The role of the Southern Hemisphere in the evolutionary history of Apiaceae, a mostly north temperate plant family

Abstract

Aim: To estimate the most likely pathways of expansion of the first diverging lineages of the angiosperm family Apiaceae across the Southern Hemisphere and to Eurasia by reconstructing the biogeographical history of the family through space and time. Location: Southern Hemisphere, with emphasis on Africa. Methods: Divergence times were assessed under a penalized-likelihood method (r8s) and a data set of 129 cpDNA rps16 intron sequences. Confidence intervals were estimated using ABCq, BCa, bootstrap-t and standard normal methods. Biogeographical distributions were reconstructed using DEC analyses over rps16 intron and/or nrDNA ITS trees. Results: Crown Apiaceae likely originated by the Late Cretaceous in Australasia. Apiaceae subfamilies diverged between 45.9 and 71.2 Ma in the Southern Hemisphere, specifically, Mackinlayoideae in Australasia, Azorelloideae in South America and Apioideae and Saniculoideae in southern Africa. From the Palaeocene to Oligocene, Africa showed connections via transoceanic dispersals as a sink continent with Australasia and as a source continent with South America and Eurasia. These dispersals explain the present intercontinental disjunctions of the subfamilies. The first diverging lineages of Apioideae and Saniculoideae likely originated in Africa and diversified in situ since the Palaeocene, with no input from newcomers until the Miocene. Subsequently, several dispersals mainly from Eurasia are estimated back to northern and eastern Africa. Main conclusions: The Southern Hemisphere has played a key role in the origin and early diversification of Apiaceae, currently a mostly north temperate family. African Apiaceae was likely assembled by Palaeocene lineages that diversified in situ and are now restricted mainly to southern Africa and post Miocene newcomers mostly restricted to northern and eastern Africa by effective environmental barriers.