The complete mitochondrial genome of Ochetellus glaber (Mayr, 1862) (Hymenoptera:Formicidae).

Ochetellus glaber (Mayr, 1867) is a dolichoderine ant found in the warm regions of Asia and Australia. We have determined the mitochondrial genome of O. glaber whose length is 16,259 bp including 13 protein-coding genes, 2 ribosomal RNA genes, 22 transfer RNAs, and a single large control region. The base composition was AT-biased (GC ratio is 17.8%). Gene order of O. glaber is identical to other species of the subfamily Dolichoderinae. Phylogenetic trees show that O. glaber is nested in other mitochondrial genomes of tribe Leptomyrmecini, implying the neotropical genera are ancestral to Australian genera such as Ochetellus.

Ochetellus glaber, also known as the black household ant, is a minute ant found in the tropics and the subtropics of Asia and Australia (Janicki et al. 2016). It was first considered as an invasive species from Australia which spread out through human interactions. Further investigations on their morphologies, however, proved that O. glaber is a species complex indicating that the ants are, in fact, multiple species native to each region (Hoffmann et al. 2011). Still, boundaries between species are unclear and require additional in-depth investigations. As a first step in understanding the genetic background of this species, we successfully determined its complete mitochondrial genome.

Total DNA of O. glaber workers was extracted from the samples collected in Gageodo, Jeollanom-do, Republic of Korea (34°03′04.0″N; 125°07′48.0″E), using DNeasy Blood &Tissue Kit (QIAGEN, Hilden, Germany). Raw sequences obtained from Illumina HiSeqX at Macrogen Inc., Korea, were filtered by Trimmomatic 0.33 (Bolger et al. 2014) and de novo assembled and confirmed by Velvet 1.2.10 (Zerbino and Birney 2008), SOAPGapCloser 1.12 (Zhao Q-Y et al. 2011), BWA 0.7.17 (Li et al. 2009), and SAMtools 1.9 (Li 2013). Geneious R11 11.1.5 (Biomatters Ltd, Auckland, New Zealand) was used for annotation based on the other ant mitogenomes. ARWEN (Laslett and Canbäck 2008) was used to annotate tRNAs. DNA sample and specimen (95% ethanol) are deposited in the InfoBoss Cyber Herbarium (IN; J. Park, KFDS00124).

The mitochondrial genome of O. glaber (Genbank accession is MN044390) is 16,259 bp long and its GC ratio is 17.8%, which is the longest and most AT-biased Dolichoderine mitochondrial genome (Linepithema humile; 16,098 bp (Zhao E et al. 2017) and Dolichoderus sibiricus; 18.2% (Park et al. 2019)). It contains 13 protein-coding genes (PCGs), 2 rRNAs, 22 tRNAs, and a AT-rich control region. Gene order of O. glaber is identical to those of all other Dolichoderinae and closely related Pseudomyrmecinae (Vieira and Prosdocimi 2019). All PCGs start with typical ATN codon and end with a TAA or T– – except ND4L which stops with codon TAG.

Thirteen PCGs and two rRNA genes from 19 ants mitogenomes including all available Dolichoderine species and an outgroup species, Apis mellifera ligustica, were aligned by MAFFT 7.450 (Katoh and Standley 2013) each. Bootstrapped maximum likelihood (bootstrap repeat is 1,000), neighbor joining (bootstrap repeat is 10,000), and bayesian inference (1,100,000 generations) trees were constructed using MEGA X (Kumar et al. 2018) and Mr. Bayes 3.2.6 (Huelsenbeck and Ronquist 2001). Phylogenetic trees show that O. glaber is located inside tribe Leptomyrmecini clade (Figure 1), congruent with former evolutionary study presenting old-world Leptomyrmecini genera such as Ochetellus arose from neotropical groups of this tribe, such as Dorymyrmex, Linepithema, and Leptomyrmex (Ward et al. 2010). However, maximum likelihood tree displays that Leptomyrmex pallens (NC_023093) is not clustered with the rest of the tribemates, but the other two trees show that it is placed at correct position (Figure 1). All subfamilies form monophyletic clade in the three trees; however, the inter-subfamily relation was inconsistent (Figure 1). These inconsistencies may be solved when more ant mitogenomes are available. The mitogenome of O. glaber will contribute in understanding the phylogenetics of both the species complex and family Formicidae.

Figure 1.

(A) Lateral view of an Ochetellus glaber worker (KFDS00124; J. Park; IN). (B) Head view of O. glaber worker (KFDS00124; J. Park; IN). (C) Maximum likelihood (bootstrap repeat is 1,000), neighbor joining (bootstrap repeat is 10,000), and bayesian inference (1,100,000 generations) phylogenetic trees of all available Dolichoderine ant mitochondrial genomes: Ochetellus glaber (MN044390 in this study), Linepithema humile (NC_045057 and KT428891), Dorymyrmex brunneus (MG253267), Leptomyrmex pallens (NC_023093), Dolichoderus sibiricus (NC_041075), as well as 13 ants form other subfamilies: Pseudomyrmex gracilis (BK010472), Tetraponera rufonigra (BK010387), Ooceraea biori (CM010870), Ectatomma ruidum (MG870227), Ectatomma tuberculatum (MG870211), Myrmica scabrinodis (NC_026133), Solenopsis invicta (NC_014672), Pristomyrmex punctatus (NC_015075), Camponotus atrox (NC_029357), Anoplolepis gracilipes (NC_039576), Formica fusca (NC_026132), Cryptopone sauteri (NC_041202), Ectomomyrmex javanus (NC_042678), and a honey bee, Apis mellifera ligustica (NC_001566) as an outgroup species. Phylogenetic tree was drawn based on maximum likelihood tree. The numbers above branches indicate bootstrap support values of maximum likelihood and neighbor joining trees, and posterior probability of bayesian inference tree, respectively.