History of Australian Plants
The Australian flora includes many species of plant that is estimated to have more than 20,000 vascular and around 14,000 such plants that are non-vascular. It has strong similarities with the Gondwana flora, whose range was formed due to continental drift and significant changes in the climate since the Cretaceous.
Notable features of the Australian flora are adaptations to dryness which include serotiny and scleromorphy. From the large and popular families like Proteaceae (Banksia), Fabaceae (Acacia - wattle) and Myrtaceae (Eucalyptus - gum trees), such adaptations are common in various species.
Gondwana started to disintegration 140 million years ago. Experts believe that around 20 million years ago, rapid radiation of different species like Casuarina, Eucalyptus, Allocasuarina, the pea-flowered legumes, Banksia, development of open forest and grasslands started to develop from the Eocene. Further, when the Eurasian Plate collided, it led to additional cosmopolitan and south-east Asian elements entering the Australian flora such as the Lepidium and Chenopodioideae.
Also, the arrival of humans approximately 50,000 years ago and the settlement of Europeans in the late 1780s, has had a noteworthy impact on the flora of Australia. The practice of fire-stick farming by Aboriginal Australians people led to significant changes in the distribution of several species of plants. Moreover, the large-scale alteration or demolition of vegetation for agriculture and urban development completely changed the composition of the terrestrial ecosystems that lead to endangered over 1000 plant species and the extinction of 61 more.
Countries like Australia, South America, Africa, India and Antarctica was a small part of the southern supercontinent Gondwana. The modern flora of Australia had their beginning in Gondwana during the Cretaceous period when the subtropical rainforest was all over the nation. The ferns and gymnosperm have substantial similarity to the Gondwanan ancestors. Species like the Myrtaceae, Nothofagus and Proteaceae were also present.
Dutch philologist Pieter Burman the Younger recognised and classified a species of Synaphea and Acacia as the first Australian plants in Linnaean taxonomy in 1768 as Polypodium spinulosum and Adiantum truncatum respectively. He stated that the species were from Java.
Later, both the species were found to be from the Western region of Australia, most likely to have got near the Swan River, during a visit of countryman Willem de Vlamingh in the year 1697.
Indigenous Australians used several species for medicine, food shelter, weapons and tools. For example, Clematis microphylla’s starchy roots were used in western Victoria to prepare food that was baked, the leaves were used as a poultice application to blisters and skin irritations.
Growing aridity has augmented the frequency of fires in the country. Fire is believed to have played a vital role in the progress and spreading of such species that are fire-adapted. A rise in charcoal in deposit around 35,000 years ago matches with dates for the inhabitation of Indigenous Australians.
It further suggests that human-made fires have played an essential role in the formation and maintenance of sclerophyll forest, particularly on the east coast region. Adaptations to heat and light include epicormic and lignotubers buds in Banksia and Eucalyptus species that let the fast renewal after the fire. Some kinds also display serotiny. There are some species such as Xanthorrhoea grass trees that only flower after the fire.
