ITS phylogeny of West Asian Heracleum species and related taxa of Umbelliferae–Tordylieae W.D.J.Koch, with notes on evolution of their psbA-trnH sequences

Abstract

Heracleum is a large and taxonomically complex genus of the Umbelliferae–Tordylieae. The phylogenetic relationships of West Asian Heracleum species and related taxa were explored using data from sequences of the internal transcribed spacer (ITS1 and ITS2) region of nuclear ribosomal DNA. The data set consists of 56 species, of which 47 were analyzed for the first time; it represents all subdivisions of the genus Heracleum, as well as some representatives of Pastinaca complex. Heracleum was shown to be a polyphyletic genus, as its species fall into two different clades, one of which comprises also Symphyoloma and Mandenovia. Section Pubescentia was confirmed, in contrast to the sections Villosa and Heracleum being polyphyletic. A separate position of the section Wendia was supported. H. marashicum was shown to be a member of a clade comprising Pastinaca and related genera. The sequences of chloroplast psbA-trnH intergenic spacer, the region recently proposed for DNA barcoding in plants, were also analyzed for 33 species, representing all principal clades within Heracleum and its relatives. They have been proven to be very similar and not suitable for DNA barcoding in this group. However, some sequence variation was revealed. This variation could be explained by the combination of such evolutionary events as inversion and duplication. It was shown that these events are rather common in Tordylieae and can occur independently in different lineages. The evolution patterns of psbA-trnH spacer are hypothesized.