Researchers unravel evolutionary history of baobab trees

WUHAN -- A collaborative effort between Chinese and international researchers has shed light on the evolutionary journey of baobab trees, pinpointing Madagascar as the cradle of all baobab species.

Published on Wednesday in the journal Nature, the study, conducted by researchers from the Sino-Africa Joint Research Center of the Chinese Academy of Sciences and other institutes, represents a significant milestone in terms of better understanding these iconic trees.

Baobabs, a genus with only eight extant species, have their stronghold in Madagascar, where six species exclusively thrive. The other two species are found in lowland areas of the African mainland and the northwestern corner of Australia. Revered due to their cultural and ecological significance, baobab trees are often referred to as "mothers of the forest" and "trees of life" in Madagascar.

Leveraging high-quality genomic data from all eight extant baobab species, researchers embarked on a journey through time to unravel the evolutionary tapestry of baobabs. Their findings suggested that Madagascar probably served as the cradle of baobab diversification, with a subsequent dispersal to the African mainland and Australia.

Their study also underscored the pivotal role played by factors such as paleogeographic events, animal pollinators, and local sea level fluctuations in sculpting the past population dynamic of Malagasy baobabs.

"What we see concerning baobabs in Madagascar today was greatly influenced by both interspecific competition and the geological history of the island, especially changes in local sea levels," said Wan Junnan, the first co-author of the paper and a researcher from the Wuhan Botanical Garden.

The researchers warned that escalating sea levels driven by climate change could impede the natural range expansion of baobabs, potentially exerting adverse effects on their population dynamics.

Armed with a comprehensive understanding of baobab genetics, the researchers hoped to unlock vital clues for the conservation of these trees in the face of rapidly evolving environments.

They underscored the urgent need for conservation efforts, citing the confluence of factors threatening baobab populations, including habitat loss and the decline of key pollinators such as fruit bats and hawkmoths.

Moreover, the researchers advocated for a reassessment of the conservation status of certain baobab species by the International Union for Conservation of Nature (IUCN) Red List of Threatened Species. This recommendation stemmed from findings which revealed their limited genetic variability, small population sizes, and narrow ecological niches (or habitat preferences), making them vulnerable to climate change and other environmental pressures such as land use changes. According to data projection, some baobab species even face a potential precipitous drop in numbers of at least 90 percent.

Such a drastic potential decline warrants reclassification from endangered to critically endangered, highlighting the urgent need for targeted conservation efforts, the study said.

In the future, the researchers intend to expand their sampling efforts regarding baobab trees to advance conservation initiatives and secure greater awareness of their unique attributes.