Complete mitochondrial genomes throw light on budding speciation in three Biston species (Lepidoptera, Geometridae)

Biston panterinaria, Biston thibetaria and Biston perclara are very closely related species in the genus Biston, judged on the basis of both morphological and molecular evidence. The distribution area and altitudes, and host plants of these three species also show both consistency and differences. However, the exact relationship between the three species is unclear. In this study, we used the 'distance-based method', the 'tree-based method' and Bayesian phylogenetics and phylogeography to elucidate the relationship between the three species. Phylogenetic trees based on mitogenomes, COI+CYTB+16S and three nuDNA genes were constructed. The results of the phylogenetic trees revealed that B. thibetaria and B. perclara were derived from B. panterinaria and render the latter paraphyletic. The budding process of speciation is therefore presumed to be the main factor causing a phylogenetic relationship of this pattern. A host shift from broad-leaved plants living at low altitudes to gymnosperms living at relatively high altitudes provides evidence of budding speciation in these three species. The divergence time suggests that the budding speciation occurred at approximately 1.38 Ma, which is consistent with the Kunlun-Yellow River Movement. Tectonic movements occurring around the Qinghai-Tibet Plateau may be the driver of the budding speciation.