The iconic baobab tree, known for its distinctive “upside-down” appearance, has always held a shroud of mystery around its evolutionary origins. A recent study has delved into the genetic makeup and historical distribution of all eight baobab species to unravel their tangled evolutionary history.
The research revealed that the progenitor of the eight living baobab species emerged on the island of Madagascar approximately 41.1 million years ago. The first recognizable baobab materialized 21 million years ago, setting the stage for the diversification of daughter species between 20.6 million and 12.6 million years ago. Hybridization, a phenomenon known as reticulate evolution, contributed to the genetic diversity of baobabs. Additionally, mountain uplift and volcanism played a role in creating diverse habitats, fostering the separation of baobab species into distinct lineages.
Intriguingly, the study also highlighted the ambiguity surrounding the dispersal of baobabs beyond Madagascar. Some theories suggest that ocean currents carried baobab fruits to distant shores, while others speculate that birds may have played a role in the case of Australia. Despite these hypotheses, the exact mechanism of their long-distance dispersal remains an unsolved puzzle.
Unfortunately, the majestic baobab faces threats from both drought and human activities. Three of the eight species are now classified as threatened, and two of those, Adansonia perrieri and Adansonia suarezensis, exhibit high levels of inbreeding, further complicating their survival prospects. Volcanic activity and sea-level rise have also diminished their preferred habitats within the past million years.
Furthermore, conflicts between baobab species add another layer of complexity to their conservation. Adansonia digitata and Adansonia grandidieri are more adaptable and compete with endangered species, which have more specific habitat requirements. This interspecies competition poses additional challenges to the long-term survival of these remarkable trees.
