibration standards rather than the current laboratory-specific proof of concepts. This article is part of the theme issue 'Towards a toolkit for global insect biodiversity monitoring'.

Integrative species delimitation and five new species of lynx spiders (Araneae, Oxyopidae) in Taiwan

An accurate assessment of species diversity is a cornerstone of biology and conservation. The lynx spiders (Araneae: Oxyopidae) represent one of the most diverse and widespread cursorial spider groups, however their species richness in Asia is highly underestimated. In this study, we revised species diversity with extensive taxon sampling in Taiwan and explored species boundaries based on morphological traits and genetic data using a two-step approach of molecular species delimitation. Firstly, we employed a single COI dataset and applied two genetic distance-based methods: ABGD and ASAP, and two topology-based methods: GMYC and bPTP. Secondly, we further analyzed the lineages that were not consistently delimited, and incorporated H3 to the dataset for a coalescent-based analysis using BPP. A total of eight morphological species were recognized, including five new species, Hamataliwa cordivulva sp. nov., Hamat. leporauris sp. nov., Tapponia auriola sp. nov., T. parva sp. nov. and T. rarobulbus sp. nov., and three newly recorded species, Hamadruas hieroglyphica (Thorell, 1887), Hamat. foveata Tang & Li, 2012 and Peucetia latikae Tikader, 1970. All eight morphological species exhibited reciprocally monophyletic lineages. The results of molecular-based delimitation analyses suggested a variety of species hypotheses that did not fully correspond to the eight morphological species. We found that Hamat. cordivulva sp. nov. and Hamat. foveata showed shallow genetic differentiation in the COI, but they were unequivocally distinguishable according to their genitalia. In contrast, T. parva sp. nov. represented a deep divergent lineage, while differences of genitalia were not detected. This study highlights the need to comprehensively employ multiple evidence and methods to delineate species boundaries and the values of diagnostic morphological characters for taxonomic studies in lynx spiders.

Current Status of Omics in Biological Quality Elements for Freshwater Biomonitoring

Freshwater ecosystems have been experiencing various forms of threats, mainly since the last century. The severity of this adverse scenario presents unprecedented challenges to human health, water supply, agriculture, forestry, ecological systems, and biodiversity, among other areas. Despite the progress made in various biomonitoring techniques tailored to specific countries and biotic communities, significant constraints exist, particularly in assessing and quantifying biodiversity and its interplay with detrimental factors. Incorporating modern techniques into biomonitoring methodologies presents a challenging topic with multiple perspectives and assertions. This review aims to present a comprehensive overview of the contemporary advancements in freshwater biomonitoring, specifically by utilizing omics methodologies such as genomics, metagenomics, transcriptomics, proteomics, metabolomics, and multi-omics. The present study aims to elucidate the rationale behind the imperative need for modernization in this field. This will be achieved by presenting case studies, examining the diverse range of organisms that have been studied, and evaluating the potential benefits and drawbacks associated with the utilization of these methodologies. The utilization of advanced high-throughput bioinformatics techniques represents a sophisticated approach that necessitates a significant departure from the conventional practices of contemporary freshwater biomonitoring. The significant contributions of omics techniques in the context of biological quality elements (BQEs) and their interpretations in ecological problems are crucial for biomonitoring programs. Such contributions are primarily attributed to the previously overlooked identification of interactions between different levels of biological organization and their responses, isolated and combined, to specific critical conditions.

DNA barcoding of the genus Alburnoides Jeitteles, 1861 (Actinopterygii, Cyprinidae) from Anatolia, Turkey

The present study investigated the ability of DNA barcoding to reliably identify the endemic freshwater species in Turkey, known as biodiversity hotspots. The barcode region (652 bp) of the mitochondrial cytochrome c oxidase subunit I (COI) was used to barcode 153 individuals from 13 morphologically identified species of the genus Alburnoides. Based on the Kimura two-parameter (K2P) evolution model, the average interspecific distance (0.0595) was 31-fold higher than the average intraspecific distance (0.0019). There was a clear-cut barcode gap (0.0158–0.0187) between maximum intraspecific distance (A. tzanevi and A. velioglui) and minimum nearest-neighbour distance (A. freyhofi and A. kurui) for Anatolian Alburnoides species and a common genetic threshold of 0.0158 sequence divergence was defined for species delimitation. The multiple species delimitation methods (ABGD, ASAP, GMYC and bPTP) revealed a total of 11 molecular operational taxonomic units (MOTUs) for 13 morphospecies. Neighbour-joining (NJ), Maximum Likelihood (ML) and Bayesian Inference (BI) tree analysis indicated that all haplotypes were clustered into two major clades, which corresponded to eleven Alburnoides species clusters, with strong bootstrap support. Furthermore, all the specimens clustered in concurrence with the morpho-taxonomic status of the species, except for two species (A. coskuncelebii and A. emineae) that were morphologically differentiated, but showed overlap in variation for COI-based DNA barcode data with other species. Overall, present results identified that COI-based DNA barcoding is effective for species identification and cataloguing of genus Alburnoides in Turkey.

Ecological and morphological differentiation among COI haplotype groups in the plant parasitic nematode species Mesocriconema xenoplax

DNA barcoding with the mitochondrial COI gene reveals distinct haplotype subgroups within the monophyletic and parthenogenetic nematode species, Mesocriconema xenoplax. Biological attributes of these haplotype groups (HG) have not been explored. An analysis of M. xenoplax from 40 North American sites representing both native plant communities and agroecosystems was conducted to identify possible subgroup associations with ecological, physiological, or geographic factors. A dataset of 132 M. xenoplax specimens was used to generate sequences of a 712 bp region of the cytochrome oxidase subunit I gene. Maximum-likelihood and Bayesian phylogenies recognized seven COI HG (≥99/0.99 posterior probability/bootstrap value). Species delimitation metrics largely supported the genetic integrity of the HG. Discriminant function analysis of HG morphological traits identified stylet length, total body length, and stylet knob width as the strongest distinguishing features among the seven groups, with stylet length as the strongest single distinguishing morphological feature. Multivariate analysis identified land cover, ecoregion, and maximum temperature as predictors of 53.6% of the total variation (P = 0.001). Within land cover, HG categorized under “herbaceous,” “woody wetlands,” and “deciduous forest” were distinct in DAPC and RDA analyses and were significantly different (analysis of molecular variance P = 0.001). These results provide empirical evidence for molecular, morphological, and ecological differentiation associated with HG within the monophyletic clade that represents the species Mesocriconema xenoplax.

Identifying the Genetic Distance Threshold for Entiminae (Coleoptera: Curculionidae) Species Delimitation via COI Barcodes

The subfamily Entiminae is the largest group in the family Curculionidae, and it has long represented a challenge in traditional and molecular classification. Here, we analyzed intra- and interspecific genetic distances of 621 public COI barcode sequences (658bp) from 39 genera and 110 species of Entiminae, to determine parameters most congruent in retaining established species. We found that the mean intraspecific genetic distance (3.07%) was much smaller than the mean interspecific one (21.96%), but there is a wide range of overlap between intra- and interspecific genetic distances (0.77−18.01%), indicating that there is no consistent, universal barcoding gap. Specifically, DNA barcoding gap analysis for morphospecies revealed that 102 of 110 morphospecies had barcoding gaps, and 9.18% was the optimum threshold of genetic distances for 97 species delimitation. We further confirmed this threshold with barcodes from 27 morphologically identified specimens (including 21 newly reported barcodes) sequenced from five genera and seven species. We also identified thresholds to delimit congeneric species within 14 selected genera (species > 2), which varied from 7.42% (Trichalophus) to 13.48% (Barypeithes). We herein present optimal parameters for species identification in the Entiminae. Our study suggests that despite no universal genetic distance threshold value in subfamily Entiminae, 9.18% is optimal for most species. We recommend a wider sampling of geographic populations to better account for intraspecific distance variation, and that genetic distance thresholds for species delimitation should be refined at the genus level.