Phylogenetic relationships and divergence time estimates in the genus Echinops L. (Asteraceae)

Abstract

This study focuses on the phylogenetic relationships among taxa within the genus Echinops, in particular the taxa distributed in Turkey, since their systematic characterization and sectional taxonomy have not previously been fully determined. We used sequences of the plastid trnL‐trnF, rbcL, matK and nrDNA ITS gene regions obtained from this study and GenBank to reconstruct phylogenetic relationships among Echinops taxa based on Bayesian inference. In addition, divergence times of taxa within the genus were estimated by the Bayesian method using a relaxed clock model. In the phylogenetic tree, E. acantholepis, an annual species, was first split from all other echinops taxa and this split was estimated to have occurred approximately 19.99 Mya. Next, E. emiliae, a biannual species, separates from the other species, and finally forms a group with the perennial Echinops taxa. We were also to predict differences in the rate of speciation by comparing different gene regions. The results indicate that the number of sections of the genus Echinops distributed in Turkey should be increased from three to five by the addition of the sections Psectra and Acantholepis. Furthermore, it is indicated that some taxa currently treated as subspecies may deserve recognition at the species level. Our results also support previous studies suggesting that it is appropriate to incorporate the monotypic Acantholepis in Echinops and transfer A. orientalis to the genus Echinops under the name E. acantholepis. Consequently, it is concluded that the studied gene regions were significant and informative for resolving phylogenetic relationships among the taxa of Echinops.