The phylogeny of Ephemeroptera in Pterygota revealed by the mitochondrial genome of Siphluriscus chinensis (Hexapoda: Insecta)

• We sequence mt-genome of the most plesiomorphic mayfly.
• We examine the structure of its mt-genome.
• We construct the phylogenetic tree of 3 basal winged insect clades.
• The Siphluriscus chinensis shows more primitive molecular characteristics.
• The mayfly (Ephemeroptera), not the Odonata, is the sister-group of Neoptera.

The mayfly species Siphluriscus chinensis (Siphluriscidae) has valuable structures useful for phylogeny reconstruction, given its putative basal position within the Ephemeroptera. Here its nearly complete mitochondrial genome is sequenced. We built phylogenetic trees through multiple analytical strategies with some other insect mitogenomes. Structurally, the obtained mitochondrial genome of S. chinensis is 16,616 bp in length,1 containing 37 genes and an extra trnK-like (trnK2 (AAA)) gene. The 12 PCGs start with typical ATN codons, except the nad1 gene which starts with an unnormalized TTG. Like other known mayfly mitogenomes, the strand bias has negative AT-skew and negative GC-skew. Phylogenetically, our topologies suggest that Odonata is the basally diverged clade in Pterygota; Ephemeroptera is the sister group of the Neoptera; and S. chinensis is indeed the most basal mayfly branch.