Re-evaluation of the phylogenetic relationships and species delimitation of two closely related families (Lamiaceae and Verbenaceae) using two DNA barcode markers.

The families Lamiaceae and Verbenaceae comprise several closely related species that possess high morphological synapomorphic traits. Hence, there is a tendency of species misidentification using only the morphological characters. Herein, we evaluated the discriminatory power of the universal DNA barcodes (matK and rbcL) for 53 species spanning the two families. Using these markers, we inferred phylogenetic relationships and conducted species delimitation analysis using four delimitation methods: Automated Barcode Gap Discovery (ABGD), TaxonDNA, Bayesian Poisson Tree Processes (bPTP) and General Mixed Yule Coalescent (GMYC). The phylogenetic reconstruction based on the matK gene resolved the relationships between the families and further suggested the expansion of the Lamiaceae to include some core Verbanaceae genus, e.g., Gmelina . The rbcL marker using the TaxonDNA method displayed high species delimitation resolutions, while the ABGD, GMYC, and bPTP generated different number of Operational Taxonomic Units/genetic clusters. Our results underscored the efficiency of the matK and rbcL genes as reliable markers for resolving phylogenetic relationships and species delimitation of both families, respectively. The current study provides insights into the DNA barcode applications in these families, at the same time contributing to the current understanding of genetic divergence patterns in angiosperms.