The complete mitochondrial genome of Isonychia kiangsinensis (Ephemeroptera: Isonychiidae)

Abstract The complete mitochondrial genome of Isonychia kiangsinensis is a circular molecule of 15,456 bp in length, containing 2 rRNA genes, 13 protein-coding genes, 22 tRNA genes, and a control region. The AT content of the overall base composition is 62.9%. The length of the control region for I. kiangsinensis is 745 bp with 68.6% AT content. In BI and ML phylogenetic trees, Isonychia kiangsinensis was a sister clade to I. ignota and Isonychiidae was shown to be the basal clade of Ephemeroptera excluding Siphluriscidae. The monophyly of the families Isonychiidae, Heptageniidae, Viemamellidae, and Baetidae and the genus Isonychia were well supported.

The family Isonychiidae is composed of one genus (Isonychia) and two subgenera (Isonychia and Prinoides) (Tiunova et al. 2004;Tungpairojwong and Boonsoong 2011). The phylogenetic relationship of Isonychiidae is controversial both in morphological and molecular aspects (Demoulin 1961;McCafferty and Edmunds 1979;Hebert et al. 2003;Ogden and Whiting 2005;Sun et al. 2006;O'Donnell and Jockusch 2008;Ogden et al. 2009;Webb et al. 2012;Saito et al. 2016). More molecular evidence needs to be discovered to clarify the status of this system. Thus, we sequenced the mitochondrial genome of Isonychia kiangsinensis and discussed its phylogenetic relationship within Ephemeroptera.
Samples of I. kiangsinensis were collected in Jingning (27 58 0 22 00 N, 119 38 0 10 00 E), Zhejiang province, China and identified by Dr. Zhang. The total genomic DNA was extracted from the hindleg of I. kiangsinensis using an Ezup Column Animal Genomic DNA Purification Kit (Sangon Biotech Company, Shanghai, China). All mayflies samples and DNA samples were stored in the lab of Dr. Zhang, College of Chemistry and Life Science, Zhejiang Normal University. The universal primers and specific primers for polymerase chain reaction (PCR) amplification were designed as in Zhang et al. (2008).
The mitochondrial genome of I. kiangsinensis showed the typical insect arrangement and is a circular molecule of 15,456 bp length. The AT content of the overall base composition is 62.9%, and the length of the control region is 745 bp with 68.6% AT content. Most of the protein-coding genes (PCGs) used ATN (N represents A, T, C, G) as the initiation codon whereas ND2 and ND5 were initiated by GTG. The COX1, COX2, ND4, ND5, and Cyt b genes used T as the termination codon and the other PCGs ended with TAA or TAG.
Isonychia kiangsinensis was shown to be a sister clade to I. ignota (HM143892). Siphluriscus chinensis (Siphluriscidae) is the basal clade to Ephemeroptera and Isonychiidae is the basal clade to Ephemeroptera excluding Siphluriscidae. The monophyly of the families Isonychiidae, Heptageniidae, Viemamellidae, and Baetidae and the genus Isonychia were well supported in both BI and ML analyses (Figure 1). The monophyly of Siphlonuridae failed to be supported in BI and ML analyses as also reported by Gao et al. (2018). Long branch attraction was found in Baetidae which may affect the phylogenetic relationship between Teloganodidae and Baetidae. In this study, Teloganodidae is a sister clade to Baetidae (Baetis sp. þ Alainites yixiani) as also shown in Gao et al. (2018) but differs from the results of Ogden and Whiting (2005).

Nucleotide sequence accession number
The complete mitochondrial genome of Isonychia kiangsinensis has been assigned the GenBank accession number MH119135.  Figure 1. Phylogenetic tree of the relationships among 22 species of Ephemeroptera, including Isonychia kiangsinensis based on the nucleotide dataset of the 13 mitochondrial protein-coding genes. Numbers above branches specify posterior probabilities as determined from BI (left) and bootstrap percentages from ML (right). The GenBank accession numbers of all species are also shown.