The Botanical Status of the COM Clade in Rosidae

Abstract The taxonomic status determination of populations plays a crucial role in the conservation and management of global biodiversity. The Celastrales–Oxalidales–Malpighiales (COM) clade, an important component of Rosidae, holds a significant position within the angiosperms. In this study, systematic phylogenetic analyses were conducted on the mitochondrial genomes, chloroplast genomes, and nuclear genomes of all sequenced species within the COM clade using three different methods. Phylogenetic analysis of eight conserved mitochondrial genes from 34 plant species revealed that under high-confidence conditions, the COM clade is not affiliated with fabids or malvids, indicating a parallel relationship. However, analysis of four additional conserved mitochondrial genes suggested a closer affinity of the COM clade to malvids than to fabids. A phylogenetic analysis of 49 conserved chloroplast genes from 57 plant species showed that the COM clade is parallel to both fabids and malvids, rather than belonging to either group. The results from 45 chloroplast genes indicated that the three subgroups within the COM clade are parallel to each other and parallel to fabids and malvids. The majority of results from the four conserved genes support a parallel relationship between the main branch of COM and malvids, with a closer affinity to fabids than to other groups. A systematic phylogenetic analysis of 879 conserved nuclear genes from five fabid species, five malvid species, and all species within Celastrales, Malpighiales, and Asteridae revealed that the three subgroups within the COM clade are parallel to each other and parallel to fabids and malvids under high-confidence conditions. In conclusion, the systematic phylogenetic trees based on mitochondrial genomes, chloroplast genomes, and nuclear genomes of all analysable conserved genes collectively demonstrate that the COM clade belongs to neither the fabids nor the malvids but is parallel to them.