The C enozoic biogeographical evolution of woody angiosperms inferred from fossil distributions

Aim We test whether the modern regionalization of the angiosperm flora is the result of C enozoic barriers to dispersal. Location Global. Methods We used a database of C enozoic woody angiosperm fossils to build a matrix of family and genus occurrence at 11 continents/regions for five time periods of the C enozoic, thus defining 55 floras. We used ordinations and cluster analyses to infer the relationships among these floras. We tested for the effects of time, land connections and dispersal barriers on the similarities between these woody angiosperm floras. Results For all time periods of the C enozoic the world's woody angiosperm floras were grouped into three large clusters: a very compact N orthern H emisphere cluster ( N orth A merica, E urope, temperate A sia and P alaeogene south C hina), a somewhat less compact P alaeotropical cluster ( A frica, I ndia, S outheast A sia and N eogene south C hina) and a rather diffuse G ondwanan cluster ( A ntarctica, A ustralia, N ew Z ealand, temperate S outh A merica and the N eotropics). The primary clustering is evidently geographical, and reflects the barriers formed by the T ethys and the southern Atlantic–southern I ndian oceans. There is evidence that the more recent Gondwanan floras are more divergent than the older floras, possibly due to long isolation by oceans and multiple extinction events, whereas the similarities among N orthern H emisphere floras increased during the N eogene. Main conclusions The modern regionalization is mainly the result of dispersal barriers that existed at diverse times in the C enozoic, resulting in several woody angiosperm floras that evolved in parallel. Climatic change and dispersal also played important roles in shaping biogeographical patterns of C enozoic woody angiosperms.