The fossil record of Berberis (Berberidaceae) from the Palaeocene of NE China and interpretations of the evolution and phytogeography of the genus

Extant Berberis is a member of the basal eudicots with a South America (group Australes)-Old World (group Septentrionales) disjunctive distribution pattern. Different hypotheses have been proposed to explain the formation of this pattern. Recent molecular studies suggest that this pattern was caused by a vicariance event in the Cretaceous. More fossil evidence is required to evaluate these hypotheses. Here a new species of Berberis from the Palaeocene Wuyun flora is established based on a detailed comparison with all other fossil and related living Berberis. The occurrence of a Palaeocene Berberis in NE China and other fossil data suggest that 1) the genus originated in eastern Asia, 2) the leaf venation of the genus probably evolved from pinnate to acrodromous, leaf margins from densely spinose teeth to only occasionally toothed or even entire, 3) the genus would appear to have migrated from eastern Asia to North America in the Oligocene, via Beringia. Berberis probably arrived in Europe from Asia during the late Oligocene when Eurasia was reunited after the retreat of the Turgai Straits. Berberis could have migrated to India from eastern Asia, arriving before the last major upheaval of the Himalayas in the Pleistocene.