Across desert and island: Phylogeny of two thin stick insects from China with taxonomic insights into the clade “Gratidiini II” (Phasmatodea, Clitumninae)

Extensive convergence led to poorly understood systematics of stick insects (Phasmatodea) in the past. Both Sceptrophasma bituberculatum and Macellina souchongia belong to the tribe Gratidiini of the family Bacillidae, but they were separated by about 3500 km and inhabit different zoogeographic regions. To further understand the Chinese Phasmatodea, we sequenced the above two species using next-generation sequencing (NGS) and assembled their mitochondrial genomes and standard molecular markers for two phylogenetic analyses. Mitochondrial genome (13 PCGs and 2 rRNAs) phylogeny showed that these two species, originally belonging to the family Bacillidae, were included in the subfamily Clitumninae. Another phylogeny including seven standard molecular markers (four mitochondrial genes: COI, COII, 12S, 16S and three nuclear genes: H3, 18S, 28S), covering more species revealed that: S. bituberculatum is the sister group of Clonaria spp. from Africa; and genus Macellina formed a complex clade with the Oriental Clonaria and Sceptrophasma. Our results corroborate that the family Bacillidae is not monophyletic as currently treated in the Phasmida Species File database and that the genera Clonaria and Sceptrophasma, which span different zoogeographic regions, are not monophyletic and are in need of further revision.