Divergence times and morphological evolution of the subtribe Eritrichiinae (Boraginaceae-Rochelieae) with special reference to Lappula

Abstract

The subtribe Eritrichiinae belongs to tribe Rochelieae (Borginaceae; Cynoglossoideae) which is composed of about 200 species in five genera including Eritrichium, Lappula, Hackelia, Lepechiniella, and Rochelia. The majority of the species are annual and grow in xeric habitats. The genus Lappula as an arid adapted and the second biggest genus of Eritrichiinae with over 50 species is distributed predominantly in Irano-Turanian region. Here, we employed BEAST Bayesian inference for divergence time estimation based on nrDNA ITS, plastid trnL-F and rpl32-trnL (UAG) sequence data of 46 species of Eritrichiinae extracted from GenBank. The results obtained from molecular dating analyses indicated that the date of Eritrichiinae crown group back to late Oligocene. Diversification events took place for Lappula in Asia from the late Miocene to the late Pleistocene. The North American species have been derived from the Asian relatives at the late Miocene.