DNA analysis has revealed a distinct population of Madagascar’s iconic baobab trees, prompting scientists to reinstate the name Adansonia za. The discovery increases the number of baobab species endemic to Madagascar from six to seven.
With its massive swollen trunk and umbrella-shaped branches, the baobab is one of Madagascar’s most recognizable trees. The island is home to six of the world’s eight traditionally recognized baobab species, while another species grows on mainland Africa and one is native to northwestern Australia.
Despite the baobab’s iconic status, scientists have long debated how many distinct species exist in Madagascar and how these remarkable trees are related.
“The baobab tree, genus Adansonia, is one of Madagascar’s most iconic and ecologically important plant groups,” said Dr. Nisa Karimi and her colleagues at the Missouri Botanical Garden.
“Eight species are currently recognized in the genus. One is restricted to northwestern Australia, Adansonia gregorii; another occurs across mainland Africa, Adansonia digitata; and six species are endemic to Madagascar: Adansonia grandidieri, Adansonia madagascariensis, Adansonia perrieri, Adansonia rubrostipa, Adansonia suarezensis, and Adansonia za.”
The researchers noted that the biogeographic and evolutionary history of baobabs had previously been investigated using genomic data. However, earlier studies produced conflicting results and included relatively few samples from Madagascar.
For the new study, the team used targeted DNA sequencing to analyze hundreds of genes, as well as complete chloroplast genomes, from baobab trees collected across Madagascar.
The genetic results showed that populations traditionally classified as Adansonia madagascariensis are not genetically uniform. Northern baobabs were found to be distinct from populations farther south, despite having been assigned to the same species.
The northern population shares more genetic material with two other northern Madagascar species, Adansonia perrieri and Adansonia suarezensis, than with southern populations of Adansonia madagascariensis.
This genetic distinction, combined with differences in leaf shape, fruit stalks, and petal coloration, led the scientists to recognize the northern population as a separate species and revive the name Adansonia za.
The name was first proposed by botanists Joseph Jumelle and Henri Perrier de la Bâthie in 1910, but it had not been used as a valid species designation for more than a century.
The type specimen supporting the reinstated name was collected in the Sambirano River basin in 1909. It is currently preserved at the National Museum of Natural History in Paris.
Baobabs of Madagascar: (A) Approximate ranges of the endemic species, with analyzed samples indicated by colored dots. Asterisks identify individuals that may have hybrid origins based on intermediate morphological characteristics. (B) Flowers and fruits of Madagascar’s baobab species. (C) A possible Adansonia za × Adansonia perrieri individual. (D) A putative Adansonia rubrostipa × Adansonia madagascariensis individual. Image credit: Karimi et al., doi: 10.1002/tax.70176.
“Although Adansonia za shares some physical characteristics with species that were classified later, it is more closely related to two other groups from northern Madagascar than to the species with which it was previously considered synonymous,” Dr. Karimi said.
Adansonia za occurs in the relatively humid Sambirano River region of Antsiranana Province in northwestern Madagascar.
Additional populations may be found farther south, near Marofanderia and on the western slopes of the Manongarivo massif.
“It is remarkable that we are still resolving fundamental questions about Madagascar’s baobabs, including how many species actually exist on the island,” Dr. Karimi said.
Adansonia za is likely to be classified as an endangered species under global conservation guidelines. Its habitat is threatened by extensive deforestation in the Sambirano basin, where land is cleared for cocoa plantations and slash-and-burn rice cultivation.
“Given its current threats and restricted population size, this taxon qualifies as endangered under the guidelines of the IUCN Red List,” the authors said.
The team’s findings were published on July 12 in the journal Taxon.
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Nisa Karimi et al. 2026. Phylogenetic analysis of Madagascar baobabs reveals mixed populations and supports the resurgence of a previously described species. Taxon 75 (4): e70176; doi: 10.1002/tax.70176
Source: www.sci.news