Phylogenetic Reconstruction and Divergence Time Estimation of Blumea DC. (Asteraceae: Inuleae) in China Based on nrDNA ITS and cpDNA trnL-F Sequences

The genus Blumea is one of the most economically important genera of Inuleae (Asteraceae) in China. It is particularly diverse in South China, where 30 species are found, more than half of which are used as herbal medicines or in the chemical industry. However, little is known regarding the phylogenetic relationships and molecular evolution of this genus in China. We used nuclear ribosomal DNA (nrDNA) internal transcribed spacer (ITS) and chloroplast DNA (cpDNA) trnL-F sequences to reconstruct the phylogenetic relationship and estimate the divergence time of Blumea in China. The results indicated that the genus Blumea is monophyletic and it could be divided into two clades that differ with respect to the habitat, morphology, chromosome type, and chemical composition of their members. The divergence time of Blumea was estimated based on the two root times of Asteraceae. The results indicated that the root age of Asteraceae of 76-66 Ma may maintain relatively accurate divergence time estimation for Blumea, and Blumea might had diverged around 49.00-18.43 Ma. This common ancestor had an explosive expansion during the Oligocene and Miocene and two major clades were differentiated during these epochs 29.60 Ma (17.76-45.23 Ma 95% HPD (Highest Posterior Density). Evidence from paleogeography and paleoclimate studies has confirmed that Blumea experienced differentiation and an explosive expansion during the Oligocene and Miocene.