How did the break-up of Gondwana affect the distribution of the flora and fauna present in Australia?
The break-up of Gondwana into several smaller continents had the initial effect of dividing the once uniform biota between the different new continents and isolating segments of once uniform gene pools. These isolated segments were then able to drift genetically and slowly evolve new species and entire new biotas. A later change in climate caused dramatic changes in the nature of the biota and forced evolution and adaptation at a faster pace, giving each fragment of Gondwana a unique and different biota. Another even later effect was to raft the isolated biotas to different localities and into contact with new and different biotas. This allowed migration both to and from Australia, and introduced new biotic elements from the older Gondwanan and Laurasian landmasses of south-eastern Asia. What evidence is there for the evolution of eucalypts in Australia? Evidence that the eucalypts evolved in Australia is mainly circumstantial. The majority of species now occur in Australia, with only
