Toward a global DNA barcode reference library of the intolerant nonbiting midge genus Rheocricotopus Brundin, 1956

Abstract

Environmental DNA metabarcoding is becoming a predominant tool in biodiversity assessment, as this time‐ and cost‐efficient tactics have the ability to increase monitoring accuracy. As a worldwide distributed genus, Rheocricotopus Brundin, 1956 still does not possess a complete and comprehensive global DNA barcode reference library for biodiversity monitoring. In the present study, we compiled a cytochrome c oxidase subunit 1 (COI) DNA barcode library of Rheocricotopus with 434 barcodes around the world, including 121 newly generated DNA barcodes of 32 morphospecies and 313 public barcodes. Automatic Barcode Gap Discovery (ABGD) was applied on the 434 COI barcodes to provide a comparison between the operational taxonomic units (OTU) number calculated from the Barcode Index Number (BIN) with the “Barcode Gap Analysis” and neighbor‐joining (NJ) tree analysis. Consequently, these 434 COI barcodes were clustered into 78 BINs, including 42 new BINs. ABGD yielded 51 OTUs with a prior intraspecific divergence of Pmax = 7.17%, while NJ tree revealed 52 well‐separated clades. Conservatively, 14 unknown species and one potential synonym were uncovered with reference to COI DNA barcodes. Besides, based on our ecological analysis, we discovered that annual mean temperature and annual precipitation could be considered as key factors associated with distribution of certain members from this genus. Our global DNA barcode reference library of Rheocricotopus provides one fundamental database for accurate species delimitation in Chironomidae taxonomy and facilitates the biodiversity monitoring of aquatic biota.

Mitochondrial DNA evidence reflects high genetic divergence of Amynthas aspergillum (Oligochaeta: Megascolecidae) in southern China

“…In particular, clade I had the greatest inter‐clade (9.43%–10.26%) and intra‐clade genetic divergence (0.76%), suggesting the existence of cryptic species. However, population size, rate of mutation and divergence time vary between species, a universal fixed distance threshold may not be applicable to all species (Lin et al., 2021; Yang & Rannala, 2017). Another more widely‐used and rigorous threshold for species delimitation is the “10× rule”—the mean interspecific distance is considered to be at least 10 times as large as the mean intraspecific distance (Hebert et al., 2004).…”

“…But the term barcode gap requires a more precise and statistically sound definition (Čandek & Kuntner, 2015). For species with deep intraspecific divergence, inadequate sampling, incomplete lineage sorting and gene flow may lead to incorrect species delimitation (Lin et al., 2021). Therefore, the final species delimitation requires further comprehensive validation from both morphological and molecular aspects, or even in combination of other types of information such as geography, behavior, and ecological preferences (Cheng et al., 2023).…”

DNA barcodes and morphology reveal new species within the Rheotanytarsus guineensis species group from China (Diptera: Chironomidae)

“…The DNA barcode, corresponding to the 658‐bp fragment of the 5′‐end of the mitochondrial gene cytochrome c oxidase I (COI), has been identified as the core of a global bio‐identification system at the species level and it has been considered the most commonly used marker for identifying nonbiting midge species delimitation (Hebert, Cywinska, et al, 2003; Hebert, Ratnasingham, et al, 2003). COI barcodes have provided important evidence to confirm new species (Anderson et al, 2013; Ekrem et al, 2018; Gadawski et al, 2022; Han et al, 2020, 2023; Kodama et al, 2018; Lin et al, 2015, 2018, 2019, 2020; Lin, Jiang, et al, 2021; Lin, Mo, et al, 2021; Lin et al, 2021; Song et al, 2018; Stur et al, 2019). In the R. guineensis group, DNA barcodes for only one species ( Rheotanytarsus ringei Lehmann, 1970) were reported in past studies.…”