The baobab (Adansonia), a genus of trees with eight existing species, has long captivated human admiration. Despite this fascination, the origins of baobabs have remained mysterious.

Recent genomic and ecological analyses by a global research team led by the Sino-Africa Joint Research Center, CAS, hosted by the Wuhan Botanical Garden of the Chinese Academy of Sciences, have shed light on the origins and dispersal of these iconic trees.

The study reveals that Madagascar is the cradle from which all other baobab species emerged. This discovery has significant implications for understanding and conserving these remarkable trees in rapidly changing environments. By delving into the genetics of baobabs, researchers hope to uncover clues to aid in their conservation.

Madagascar, renowned for its unique and intriguing flora and fauna, is home to the magnificent baobab tree, often referred to as the “mother of the forest” and the “tree of life”. Despite their cultural significance and impact, much about the baobabs’ evolutionary history remained unknown until now.

Summary of the predicted evolutionary history of baobabs under the Malagasy origin hypothesis, showing the likely migratory routes of A. digitata and A. gregorii. The location of an ancient and controversial land bridge49,50 between Africa and Madagascar is shown (dotted box) along with key evolutionary events
Summary of the predicted evolutionary history of baobabs under the Malagasy origin hypothesis, showing the likely migratory routes of A. digitata and A. gregorii. The location of an ancient and controversial land bridge49,50 between Africa and Madagascar is shown (dotted box) along with key evolutionary events. Credit: Jun-Nan Wan et al. / Nature

Using high-quality genomic data from the eight existing species of baobabs, the research team has proposed an evolutionary history for the baobab lineage. The data point to an origin in Madagascar, followed by dispersal to Africa and Australia. Factors such as climate, pollinating animals, and local sea level changes have shaped each species to its environment.

Dr. Wan Junnan, the study’s lead author and a researcher at the Wuhan Botanical Garden, explained, What we see today in Madagascar’s baobabs is heavily influenced by interspecies competition and the island’s geological history, particularly changes in local sea levels. This understanding is crucial for predicting how climate change and habitat loss might affect other baobab species.

The researchers extrapolated that baobabs were more likely to disperse and expand when sea levels were lower, based on global sea level averages over the past 10 million years. This suggests that rising sea levels due to climate change could hinder baobab population expansion, potentially having already impacted them.

Baobabs
Baobabs. Credit: dtemps / depositophotos.com

The combination of limited expansion potential and the specific ecological niches baobabs occupy spells trouble for their populations. Habitat loss for both the trees and their pollinators, like fruit bats and hawks, exacerbates the conservation challenge.

In light of these findings, researchers have called for a reassessment of baobab species’ statuses on the IUCN Red List of Threatened Species. They suggest that some species be reclassified from endangered to critically endangered, which requires acknowledging the causes of decline and a population decrease of at least 90%, as observed in certain baobab species.

The ongoing genetic and historical research aims to preserve baobabs in the ever-changing global landscapes. To further conservation efforts and highlight the trees’ distinctive characteristics, the researchers plan more baobab sampling to clarify the evolutionary history of Madagascar’s baobabs. Beyond this study, further advancements in understanding Madagascar’s floral diversity should follow.


Sources

Chinese Academy of Sciences | Wan, JN., Wang, SW., Leitch, A.R. et al. The rise of baobab trees in Madagascar. Nature (2024). doi.org/10.1038/s41586–024–07447–4


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