In my published phylogeny of the moringa family, I tentatively placed Moringa pygmaea as sister to (the closest relative of) Moringa borziana. This decision was based mostly on the report of the flower color of M. pygmaea as being similar to that of M. borziana. I probably could have done better, but this would have involved damaging the only herbarium specimen known of M. pygmaea at the time, and I preferred to make a tentative assignment and let the specimen be while awaiting new collections of the species. These collections did come to light, when in 2004 Mats Thulin, Swedish botanist and author of the Flora of Somalia, took the first photographs ever taken of the plant. His photos show dirty brown reflexed petals, just like Moringa rivae. The similarity between the flowers of M. pygmaea and M. rivae is quite stunning, and strongly suggests that the two species are closely related. The similarity is so strong that the best hypothesis seems to me to be that Moringa pygmaea is sister to M. rivae, that the group made up of these two species are then sister to M. aborea, with M. borziana being sister to the M. arborea-M. rivae-M. pygmaea group. Moringa longituba on gypsum soils in the Somali region is often found growing particularly small, as near Las Anod in Puntland. Instead of the 1-4 meter long stem it has in other areas, these flower and leaf out at ground level, dying back to the underground tuber practically every year. Some have suggested that M. pygmaea is just a similarly dwarfed form of one of the already-described species. But Thulin’s photos show erect fruits, unique in the family. All other Moringa species have hanging fruits, including Moringa rivae. If M. pygmaea were just a dwarf form, then it would be of Moringa rivae, given the similarity in flowers. But erect fruits is exactly what natural selection would favor in a tiny tuberous herb. Pendent fruits would drag on the ground and get thrashed around in the wind, and such individuals would be less reproductively successful than those that have fruits held away from the ground. So this characteristic makes it seem certain that M. pygmaea has been living its tiny lifestyle on Somali silt plains for a very long time and that it’s a quite distinct species.
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AuthorDr. Mark E. Olson is a researcher at Mexico's national university and an expert on the biology of the genus Moringa Archives
November 2018
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