Banksias: Iconic Australian Vegetation with North African Roots

Few crops conjure up the Australian bush higher than banksias, whose lovely flowers are irresistible to honeyeater birds, small marsupials and nature lovers.

However our analysis, revealed in Views in Plant Ecology, Evolution and Systematics, reveals that the ancestors of banksias truly migrated right here from North Africa.

From early fossil pollen research, we already knew that the protea household (Proteaceae), which incorporates banksias, grevilleas, waratahs and macadamias in Australia, originated in northwest Africa 130 million years in the past.

Our job was to trace their migration to Australia, the place they turned the distinctive symbols of the Australian bush that we admire immediately. To provide credit score the place it is due, we have to know the place our pure heritage originated. So, how did this iconic group of crops get right here?

Wanting on the whole household

Our examine relied on two approaches. We used a DNA evaluation of the complete protea household to create an evolutionary tree. Then we inserted key fossil pollen data of a identified age into the tree, to function a “molecular clock”. This helped us work out the time of origin of all genera on this household.

We then searched the literature for data of historic sedimentary deposits that include fossil pollen with affinities to banksias in Africa, South America, Antarctica (which was coated in forest till 40 million years in the past) and Australia.

This was made attainable by the very fact the laborious partitions of pollen grains permit them to be preserved for thousands and thousands of years. Additionally, the pollen grains of crops within the protea household are fairly distinctive from these of different households. We then in contrast the dates and places of the fossil pollen in opposition to our household tree.

This confirmed that by 120 million years in the past, the ancestors of banksias had begun crossing into northeast South America. The 2 continents remained joined at their ideas till 100 million years in the past.

The crops then migrated down the east aspect of South America – first reaching the Scotia Isthmus about 110 million years in the past – and crossed onto the Antarctic Peninsula.

Two routes into Australia

Right here, the ancestors separated into two teams. One, the soft-leaved group, adopted a cool-temperate rainforest pathway (darkish for as much as 4 months of the yr) alongside the south aspect of Antarctica. They entered Australia through Tasmania from 105 million years in the past.

The rainforest components continued up the east coast, with some ultimately reaching New Guinea; others entered New Caledonian rainforests straight from southern Antarctica. This route remained open till 45 million years in the past, when Australia and Antarctica lastly separated.

The opposite, hard-leaved group adopted an open, fire-prone woodland pathway alongside the hotter, sunnier northern aspect of Antarctica. They entered Australia through the southwest tip that remained hooked up to Antarctica till about 70 million years in the past.

The 2 factors of entry have been separated by an enormous inland sea that occupied the Nice Australian Bight throughout that interval.

A proliferation of banksias

Since banksia itself seems to have arisen 100 million years in the past, the genus both advanced in northeast Antarctica or on the excessive nook of southwestern Australia. From there, they unfold to the remainder of Australia over the following 50 million years.

Banksias now encompass round 200 species, 90% of that are endemic to southwestern Australia. Ancestors of the majority of the hard-leaved genera, reminiscent of grevilleas, hakeas, macadamias and waratahs, additionally entered Australia through the southwestern tip. They then migrated east alongside the margins of the Nullarbor Plain – thickly vegetated again then – to southeast Australia.

Till the outcomes of our new examine, it was believed the protea household arose in Australia and unfold from right here to Africa, South America, New Caledonia and Asia. Nearly all migration would have wanted to be over the oceans, because it was thought to have occurred after the breakup of the Gondwanan supercontinent.

In truth, the journey was fully overland because it occurred when Gondwana was largely intact, apart from the early departure of Larger India.

Vegetation out of Africa

Anthropologists are eager to level to the “out of Africa” speculation for the origin and migratory historical past of people. It now seems such a speculation is equally relevant to some essential teams of crops.

That is the primary time the southwest nook of Australia has been recognised as a significant migratory route for the protea household.

We now have to take critically the Antarctic-southwest Australian hyperlink as a probable main entry route for a lot of different hard-leaved plant teams into Australia. They may have originated in Antarctica and South America, and probably even Africa.

This north Antarctic pathway would possibly properly additionally apply to eucalypts, whose oldest data are for southern South America, in addition to at the moment endemic animals and microbes.

Byron Lamont receives funding from the Australian Analysis Council

Lynne Milne is a member of the Australian and New Zealand Forensic Society and the American Affiliation of Stratigraphic Palynologists. She is at the moment the Treasurer of the Royal Societies of Australia.

Tianhua He acquired funding from the Australian Analysis Council.

Richard Cowling doesn’t work for, seek the advice of, personal shares in or obtain funding from any firm or organisation that may profit from this text, and has disclosed no related affiliations past their educational appointment.

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