Chloroplast capture and intra- and inter-continental biogeographic diversification in the Asian – New World disjunct plant genus <I>Osmorhiza</I> (Apiaceae)

Abstract

Osmorhiza Raf. (Apiaceae) contains about 12 species disjunctly distributed in temperate Asia, and North, Central to South America. Phylogenetic and biogeographic analyses were carried out applying sequences of two nuclear and nine plastid loci from eleven recognized Osmorhiza species. The nuclear ITS and ETS and the plastid data fully resolved the infrageneric relationships, yet the two phylogenies were largely incongruent. Comparisons of nuclear and plastid phylogenies revealed several interspecific chloroplast transfer events in Osmorhiza, one of which involved an extinct or an unsampled lineage. This genus was inferred to have originated in the Old World during the late Miocene (11.02 mya, 95% HPD: 9.13–12.93 mya), and the crown of the genus was dated to be in the late Miocene (5.51 mya, 95% HPD: 2.81–8.37 mya). Species of Osmorhiza were inferred to have migrated from the Old World into North America across the Bering land bridge during the late Miocene, and they then diversified in the New World through multiple dispersal and divergence events. The intraspecific amphitropical disjunctions between North and South America, and the eastern and western North American disjunctions within O. berteroi and O. depauperata were hypothesized to be via recent long-distance dispersals most likely facilitated by birds.