New records of immature aquatic Diptera from the Foulden Maar Fossil-Lagerstätte, New Zealand, and their biogeographic implications

Background

The biogeographical and ecological history of true flies (Diptera) in New Zealand is little known due to a scarcity of fossil specimens. Here, we report a fauna of immature aquatic dipterans from freshwater diatomites of the early Miocene Foulden Maar Fossil-Lagerstätte in southern New Zealand.

Methods

We document 30 specimens of immature dipterans, mostly pupae, and compare their external morphology to extant aquatic Diptera. Based on the reconstructed paleoenvironment of Foulden Maar, we discuss taxonomic, ecological and taphonomic implications of this early Miocene fauna.

Results

Among Chironomidae, one pupal morphotype is attributed to Tanypodinae, one pupal morphotype and one larval morphotype are placed into Chironomus (Chironominae) and a further morphotype into Chironominae incertae sedis. Chaoboridae are represented by a pupal morphotype congeneric or very close to the extant Chaoborus, today globally distributed except for New Zealand. Additional immature specimens are likely larvae and puparia of brachyceran flies but cannot be identified to a narrower range. These finds document an aquatic dipteran fauna in New Zealand in the earliest Miocene and highlight Neogene extinction as a factor in shaping the extant Diptera fauna in New Zealand. Immature aquatic dipterans were a common and likely ecologically important component of the early Miocene Foulden Maar lake. Preservation of larvae and pupae may have been promoted by diatomaceous microbial mats and the light colour of the diatomite likely facilitated spotting of these minute fossils in the field.

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

The Rheotanytarsus guineensis species group (Diptera: Chironomidae) is a species diverse and taxonomically difficult group. Using DNA barcodes, we found five new species within the R. guineensis species group and reviewed the species group based on adult males from China. Rheotanytarsus guoae Lin & Yao sp. n., Rheotanytarsus miaoae Lin & Yao sp. n., Rheotanytarsus qiangi Lin & Yao sp. n., Rheotanytarsus yueqingensis Lin & Yao sp. n., and Rheotanytarsus yui Lin & Yao sp. n. are all described and figured. A key to known adult males of the R. guineensis species group worldwide is provided for the first time.

Connecting the dots: DNA barcoding and lectotype designation shedding light on Labrundinia longipalpis (Goetghebuer, 1921), an intriguing non-biting midge (Chironomidae, Tanypodinae)

Accurate taxonomic classification is deemed paramount for gaining an understanding of the diversity and distribution of insect species. In this study, an essential stride was made towards advancing the taxonomy of the non-biting midge Labrundinia longipalpis (Chironomidae, Tanypodinae), which serves as the type species of the genus. The distribution of L. longipalpis is particularly intriguing as it contrasts with the predominantly tropical distribution of the genus, with this species being found across the Holarctic region. The main goal of this investigation was to designate a lectotype and several paralectotypes, which was achieved through a comprehensive reexamination of the original material, alongside additional specimens obtained from the type-locality in Flanders. Furthermore, the distribution of L. longipalpis across Europe and North America was examined, and the proposed synonymization of L. maculata with the latter was challenged using the analysis of molecular data. Through the comparison of DNA barcodes, it was revealed that the North American population of L. longipalpis clustered together with the European population, which alludes to a considerable level of genetic similarity between these two populations. These results provide valuable insights into the behavior, ecological dynamics and biogeography of L. longipalpis, while also raising interesting questions about colonization and distribution patterns attributed to its adaptability and potential for long-distance dispersal.

A DNA barcode survey of insect biodiversity in Pakistan

Although Pakistan has rich biodiversity, many groups are poorly known, particularly insects. To address this gap, we employed DNA barcoding to survey its insect diversity. Specimens obtained through diverse collecting methods at 1,858 sites across Pakistan from 2010-2019 were examined for sequence variation in the 658 bp barcode region of the cytochrome c oxidase 1 (COI) gene. Sequences from nearly 49,000 specimens were assigned to 6,590 Barcode Index Numbers (BINs), a proxy for species, and most (88%) also possessed a representative image on the Barcode of Life Data System (BOLD). By coupling morphological inspections with barcode matches on BOLD, every BIN was assigned to an order (19) and most (99.8%) were placed to a family (362). However, just 40% of the BINs were assigned to a genus (1,375) and 21% to a species (1,364). Five orders (Coleoptera, Diptera, Hemiptera, Hymenoptera, Lepidoptera) accounted for 92% of the specimens and BINs. More than half of the BINs (59%) are so far only known from Pakistan, but others have also been reported from Bangladesh (13%), India (12%), and China (8%). Representing the first DNA barcode survey of the insect fauna in any South Asian country, this study provides the foundation for a complete inventory of the insect fauna in Pakistan while also contributing to the global DNA barcode reference library.

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

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.

The importance of DNA barcode choice in biogeographic analyses - a case study on marine midges of the genus Clunio

DNA barcodes are widely used for species identification and biogeographic studies. Here, we compare the use of full mitochondrial genomes versus DNA barcodes and other mitochondrial DNA fragments for biogeographic and ecological analyses. Our dataset comprised 120 mitochondrial genomes from the genus Clunio (Diptera: Chironomidae), comprising five populations from two closely related species (Clunio marinus and Clunio balticus) and three ecotypes. We extracted cytochrome oxidase c subunit I (COI) barcodes and partitioned the mitochondrial genomes into non-overlapping windows of 750 or 1500 bp. Haplotype networks and diversity indices were compared for these windows and full mitochondrial genomes (15.4 kb). Full mitochondrial genomes indicate complete geographic isolation between populations, but do not allow for conclusions on the separation of ecotypes or species. COI barcodes have comparatively few polymorphisms, ideal for species identification, but do not resolve geographic isolation. Many of the similarly sized 750 bp windows have higher nucleotide and haplotype diversity than COI barcodes, but still do not resolve biogeography. Only when increasing the window size to 1500 bp, two windows resolve biogeography reasonably well. Our results suggest that the design and use of DNA barcodes in biogeographic studies must be carefully evaluated for each investigated species.

Back from the Past: DNA Barcodes and Morphology Support Ablabesmyia americana Fittkau as a Valid Species (Diptera: Chironomidae)

Short, standardized gene fragments for species identification (DNA barcodes) have proven effective in delineating closely-related insect species, and can be critical characters to include in taxonomic studies. This is also the case for the species-rich and widely distributed fly family Chironomidae (non-biting midges). Inspired by observed genetic differences in partial COI gene sequences between North American and European populations of the chironomid Ablabesmyia monilis sensu lato, we investigated whether or not the morphology of male and female adults supported the distinction of more than one species. Our results support that the junior synonym Ablabesmyia americana is a valid species separate from A. monilis, and that A. monilis sensu stricto is distributed both in the Palearctic region and in North America. We provide re-descriptions of all of the major life stages of A. americana and of the adult female of A. monilis.