Introduction
Tenebrionoidea is a large superfamily in Coleoptera, with over 34,000 known species and 28 families (Lawrence, 1995; Ślipiński et al ., 2011). The species in the superfamily have the 5-5-4 tarsal formula in both sexes, with occasional 4-4-4, 3-3-3 or 3-4-4 in males. Members of the superfamily demonstrate various types of feeding strategies, the majority of which are fungivorous, xylophagous, and saprophagous. Some Tenebrionoidea species are major agricultural and forest pests, which attack commercial crops or stored products (Song et al ., 2018). They are widely spread throughout all terrestrial habitats from the sea shore up to dry desert and steppe habitats in all altitudinal belts, and in all types of forests, and species in arid environments are conspicuously diverse. Given these diverse feeding strategies and habitats, the morphology of the superfamily is complicated (Bouchardet al. , 2009). Taxonomic and phylogenetic studies are essential for understanding their biodiversity and biological characteristics, and for further protecting, utilizing and controlling them.
The framework of the classification system for Coleoptera was firstly established in 1955 and then revised in 1982, in which the Tenebrionoidea is divided into 5 lineages: 1) Tetratomidae, Melandryidae, Mordellidae, Ripiphoridae; 2) Synchroidae, Zopheridae, Prostomidae, Perimylopidae, Chalcodryidae, Tenebrionidae; 3) Oedemeridae, Stenotrachelidae, Meloidae; 4) Pythidae, Pyrochroidae, Boridae, Mycteridae, Salpingidae; and 5) Anthicidae, Aderidae, Scraptiidae (Crowson, 1955; Lawrence & Newton, 1982). In past years, a number of studies have been reported to establish the taxonomy system of Tenebrionoidea using comparative morphology data (Beutel & Friedrich, 2005; Lawrence et al ., 2011). Nowadays, 28 families (Mordellidae, Ripiphoridae, Anthicidae, Meloidae, Pyrochroidae, Oedemeridae, Salpingidae, Scraptiidae, Lagriidae, Tenebrionidae and so on) are widely recognized for Tenebrionoidea (Bouchard et al ., 2011). Despite of economic importance, the monophyletic status of many families and phylogenetic relationships in Tenebrionoidea need to be elucidated. A comprehensive phylogeny study of beetles showed the three families Mordellidae, Anthicidae and Meloidae are monophyletic, the Scraptiidae is paraphyletic based on 18SrRNA, 16S rRNA and COX1 gene sequences (Hunt et al ., 2007). The phylogenetic analysis of Coleoptera showed that the families Tenebrionidae, Oedemeridae, Salpingidae, Mordellidae, Meloidae and Scraptiidae are monophyletic; Pyrochroidae is polyphyletic based on four gene (16S rRNA, COX1, 28S and 18S ) sequences (Bocak et al ., 2014). The higher-level phylogenetic analysis of beetles indicated that the Tenebrionidae, Oedemeridae, Salpingidae, Pyrochroidae, Meloidae and Scraptiidae are monophyletic, whereas Anthicidae is paraphyletic based on 95 nuclear protein-coding genes from 373 beetle species (Zhanget al. , 2018). Almost all molecular phylogenetic analyses support the monophyly of Mordellidae and Meloidae, which is inconsistent with the phylogenetic analyses based on morphological data (Lawrenceet al ., 2011). Due to incongruent phylogenetic relationships from different analysis, the phylogenetic relationships and monophyly among families are still not well settled, and the phylogenetic positions among some families are contradictory in different molecular studies. All of these phylogenetic issues urgently need to be elucidated.
With the characteristics of conservative gene content, simple genome organization, maternal inheritance, small genome size and higher evolution rate, complete mitochondrial genome (mtgenome) has been widely used in molecular phylogenetics, evolution, and population genetics study of insects (Cameron et al ., 2014). Up to date (October 2021), there have been 71 species of Tenebrionoidea complete mtgenomes to be reported in GenBank, covering 15 families in Tenebrionoidea. However, there is no complete mtgenome sequence to be reported from the families Archeocrypticidae, Stenotrachelidae and Melandryidae, and the characteristics of the mtgenomes is still little understood in the superfamily. Up to now, there have been only a few mtgenome-based phylogenetic studies at high taxa in Tenebrionoidea. A mtgenome-based phylogenetic inference of beetles indicated that the families Tenebrionidae, Oedemeridae, Anthicidae, Mordellidae and Meloidae were monophyletic, whereas Scarptiidae was polyphyletic based on 245 mitochondrial sequences using Bayesian method (Timmermans et al. , 2015). The phylogenetic analysis of 37 beetle mitochondrial genes supported the Mordellidae and Meloidae to be monophyletic groups, and the Scraptiidae and Melandryidae to be paraphyletic groups using Bayesian inference (Song et al. , 2018). The mtgenome-based phylogeny of 51 beetles found that the monophyletic of Meloidae, Tenebrionidae, and the sister relationship of Meloidae and Tenebrionidae using Bayesian inference (Tang et al. , 2020). As mentioned above, previous mtgenome-based phylogenetic studies have not well resolved the phylogeny of Tenebrionoidea, and phylogenetic analysis of the superfamily need to be further evaluated.
In this study, we newly sequenced and annotated 19 species of complete mtgenomes, and comparatively analyzed the mtgenome characteristics of a total of 90 species in Tenebrionoidea. More importantly, we constructed and discussed the phylogenetic relationships at high taxa level based on these mtgenome sequences, and inferred the divergence time at main nodes in the phylogenetics in inference of fossil records. This study lays a foundation for further understanding of mtgenome characteristics, phylogenetics and evolution of the Tenebrionoidea.