Mitochondrial genomes of two wild silkmoths, Samia watsoni and Samiawangi (Lepidoptera: Saturniidae), and their phylogenetic implications

Abstract

The wild silkmoth genus Samia Hübner, 1819 (Saturniidae) contains a number of economically important species in industrial silk production. However, the interspecific relationships within the genus remain unclear. We sequence the mitogenomes of Samia watsoni Oberthür, 1914 and Samia wangi Naumann & Peigler, 2001. Both mitogenomes are annotated and found to be cyclized, with 37 genes (13 PCGs, 2 rRNA genes and 22 tRNA genes). Using maximum likelihood and Bayesian inference methods, we analyze these mitogenomes together with a further 68 downloaded from GenBank (65 Bombycoidea and 5 Lasiocampidae as the outgroup) to investigate the phylogenetic relationships both within the genus and those among the three families of the ‘SBS’ group: Bombycidae, Saturniidae and Sphingidae. The results show that within Samia, S. ricini is closely related to S. canningi, and not S. cynthia of which it has previously been considered to be a subspecies. Although arguments have been proposed to treat S. ricini and S. canningi as conspecific, we choose to accept the morphological arguments and continue to treat them as two separate species. Samia watsoni is corroborated as the sister group of all other Samia species, but nevertheless should be included within Samia rather than being placed in its own monobasic genus. Our analysis recovers the following relationship among the three families of the ‘SBS’ group: (Saturniidae + (Bombycidae + Sphingidae)). This agrees with previous studies based on analysis of mitogenomes but continues to contradict the results derived from phylogenomic analysis of nuclear genomes.