At the Great Rift Valley lodge the Acacia drepanolobium is a common plant. Its thorn-filled branches have evolved over the millennia to avoid being browsed on by the giraffe which evolved to have prehensile tongues to be able to pick acacia leaves between the thorns. The A. drepanolobium, went one step further and evolved to have galls on the edge of the thorn. These galls provide shelter for the cocktail ants which return the favour by protecting the acacia from being browsed on by the giraffes. When the giraffe sticks out its tongue to gather the leaves on the branch, the cocktail ants rush out of the galls and produce an irritant fluid to keep the giraffes at bay.
This is an example of co-evolution where two (or more) species affect each other’s evolution. So for example, an evolutionary change in the morphology of a plant might affect the morphology of the herbivore that eats the plant, which in turn might affect the evolution of the plant, which might affect the evolution of the herbivore…and so on.
This is a case of an exclusive “matches” between a plant and an insect even though pollination is not involved. The hollow thorns are the exclusive nest-site of the ant which drinks acacia’s nectar. The ants are not just taking advantage of the plant but also defending the acacia against the herbivores.
This system is probably the product of coevolution: the plants would not have evolved hollow thorns or nectar pores unless their evolution had been affected by the ants; and the ants would not have evolved herbivore defense behaviors unless their evolution had been affected by the plants.
An Interesting Insect on the ground
Jean Michel Kersaudy from France is a regular guest at the Great Rift Valley Lodge and is researching on the Harvester ant (Messor cephalotes) found on the grounds of the lodge and the golf course, much to the chagrin of the green keepers.
The harvester ant is a huge red colored seed-collecting ant found in East Africa.
The objective of Kersaudy’s research is to identify the type of grazing insects that are laying the golf course bare – in other words contributing to its land degradation. Land degradation in this context is the removal of grass on their trail.
The second objective is to determine the extent to which grazing insects are contributing to golf degradation at GRVL.
The harvester ant species Messor cephalotes use of formic acid produced in their glands to clear the grass.
- After separating the seeds from husks, the ants remove the husks and put them outside their nests.
- They have a queen but no king because the king dies immediately after mating. Mating takes place during the long rain season.