Irvingia Gabonensis: The Dika Diet
Nomenclatural History
This is a specilized species with many, many, many names. Just a few can be seen below.
- Indigenous Names (people/country : local name): Hausa: Agbalo; Nigeria: oro, oba, abesebuo, goron biri, moupiki, muiba, eniok, andok; Ibo: ogbono (kernels); Afemai (Edo State of Nigeria): ogi (fruit of I. gabonensis); Yoruba: apon; Cameroon: andok; Batanga (language in prime dika country near Kribi, Cameroon): mbumbwe’bo, nja’a; Congo: meba, mueba; Cwondo: Aadok; Ny: Abisibou; Kiaka: Aiya iyon; Mvae: Ando; Bulu (or Boulou): Ando’o; Bolon, Fang, Gabon: Andok; Temne: An-Gbere; Akyé: Bè; Mende: Boboi; Bateke: Boubwé; Dogose: Bwiba bambale.
- Common Names (people/country : local name): Sierra Leone: bobo; Côte d’Ivoire: boboru, wanini; English: bush mango, wild mango, dika, dika nut; French: manguier sauvage, chocolatier
- Linnaean binomial: Irvingia barteri Hook.f, Irvingia caerulea Tiegh., Irvingia duparquetii Tiegh., Irvingia erecta Tiegh., Irvingia fusca Tiegh., Irvingia griffonii Tiegh., Irvingia hookeriana Tiegh., Irvingia laeta Tiegh., Irvingia pauciflora Tiegh., Irvingia platycarpa Tiegh., Irvingia tenuifolia Hook.f., Irvingia velutina Tiegh.
Evolutionary History
Locally, the different irvingia fruits are often referred to as payo in general. There are differences among them, but there is not much historical information on the evolution of these species. However, it is known now that these relatives speciated in “diversity ‘hot spots” (Lowe et al., 2000). These are zones in which there is high genetic diversity within these similar species.
This range is mainly contained to west-Central Africa. Countries included are Ghana, Nigeria, Cameroon, and Gabon being the main locations in which they are found (Leaky, 2017). However, in Cameroon is thought to be where this center of genetic diversity originates from (Leaky, 2017).
This is thought to be caused by the Pleistocene refugia dynamics. In simpler terms, there has not been a large influence of climate change since the Pleistocene era.
This means there has been a relatively constant environment, leading to species having relatively similar attributes due to them being the best adaptations for fitness (Lowe et al., 2000). They are varied just slightly enough to allow for niche partitioning and stable distribution. The main difference between our species and those that are closely related to it is that Irvingia gabonensis fruit is sweet and fleshy, while its relatives’ fruits are bitter and inedible (PROTA4U, 2017).
Ecology & Life History
This species is an important food source for many animals in the forest. The mammals of central Africa find this to be extremely nutritious. These mammals include a diversity of species including forest elephants, squirrels, red forest pigs, etc (Ainge & Brown, 2001). This is due to the seeds of the dika fruit being high in nutrients such as lipids and fats. Gorillas find the fruit itself to be their favorite part of the plant. Lastly, bees thoroughly enjoy the nectar of the flower and find it necessary in their production of honey (Ainge & Brown, 2001).
That being said, insects are the most important pollinator of this plant. The plant itself flowers twice a year, so there is plenty of time for pollination season. There are two obvious peaks of flowering, the height of the dry season in January, and the wet season in October (Ainge & Brown, 2001).
However, the fruiting time of this plant is less variable, with there being a range of fruiting twice a year, in accordance with the flowering times, all the way to slowing down to fruiting once every two years (Ainge & Brown, 2001). However, the trees begin flowering after reaching maturity. This usually takes about ten to fifteen years, but sometimes they can begin to bloom as early as six years old (Ainge & Brown, 2001).
Morphological Description of Vegetative Attributes
In general, this species is very large. They grow up to 40 meters tall, and have a meter wide buttresses that grow to nearly 3 meters high (PROTA4U, 2017). The bark is scaly and heartwood soft, with both being a green-yellow to gray. Also, the inner bark is fibrous and of an intense yellow (PROTA4U, 2017). Not only are there different textures throughout the wood, it is also quite dense, making them prone to shrinkage.The leaves themselves are simple, elliptical, leathery, thin, pinnately veined, and alternate up the stem (PROTA4U, 2017).
There is a possibility that they can be propagated vegetatively, especially for those that want to create communities of trees with favorable phenotypes (ie bigger fruits) (Leakey, 2017). However, there are limits on the age of the actual cuttings able to propagate. This is because while juvenile cuttings tend to be able to grow and provide a large amount of fruits, when the shoots are already mature, it is harder for them to mature even more into full trees and provide a similar amount of fruits as the juvenile cuttings (Leakey, 2017).
