by For millions of years, great baobabs have stood on three different lands, asking each other an existential question: Who came first?
The huge trees, swollen in the trunk and stubby in the canopy, are unfathomable. Baobabs can live for more than 1,000 years, serving as a key species in dry forest environments in Madagascar, the African continental range, and northwestern Australia. Known as the “mother of the forest” and the “tree of life,” almost every part of the tree can be used by humans and animals, meaning they are of immense value to every ecosystem in which they live.
Only the mystery of where they came from has burned in their reputation. Until now, science has been concerned with multiple conflicting hypotheses – the main theory being that they came from Great Africa. Not so, according to a study published last month in the journal Nature. A team of international academics succeeded in sequencing the genomes of each of the eight baobab species, examining their relationship to each other and concluded that they originated from Madagascar.
The news comes as the trees are deteriorating on the island, where there are six species of baobab, one of which is likely to disappear by 2080 according to the study, unless significant interventions are implemented.
Biologists have struggled to determine the origin of the tree, because no fossils of an ancient baobab or its ancestors have been found, explained Dr. Wan Jun-Nan, one of the authors of the study, a researcher at the Wuhan Botanical Garden in Hubei, China. Previous studies had limited the amount of genetic data obtained from baobabs, he continued. But with the first complete genome sequence of every species, “we can tell a good story about evolutionary history,” he argued.
That story begins with the rise of baobabs in Madagascar around 21 million years ago, before the genus (scientific name Adamson) began to diversify, and two species made their way to Africa and Australia around 12 million years ago. This happened well after the breakup of the “supercontinent” Gondwana, so the baobab probably spread by seeds carried across the ocean on floating debris caused by flash floods, according to the researchers.
The study, a collaboration between the Wuhan Botanical Gardens, China, the Royal Botanic Gardens in the United Kingdom, the University of Antananarivo in Madagascar and Queen Mary University of London, was also able to trace the interspecies gene flow of the eight types of baobab. First time. These data, which showed low genetic diversity between two species, and the inbreeding of one species with another more populous species, provide insight into the competition between baobabs today, Dr Wan said, and could help the trees of tomorrow to protect.
“We hope that in the future the people of Madagascar can take care of baobabs (by) considering them as different species, not as a whole,” he said.
Only one baobab species is included in the IUCN Red List of Threatened Species: A. digital, the population of mainland Africa. Three species in Madagascar are threatened with extinction, and the study recommended the IUCN recategorize one, ie A. suarezensis, from “endangered” to “highly endangered.” Climate modeling has shown that the species could become extinct within 50 years without further intervention.
That prediction is “plausible” and “points to the urgent need for action,” according to Dr. Seheno Andriantsaralaza, a tropical ecologist working in Madagascar.
Dr. supported Andriantsaralaza, who was not involved in the research, with the call to update the IUCN status of certain Malagasy baobabs. While she described the study as “impressive and meaningful”, providing “valuable” insights into genetic data, she cautioned that it was only “one piece of the puzzle to understanding the evolutionary history and dispersal mechanisms of these iconic giant trees .”
The study’s modeling concluded that the range of baobab species on the island has been declining for thousands of years, with human-caused climate change and ongoing deforestation contributing to the shrinking and fragmentation of baobab populations in recent years.
Dr. Andriantsaralaza “it is essential to recognize that, among the challenges, there are local success stories and initiatives led by local organizations and local researchers.”
She mentioned the conservation group Madagasikara Voakajy, which coordinates projects in the north of the island aimed at protecting A. perrieri and A. suarezensis. PEER, a USAID-supported program, also aims to empower local people to contribute to the sustainable management of the ecosystem.
“Madagascar’s baobab forests belong to the local communities who rely on natural resources to feed their families,” she said. “They should be part of the solution, not the problem.”
Dr Wan said he hoped the research and media attention would encourage further conservation efforts for the island’s baobabs.
While praising the progress, he acknowledged the study’s limitations – only one individual per species was sequenced – although he hoped future research would increase sampling and answer more outstanding questions about the trees.
The likelihood of finding fossil evidence to stamp out the conclusions of the genetic data is slim, Dr Wan admitted. So perhaps these majestic trees retain some of their mystery after all.
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