Complete mitochondrial genome of Skylark, Alauda arvensis (Aves: Passeriformes): the first representative of the family Alaudidae with two extensive heteroplasmic control regions

Selected Lark Mitochondrial Genomes Provide Insights into the Evolution of Second Control Region with Tandem Repeats in Alaudidae (Aves, Passeriformes)

The control region (CR) regulates the replication and transcription of the mitochondrial genome (mitogenome). Some avian mitogenomes possess two CRs, and the second control region (CR2) may enhance replication and transcription; however, the CR2 in lark mitogenome appears to be undergoing loss and is accompanied by tandem repeats. Here, we characterized six lark mitogenomes from Alaudala cheleensis, Eremophila alpestris, Alauda razae, and Calandrella cinerea and reconstructed the phylogeny of Passerida. Through further comparative analysis among larks, we traced the evolutionary process of CR2. The mitochondrial gene orders were conserved in all published lark mitogenomes, with Cytb-trnT-CR1-trnP-ND6-trnE-remnant CR2 with tandem repeat-trnF-rrnS. Phylogenetic analysis revealed Alaudidae and Panuridae are sister groups at the base of Sylvioidea, and sporadic losses of CR2 may occur in their common ancestor. CR sequence and phylogeny analysis indicated CR2 tandem repeats were generated within CR2, originating in the ancestor of all larks, rather than inherited from CR1. The secondary structure comparison of tandem repeat units within and between species suggested slipped-strand mispairing and DNA turnover as suitable models for explaining the origin and evolution of these repeats. This study reveals the evolutionary process of the CR2 containing tandem repeat in Alaudidae, providing reference for understanding the evolutionary characteristics and dynamics of tandem repeats.

Identification and phylogenetic analysis in Pterorhinuschinensis (Aves, Passeriformes, Leiothrichidae) based on complete mitogenome

The Black-throated Laughingthrush (Pterorhinuschinensis) is a bird belonging to the order Passeriformes and the family Leiothrichidae, and is found in Cambodia, China, Laos, Myanmar, Thailand and Vietnam. Pterorhinuschinensis was once classified as belonging to the genus Garrulax. However, recent research has reclassified it in the genus Pterorhinus. In this study, we sequenced and characterized the complete mitogenome of P.chinensis. The complete mitochondrial genome of P.chinensis is 17,827 bp in length. It consists of 13 PCGs, 22 tRNAs, two rRNAs, and two control regions. All genes are coded on the H-strand, except for one PCG (nad6) and eight tRNAs. All PCGs are initiated with ATG and stopped by five types of stop codons. Our comparative analyses show irregular gene rearrangement between trnT and trnP genes with another similar control region emerging between trnE and trnF genes compared with the ancestral mitochondrial gene order, called "duplicate CR gene order". The phylogenetic position of P.chinensis and phylogenetic relationships among members of Leiothrichidae are assessed based on complete mitogenomes. Phylogenetic relationships based on Bayesian inference and maximum likelihood methods showed that Garrulax and (Pterorhinus + Ianthocincla) formed a clade. Leiothrix and Liocichla also formed a clade. Our study provides support for the transfer of P.chinensis from Garrulax to Pterorhinus. Our results provide mitochondrial genome data to further understand the mitochondrial genome characteristics and taxonomic status of Leiothrichidae.

The complete mitochondrial genome and the phylogenetic position of Alauda gulgula (Aves: Passeriformes)

The Oriental Skylark (Alauda gulgula) is a small songbird in the Alaudidae. Here we assembled the complete mitochondrial genome of Alauda gulgula which is 17,055 bp in length and consisting of 13 protein-coding genes (PCGs), 2 ribosomal RNA, 22 transfer RNA, and 2 extensive heteroplasmic control regions. The overall A + T content of the mitogenome is 52.3%The maximum-likelihood (ML) tree based on the complete mitochondrial genome of A. gulgula revealed the close genetic relationship between A. gulgula and A. arvensis, but separate from A. cheleensis.

New view on the organization and evolution of Palaeognathae mitogenomes poses the question on the ancestral gene rearrangement in Aves

BACKGROUND

Bird mitogenomes differ from other vertebrates in gene rearrangement. The most common avian gene order, identified first in Gallus gallus, is considered ancestral for all Aves. However, other rearrangements including a duplicated control region and neighboring genes have been reported in many representatives of avian orders. The repeated regions can be easily overlooked due to inappropriate DNA amplification or genome sequencing. This raises a question about the actual prevalence of mitogenomic duplications and the validity of the current view on the avian mitogenome evolution. In this context, Palaeognathae is especially interesting because is sister to all other living birds, i.e. Neognathae. So far, a unique duplicated region has been found in one palaeognath mitogenome, that of Eudromia elegans.

RESULTS

Therefore, we applied an appropriate PCR strategy to look for omitted duplications in other palaeognaths. The analyses revealed the duplicated control regions with adjacent genes in Crypturellus, Rhea and Struthio as well as ND6 pseudogene in three moas. The copies are very similar and were subjected to concerted evolution. Mapping the presence and absence of duplication onto the Palaeognathae phylogeny indicates that the duplication was an ancestral state for this avian group. This feature was inherited by early diverged lineages and lost two times in others. Comparison of incongruent phylogenetic trees based on mitochondrial and nuclear sequences showed that two variants of mitogenomes could exist in the evolution of palaeognaths. Data collected for other avian mitogenomes revealed that the last common ancestor of all birds and early diverging lineages of Neoaves could also possess the mitogenomic duplication.

CONCLUSIONS

The duplicated control regions with adjacent genes are more common in avian mitochondrial genomes than it was previously thought. These two regions could increase effectiveness of replication and transcription as well as the number of replicating mitogenomes per organelle. In consequence, energy production by mitochondria may be also more efficient. However, further physiological and molecular analyses are necessary to assess the potential selective advantages of the mitogenome duplications.

Molecular Species Delimitation of Larks (Aves: Alaudidae), and Integrative Taxonomy of the Genus Calandrella, with the Description of a Range-Restricted African Relic Taxon

Larks constitute an avian family of exceptional cryptic diversity and striking examples of convergent evolution. Therefore, traditional morphology-based taxonomy has recurrently failed to reflect evolutionary relationships. While taxonomy ideally should integrate morphology, vocalizations, behaviour, ecology, and genetics, this can be challenging for groups that span several continents including areas that are difficult to access. Here, we combine morphometrics and mitochondrial DNA to evaluate the taxonomy of Calandrella larks, with particular focus on the African C. cinerea and the Asian C. acutirostris complexes. We describe a new range-restricted West African taxon, Calandrella cinerea rufipecta ssp. nov. (type locality: Jos, Plateau State, Nigeria), with an isolated relic population 3000 km from its closest relative in the Rift Valley. We performed molecular species delimitation, employing coalescence-based multi-rate Poisson Tree Processes (mPTP) on cytochrome b sequences across 52 currently recognized lark species, including multiple taxa currently treated as subspecies. Three species-level splits were inferred within the genus Calandrella and another 13 across other genera, primarily among fragmented sub-Saharan taxa and taxa distributed from Northwest Africa to Arabia or East Africa. Previously unknown divergences date back as far as to the Miocene, indicating the presence of currently unrecognized species. However, we stress that taxonomic decisions should not be based on single datasets, such as mitochondrial DNA, although analyses of mitochondrial DNA can be a good indicator of taxa in need of further integrative taxonomic assessment.

The complete mitochondrial genomes of Tarsiger cyanurus and Phoenicurus auroreus: a phylogenetic analysis of Passeriformes

Passeriformes is the largest group within aves and the phylogenetic relationships between Passeriformes have caused major disagreement in ornithology. Particularly, the phylogenetic relationships between muscicapoidea and sylvioidea are complex, and their taxonomic boundaries have not been clearly defined. Our aim was to study the status of two bird species: Tarsiger cyanurus and Phoenicurus auroreus. Furthermore, we analyzed the phylogenetic relationships of Passeriformes. Complete mitochondrial DNA (mtDNA) sequences of both species were determined and the lengths were 16,803 (T. cyanurus) and 16,772 bp (P. auroreus), respectively. Thirteen protein-coding genes, 22 tRNA genes, two rRNA genes, and one control region were identified in these mtDNAs. The contents of A and T at the base compositions was significantly higher than the content of G and C, and this AT skew was positive, while the GC skew was negative. The monophyly of Passeriformes is divided into four major clades: Corvoidea, Sylvioidea, Passeroidea, and Musicicapoidea. Paridae should be separated from the superfamily Sylvioidea and placed within the superfamily Muscicapoidea. The family Muscicapidae and Corvida were paraphyly, while Carduelis and Emberiza were grouped as a sister taxon. The relationships between some species of the order passeriformes may remain difficult to resolve despite an effort to collect additional characters for phylogenetic analysis. Current research of avian phylogeny should focus on adding characters and taxa and use both effectively to obtain a better resolution for deeper and shallow nodes.

Complete mitochondrial genome of the Mongolian lark, Melanocorypha mongolica (Aves: Passeriformes)

We sequenced the entire mitochondrial genome of Melanocorypha mongolica for the first time. The mitogenome is 17,358 bp in length, which includes 13 protein-coding genes, 22 tRNA genes, 2 ribosomal RNA (rRNA) genes, the control region (CR1), and the control region 2 (CR2). Gene order follows a pattern similar to those of Eurasian Skylark. Using mitochondrial genomes of Melanocorypha mongolica and other seven reference birds in Sylvioidea, we preformed Bayesian analysis based on concatenated protein-coding genes. The results reveal that Alaudidae and Acroccphalidae are clustered together, which is sister to the branches included Sylviidae and Leiothrichidae. Further sequencing of mitochondrial genomes in Alaudidae is useful to advance phylogenetic relationship of species in the family.

Complete mitochondrial genome sequence of Garrulax formosus (Aves, Passeriformes, Timaliidae) and its phylogenetic analysis

The complete mitochondrial genome of Garrulax formosus was obtained for the first time, which is 17 869 bp in length and contains 13 protein-coding genes (PCGs), 2 rRNA, 22 tRNA genes and 2 different control regions. All genes are distributed in plus strand, with the exceptions of one PCG (ND6) and eight tRNA genes. All PCGs are initiated with ATG, except for COX1, which is initiated with GTG, while stopped by five types of stop codons. All tRNA genes have the potential to fold into typical clover-leaf structure except tRNA(Ser)(GCT). According to the phylogenetic tree, we can infer that it is reasonable to divide Garrulax formosus into the genus Garrulax.

The complete mitochondrial genome sequence of Garrulax ocellatus (Aves, Passeriformes, Timaliidae)

Timaliidae, generally known as the babblers, includes about 275 species in 50 genera. We sequenced the complete mitochondrial genome of Garrulax ocellatus, and it was determined to be 17,828 bp in length, containing 13 protein-coding genes (PCGs), 2 rRNA genes, 22 tRNAsfer (tRNA) genes, and 2 control regions. The complete mitochondrial genome contained 15.24% G, 23.02% T, 33.13% C, and 28.61% A, which was similar to other Passeriformes mitochondrial genomes. There are eight tRNA genes and one PCG (ND6) encoded on the L-strand, and other PCGs were encoded on the H-strand. All genes were closely assembled and only 17 intergenic spacers were observed. In total, the spacers were 99 bp in length, and there were seven pairs of genes overlapping sequences of 30 bp in length. Phylogenetic relationship could provide useful information for the further study on the species taxonomic.

Complete mitochondrial genome of the Eurasian siskin, Spinus spinus (Passeriformes: Fringillidae)

The Eurasian siskin (Spinus spinus), also called the European siskin, common siskin or just siskin, is found throughout Europe and Asia. In this study, the complete mitochondrial genome of S. spinus was determined to be 16,828 bp. The size of protein-coding genes (PCGs) in the S. spinus mitochondrial genome was 11,400 bp. The longest PCG of S. spinus mtDNA was nad5 (1818 bp), whereas the shortest is atp8 (168 bp). The nad6 gene of S. spinus mitogenome had strong skews of T versus A (-0.54), and G versus C (0.64). According to the distribution of the conserved motifs in other avian CRs, the CR of S. spinus can be divided into three domains: ETAS domain I, central conserved domain II, and CSB domain III.

Characterization of the complete mitochondrial genome of Collared Finchbill, Spizixos semitorques (Passeriformes: Pycnonotidae)

The complete mitochondrial genome of Spizixos semitorques is 17,045 bp long with an A+T content of 55.52%, which composed of 13 typical protein-coding genes, 22 transfer RNA (tRNA) genes, 2 ribosomal RNA (rRNA) genes, and 2 extensive heteroplasmic control regions (CR1 and CR2). Genome organization of S. semitorques is similar to that of other birds. All of the PCGs started with ATG, except for cox1, which began with GTG. Six types of termination codons were used, canonical TAA and TAG termination codons are found in seven protein-coding genes, while AGA for nad1 and nad5, AGG for cox1, and the remaining genes (nad2, cox3, nad4) have incomplete termination codons (TA- or T- -). All tRNA genes have a typical clover-leaf structure. Furthermore, a minisatellite of 24 nucleotides (5'-CACAAAAATCAAACAAAAATACAA-3') with 2.9 tandem repeats at the end of CR2 were detected.