TheCenozoic biogeographical evolution of woody angiosperms inferred from fossil distributions

Abstract

AbstractAimWe test whether the modern regionalization of the angiosperm flora is the result ofCenozoic barriers to dispersal.LocationGlobal.MethodsWe used a database ofCenozoic woody angiosperm fossils to build a matrix of family and genus occurrence at 11 continents/regions for five time periods of theCenozoic, 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.ResultsFor all time periods of theCenozoic the world's woody angiosperm floras were grouped into three large clusters: a very compactNorthernHemisphere cluster (NorthAmerica,Europe, temperateAsia andPalaeogene southChina), a somewhat less compactPalaeotropical cluster (Africa,India,SoutheastAsia andNeogene southChina) and a rather diffuseGondwanan cluster (Antarctica,Australia,NewZealand, temperateSouthAmerica and theNeotropics). The primary clustering is evidently geographical, and reflects the barriers formed by theTethys and the southern Atlantic–southernIndian 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 amongNorthernHemisphere floras increased during theNeogene.Main conclusionsThe modern regionalization is mainly the result of dispersal barriers that existed at diverse times in theCenozoic, resulting in several woody angiosperm floras that evolved in parallel. Climatic change and dispersal also played important roles in shaping biogeographical patterns ofCenozoic woody angiosperms.