The mitochondrial genome of the Kentish Plover Charadrius alexandrinus (Charadriiformes: Charadriidae) and phylogenetic analysis of Charadrii

Complete Mitochondrial Genomes of Pluvialis fulva and Charadrius dubius with Phylogenetic Analysis of Charadriiformes

BACKGROUND

Plovers (Charadriidae), within the order of Charadriiformes, a group of modern birds distributed worldwide, are a frequent subject of molecular phylogenetic studies. While research on mitochondrial genome (mitogenome) variation within the family Charadriidae, especially intraspecific variation, is limited. Additionally, the monophyly of Charadrius and the phylogenetic placement of Pluvialis remain contentious. Nevertheless, recent studies utilizing complete mitogenomes from available databases to construct phylogenetic trees for Charadriidae and Charadriiformes remain scarce.

METHODS

This study aims to explore mitogenome variation within Charadrius dubius and clarify the phylogenetic placement of Pluvialis fulva. We sequenced the complete mitogenome of six C. dubius and one P. fulva, and all additional available mitogenomes were integrated within Charadriiformes. The average complete mitogenome length of C. dubius is 16,889 bp, and P. fulva is 16,859 bp.

RESULTS

Our results support the suggestion that the monophyly of Charadrius and P. fulva is nested within Charadriidae. The phylogenetic analysis of Charadriiformes based on mitogenomes strongly supports the recognition of three major shorebird clades: Charadrii, Lari and Scolopaci, with Lari and Scolopaci identified as sister clades.

CONCLUSIONS

Our study reinforces the credibility of the inferred evolutionary relationships within Charadriidae and Charadriiformes.

Mitochondrial genome of the Indian spot-billed duck and its phylogenetic and conservation implications

The Indian spot-billed duck, Anas poecilorhyncha is a large dabbling and non-migratory breeding bird. The identification and phylogenetic relationship of A. poecilorhyncha remain uncertain due to the presence of overlapping meristic characters and hybridization with closely related species. Molecular data aids when there are challenges in morphological identification. However, genetic characterization of A. poecilorhyncha has been paid less attention. Apart from their functional and physiological role, mitochondrial genome can also be used for various purposes, including species identification, phylogenetic analysis, understanding the domestication history of species etc. Therefore, the present study aimed to sequence the mitochondrial genome of A. poecilorhyncha and its closely related domestic species A. platyrhynchos (mallard duck) to understand their mitochondrial genome structure and phylogenetic relationships. The length of mitochondrial genome of A. poecilorhyncha and A. platyrhynchos was 16,608 and 16,604 bp respectively. Mitochondrial genome contained 37 genes and a non-coding control region. Overall, the characteristics of mitochondrial genome of both species were found to be conserved. The phylogenetic tree exhibited seven major clades (A to G) with a high bootstrap support. Notably, the Indian A. poecilorhyncha population formed a distinct clade (C) whereas the A. poecilorhyncha that were probably sampled from China grouped along with A. zonorhyncha (clade B). Besides, one of the A. poecilorhyncha probably sampled from China was placed in the clade A, which predominantly consisted of A. platyrhynchos. It suggests that Indian A. poecilorhyncha population is genetically different from Chinese A. poecilorhyncha population. Further, it sheds light on the importance of conducting a comprehensive phylogenetic study on these species. The newly sequenced mitochondrial genome of A. poecilorhyncha and A. platyrhynchos would be useful not only to have a better understanding of the phylogeny and evolution of Anas species but also to help in the conservation of A. poecilorhyncha which is under constant threat from rapid urbanization, interspecific hybridization and other human activities.

Mitogenomic Insights into the Evolution, Divergence Time, and Ancestral Ranges of Coturnix Quails

The Old-World quails, Coturnix coturnix (common quail) and Coturnix japonica (Japanese quail), are morphologically similar yet occupy distinct geographic ranges. This study aimed to elucidate their evolutionary trajectory and ancestral distribution patterns through a thorough analysis of their mitochondrial genomes. Mitogenomic analysis revealed high structural conservation, identical translational mechanisms, and similar evolutionary pressures in both species. Selection analysis revealed significant evidence of positive selection across the Coturnix lineage for the nad4 gene tree owing to environmental changes and acclimatization requirements during its evolutionary history. Divergence time estimations imply that diversification among Coturnix species occurred in the mid-Miocene (13.89 Ma), and their current distributions were primarily shaped by dispersal rather than global vicariance events. Phylogenetic analysis indicates a close relationship between C. coturnix and C. japonica, with divergence estimated at 2.25 Ma during the Pleistocene epoch. Ancestral range reconstructions indicate that the ancestors of the Coturnix clade were distributed over the Oriental region. C. coturnix subsequently dispersed to Eurasia and Africa, and C. japonica to eastern Asia. We hypothesize that the current geographic distributions of C. coturnix and C. japonica result from their unique dispersal strategies, developed to evade interspecific territoriality and influenced by the Tibetan Plateau's geographic constraints. This study advances our understanding of the biogeographic and evolutionary processes leading to the diversification of C. coturnix and C. japonica, laying important groundwork for further research on this genus.

Complete mitochondrial genome MK992912 of Great Knot (Calidris tenuirostris) is a chimera with DNA from Pacific Golden Plover Pluvialis fulva (Aves: Charadriiformes)

A complete mitochondrial genome of Great Knot (Calidris tenuirostris), MK992912, was published by He and colleagues in 2020. Here we show that this mitogenome is actually a chimera containing DNA fragments of both C. tenuirostris (15,567 bp, 92.8%) and Pacific Golden Plover (Pluvialis fulva, 1208 bp, 7.2%). Detecting such errors is possible before publication if each sequenced fragment is separately analyzed phylogenetically before assembling the fragments into a single mitogenome. This mitogenome has been re-used in at least four phylogenies. The error is documented to avoid the perpetuation of erroneous sequence information in the literature.

Comparative mitogenomic and evolutionary analysis of Lycaenidae (Insecta: Lepidoptera): Potential association with high-altitude adaptation

Harsh environments (e.g., hypoxia and cold temperatures) of the Qinghai-Tibetan Plateau have a substantial influence on adaptive evolution in various species. Some species in Lycaenidae, a large and widely distributed family of butterflies, are adapted to the Qinghai-Tibetan Plateau. Here, we sequenced four mitogenomes of two lycaenid species in the Qinghai-Tibetan Plateau and performed a detailed comparative mitogenomic analysis including nine other lycaenid mitogenomes (nine species) to explore the molecular basis of high-altitude adaptation. Based on mitogenomic data, Bayesian inference, and maximum likelihood methods, we recovered a lycaenid phylogeny of [Curetinae + (Aphnaeinae + (Lycaeninae + (Theclinae + Polyommatinae)))]. The gene content, gene arrangement, base composition, codon usage, and transfer RNA genes (sequence and structure) were highly conserved within Lycaenidae. TrnS1 not only lacked the dihydrouridine arm but also showed anticodon and copy number diversity. The ratios of non-synonymous substitutions to synonymous substitutions of 13 protein-coding genes (PCGs) were less than 1.0, indicating that all PCGs evolved under purifying selection. However, signals of positive selection were detected in cox1 in the two Qinghai-Tibetan Plateau lycaenid species, indicating that this gene may be associated with high-altitude adaptation. Three large non-coding regions, i.e., rrnS-trnM (control region), trnQ-nad2, and trnS2-nad1, were found in the mitogenomes of all lycaenid species. Conserved motifs in three non-coding regions (trnE-trnF, trnS1-trnE, and trnP-nad6) and long sequences in two non-coding regions (nad6-cob and cob-trnS2) were detected in the Qinghai-Tibetan Plateau lycaenid species, suggesting that these non-coding regions were involved in high-altitude adaptation. In addition to the characterization of Lycaenidae mitogenomes, this study highlights the importance of both PCGs and non-coding regions in high-altitude adaptation.

Complete mitochondrial genome of little ringed plover Charadrius dubius (Charadriiformes, Charadriidae)

This study encoded the complete mitochondrial genomic sequence of the little ringed plover Charadrius dubius. The mitochondrial genome has a total length of 16,864 bp, consisting of 13 protein-coding genes, 22 tRNA genes, two rRNA genes, and a control region. The nucleotide composition was 23.8% T, 31.6% A, 30.8% C, and 13.8% G. This study provides the basic information on the mitogenome of C. dubius and supports the understanding of mitogenomic information and its phylogenetic relationship within Charadriiformes.

Comprehensive taxon sampling and vetted fossils help clarify the time tree of shorebirds (Aves, Charadriiformes)

Shorebirds (Charadriiformes) are a globally distributed clade of modern birds and, due to their ecological and morphological disparity, a frequent subject of comparative studies. While molecular phylogenies have been key to establishing the suprafamilial backbone of the charadriiform tree, a number of relationships at both deep and shallow taxonomic levels remain poorly resolved. The timescale of shorebird evolution also remains uncertain as a result of extensive disagreements among the published divergence dating studies, stemming largely from different choices of fossil calibrations. Here, we present the most comprehensive non-supertree phylogeny of shorebirds to date, based on a total-evidence dataset comprising 353 ingroup taxa (90% of all extant or recently extinct species), 27 loci (15 mitochondrial and 12 nuclear), and 69 morphological characters. We further clarify the timeline of charadriiform evolution by time-scaling this phylogeny using a set of 14 up-to-date and thoroughly vetted fossil calibrations. In addition, we assemble a taxonomically restricted 100-locus dataset specifically designed to resolve outstanding problems in higher-level charadriiform phylogeny. In terms of tree topology, our results are largely congruent with previous studies but indicate that some of the conflicts among earlier analyses reflect a genuine signal of pervasive gene tree discordance. Monophyly of the plovers (Charadriidae), the position of the ibisbill (Ibidorhyncha), and the relationships among the five subfamilies of the gulls (Laridae) could not be resolved even with greatly increased locus and taxon sampling. Moreover, several localized regions of uncertainty persist in shallower parts of the tree, including the interrelationships of the true auks (Alcinae) and anarhynchine plovers. Our node-dating and macroevolutionary rate analyses find support for a Paleocene origin of crown-group shorebirds, as well as exceptionally rapid recent radiations of Old World oystercatchers (Haematopodidae) and select genera of gulls. Our study underscores the challenges involved in estimating a comprehensively sampled and carefully calibrated time tree for a diverse avian clade, and highlights areas in need of further research.

Analysis of the mitochondrial genome of the Indian darter, Anhinga melanogaster, suggests a species status taxonomic rank

BACKGROUND

Anhinga melanogaster is a carnivorous water bird native to many Asian countries. A. melanogaster is part of the Old World clade of darters. There is currently significant debate about the organization of the Old World clade due to morphological and genetic ambiguities. It is essential to establish the taxonomic status of A. melanogaster because it was recently listed by the International Union for Conservation of Nature (IUCN) as a near threatened species.

METHODS AND RESULTS

The present study utilized a comprehensive molecular approach of the complete mitogenome of A. melanogaster to resolve its taxonomic status within the genus Anhinga. The mitogenome of A. melanogaster comprised of 13 protein-coding genes, 22 tRNA genes, 2 rRNA genes and a control region. A partially duplicated cytochrome b gene and control region were also present.

CONCLUSIONS

Duplicated mitogenomic segments and phylogenetic analyses suggest that A. melanogaster, A. novaehollandiae, A. rufa and A. anhinga should be considered distinct species within the Old World clade of darters. The present study provides new insights into the mitogenome features of A. melanogaster and its evolutionary relationship within the genus, Anhinga.

The complete mitochondrial genome of Lesser Sand-Plover Charadrius mongolus atrifrons and its phylogenetic position

The Lesser Sand-Plover (Charadrius mongolus atrifrons) is a small shorebird in Charadriiformes. Here we assembled the complete mitochondrial genome of C. m. atrifrons (Aves: Charadriiformes) which is 16,919 bp in length and consisting of 13 protein-coding (PCGs), 2 ribosomal RNA, 22 transfer RNA and 1 control region. The overall A + T content of was 55.5%. The Maximum Likelihood (ML) tree based on the 12 concatenated mitochondrial protein-coding genes (except ND6 gene) placed C. m. atrifrons in a clade with C. alexandrines but separate from C. vociferus.

Sharp Increase of Problematic Mitogenomes of Birds: Causes, Consequences, and Remedies

Authentic DNA sequences are crucial for reliable evolutionary inference. Concerns about the identification of DNA sequences have been voiced several times in the past but few quantitative studies exist. Mitogenomes play important roles in phylogenetics, phylogeography, population genetics, and DNA identification. However, the large number of mitogenomes being published routinely, often in brief data papers, has raised questions about their authenticity. In this study, we quantify problematic mitogenomes of birds and their reusage in other papers. Of 1,876 complete or partial mitogenomes of birds published until January 1, 2020, the authenticity of 1,559 could be assessed with sequences of conspecifics. Of these, 78 (5.0%) were found to be problematic, including 45 curated reference sequences. Problems were due to misidentification (33), chimeras of two or three species (23), sequencing errors/numts (18), incorrect sequence assembly (1), mislabeling at GenBank but not in the final paper (2), or vice versa (1). The number of problematic mitogenomes has increased sharply since 2012. Worryingly, these problematic sequences have been reused 436 times in other papers, including 385 times in phylogenies. No less than 53% of all mitogenomic phylogenies/networks published until January 1, 2020 included at least one problematic mitogenome. Problematic mitogenomes have resulted in incorrect phylogenetic hypotheses and proposals for unwarranted taxonomic revision, and may have compromised comparative analyses and measurements of divergence times. Our results indicate that a major upgrade of quality control measures is warranted. We propose a comprehensive set of measures that may serve as a new standard for publishing mitogenome sequences.

Mercury exposure in sedentary and migratory Charadrius plovers distributed widely across China

Mercury pollution is a global problem and of particular concern in high emissions areas, such as China. We studied the migratory Kentish Plover, Charadrius alexandrinus, which breeds in coastal northern/central China and the inland Qinghai Lake, and the White-faced Plover C. dealbatus, a year-round resident of coastal southern China. We measured total mercury (THg) concentrations in feather and blood samples of breeding females. We expected low levels at the remote Qinghai Lake, but we found instead that feather THg concentrations were highest there (3.89 ± 1.53 [SD] μg/g DW [n = 34]; compared to 1.29 ± 0.61 μg/g of Kentish Plover elsewhere [n = 35] and 2.08 ± 1.45 μg/g for White-faced Plover [n = 56]), a result is consistent over 2 years. When including only coastal populations in the analysis, there were no differences in THg concentrations between the two species, although White-faced Plover had more variation. Feather THg concentrations for the coastal populations are similar to other studies on plovers and sandpipers globally, with most birds under the threshold of adverse effects (3 μg/g, an estimate that itself may be too low). Nevertheless, the Qinghai Kentish Plover population has mean feather concentrations above this threshold, indicating high exposure during the nonbreeding season, and some individuals have extreme values (e.g., a bird with a blood level of 7.63 μg/g DW from Zhanjiang, south China), so further research and monitoring are needed.