Baobabs are one of the world's most remarkable trees.
Their appearance alone is astonishing enough – huge, bulging trunks with root-like crowns, it's easy to see why they are also known as 'upside-down trees'.
Now new research, published in the journal Nature, sheds light on the origins of these charismatic trees, their epic dispersal around the world, and how they exploited (and continue to exploit) hawkmoths, bats and lemurs to survive.
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Meet the upside-down tree
Baobabs are part of a genus of tree with distinctive swollen trunks that store water to endure harsh droughts. They can reach enormous sizes and have long lifespans, with some specimens living thousands of years.
The trees play a vital ecological role, providing shelter, food and water for various animals, including humans. Their nutritious fruit, leaves and bark hold cultural significance, used in traditional medicine and culinary practices, making them a symbol of resilience and sustenance in arid landscapes, hence its second epithet, 'tree of life'.
There are eight species of baobab tree, spread across Africa, Madagascar and Australia. But where did they originate and how did they travel around the world?
A team of international researchers think they finally have the answer.
The wandering baobab
In a new collaborative study, involving Wuhan Botanical Garden (China), Royal Botanic Gardens, Kew (UK), University of Antananarivo (Madagascar) and Queen Mary University of London (UK), scientists reported a remarkable example of species radiation in Madagascar, followed by long-distance dispersal to Africa and Australia.
The team compiled the genomes of the eight acknowledged species of baobab and worked out their speciation patterns, before analysing the genomes.
They discovered that the ancestor of all eight species likely proliferated in Madagascar, where hybridisation occurred.
Remarkably, two species then embarked on extensive migrations across the world – one to Africa and the other to Australia.
During this radiation, the species underwent evolutionary changes in their flower structures, according to the study, adapting to their new surroundings to attract hawkmoths, lemurs and bats.
“We were delighted to be involved in this project uncovering patterns of baobab speciation in Madagascar followed by the astonishing long-distance dispersal of two species, one to Africa and another to Australia," says Professor Andrew Leitch at Queen Mary University of London.
"This was accompanied by the evolution of some fascinating pollination syndromes involving hawkmoths, lemurs and bats.”
Dr Ilia Leitch at Royal Botanic Garden Kew adds, “this work has uncovered new insights into the patterns of speciation in baobabs and shows how climate change has influenced baobab distribution and speciation patterns over millions of years.”
The findings were published in the paper 'The rise of baobab trees in Madagascar'.
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