Sometimes called the ‘upside-down tree’, the baobab tree is usually identified with the continent of Africa. One species, Adansonia digitata, is wide-spread on the African continent. Another species, Adansonia gibbosa is found in a limited area of Northern Australia. The island of Madagascar has six indigenous species (A. madagascarensis, A. perrieri, A. suarezensis, A. grandidieri, A. rubrostipa, and A. za) as well as the mainland African one.
The obvious question for a biologist is ‘Why?’ Why does the ecologically diverse continent of Africa have only one species while the comparatively small island of Madagascar has six unique species. It is easy to explain the existence of one species in Australia – somehow, probably by ocean currents, a baobab fruit came ashore millennia ago and, isolated from others of its species and exposed to unique selection forces, evolved into a new one. It is easy to explain the existence of A. digitata species in Madagascar; it was almost certainly taken by seafaring traders as it was to many other places, including India. But how did six different species evolve so close to each other in Madagascar? What were the isolating mechanisms that triggered this speciation?
It is a question that has baffled biologists for ages and has kept me musing since I first went to Madagascar in 1974. At that time I was studying the honeybees of Madagascar. (People look at you in a quizzical way when you wander around the market catching bees on the wing and putting them into a little vial – weird foreigners! When the bees suddenly quit coming to collect flour it is time to leave lest you be accused of magic.)
Another issue that has interested me as a community resource planner and an instructor of environmental studies is how to involve the residents of an area in the conservation of species. What are the values, economic or cultural, which would cause people to protect their baobab trees? What is the role of parks and conservation areas in protecting these rare species?
After nine years in Africa, I returned to Canada in 1980 and became tied up as an educator in the academic world. Now retired, I am free to follow up on my baobab fancies again.
There is a lot more information available on baobabs today. We are finally clear on just how many species there are. We have a much better picture of their distribution. Data on their chromosomes give us some clues to their evolutionary beginnings.
In Iate 2011 I will make my third trip to Madagascar. I plan to see all of the baobab species, work with researchers in the country, and post blog updates including photos.
Here is a photo of Sarah and I in 1979 at ‘Le grand baobab’ in Majunga and a photo of some of these marvelous tree in the south of Madagascar.
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