Amphitropic amphiantarctic disjunctions in Apiaceae subfamily Apioideae

Aim Four genera of the plant family Apiaceae subfamily Apioideae –Apium,Chaerophyllum,DaucusandLilaeopsis– are characterized by amphitropic and amphiantarctic distribution patterns, and in Australasia the subfamily is also represented by the tribe Aciphylleae. We infer the molecular ages of achieving amphitropic distribution for these lineages, reconstruct the biogeographical histories ofApium,Chaerophyllum,DaucusandLilaeopsis, and identify the sister group of Aciphylleae. Location Worldwide, with an emphasis on South America and Australasia. Methods Divergence times were estimated employing a Bayesian approach (beast) with fossil pollen of basal apioids as calibration points and using a data set of nuclear ribosomal DNA internal transcribed spacer (nrDNA ITS) sequences from 284 accessions of Apioideae. Additionally, maximum‐likelihood analyses were performed for data subsets comprisingApium,DaucusandLilaeopsis. ForChaerophyllum, maximum‐likelihood andbeastanalyses were carried out using combined chloroplast DNA and ITS data. Biogeographical scenarios were inferred usingdivaandlagrange. Results The sister group to Aciphylleae is the Sino‐HimalayanAcronemaclade and the divergence between these two lineages is dated at 34.8 Ma, whereas the radiation of Aciphylleae started 11.0 Ma. A Northern Hemispheric origin was inferred forApium,ChaerophyllumandDaucus, whereasLilaeopsisprobably originated in South America following a dispersal of its ancestor from North America.Chaerophyllum,DaucusandLilaeopsisdispersed to the Southern Hemisphere at 5.3, 7.0 and 27.9 Ma, respectively. ForApium, two dispersals from Europe were inferred: to South America at 6.3 Ma, and to southern Africa at 3.9 Ma. The taxa migrated along the land masses of North and South America (Daucus,Lilaeopsis) and Africa (Apium) or by direct transoceanic dispersals through the Atlantic (Apium) or the Pacific (Chaerophyllum). Within the Southern Hemisphere they dispersed both westwards (Apium,Daucus,Lilaeopsis) and eastwards (Chaerophyllum,Lilaeopsis). ForChaerophyllumandLilaeopsis, subsequent dispersal events to the Northern Hemisphere were also inferred. Main conclusions Similar timing, contrasted with the diversity of migration routes, suggests that the dispersal events of these umbellifer taxa (and many other amphitropic amphiantarctic genera) were facilitated by favourable ecological conditions in the Southern Hemisphere (climatic cooling of the late Palaeogene/early Neogene) rather than by increased dispersal opportunities.