Mutualism Is More Than Just Two Species Working Together

Wiki Commons Jan Celliers Park

I found this particular article interesting to show how mutualism expands beyond an interaction between two species.  There are complex connections throughout nature that hold together well established systems.  Upsetting any one factor can throw the whole system out of balance, causing ripples in the population dynamics of all species involved.

In this case, fig wasps lay their eggs in the seed ovules of the fig.  The larvae feed on the seeds so for every wasp larvae, one seed is lost.  However, the wasps fertilize and disperse the pollen of the fig so it is advantageous for them to sacrifice some seeds in order to pass on their genes.

It becomes obvious that the wasps could potentially take up all the seeds and put the trees genetic heritage at risk.  In comes another parasitic wasp which preys on the pollinator wasp.  The parasitic wasp injects its eggs directly through the fruit into the ovule.  Their larvae then feed on the pollinator wasp larvae.  The effect of this is that the pollinator wasps tend to concentrate their egg laying in the middle of the fruit, where the parasitic wasp cannot reach.  In the well protected interior of the fruit, the larvae are safe from parasites and can complete their life cycle.  

The result is that the outer ovules are safe from the pollinator parasites and those seeds are able to mature and pass on the trees genetics.  The tree needs BOTH wasp species to maintain a balance.  Even this scenario is an oversimplification.  There are probably other species and environmental factors that come into play here as well.  Upsetting any part of this and you will no doubt develop a pest problem.  The population of all species in the system needs to remain stable for it to work correctly.

These are the types of interactions that begin to take place in a well established food forest or garden.  It is important that increasing biodiversity and stability be maintained in order for these mutualistic interactions to develop.  If you eliminate any one species, the consequences could be profound and you may end up running counter productive to the overall productivity of your system.  It is impossible to actively control the population of undesirable garden species without affecting their natural biological controls....  and the species they are connected to.... and the species connected to them...

If you diminish the biological control, they cannot be effective when the prey species rebounds.  Complicated biological controls often take longer to develop and stabilize than the species they prey on.  This leaves the system vulnerable in the meantime.  If you take matters into your own hands, you become responsible for the control of that pest species forever more.  The system becomes addicted to that response.  In this respect,  even organic control measures have a profoundly disruptive effect.