There is no ecosystem in which the organism lives independently, biological interaction occur at all levels and in different ways. They can be beneficial or prejudicial for the organism involved. During the second week of the course we had the opportunity to learn more about these interactions by the hand of Allen Herre, a specialist in the relationship between a tiny wasp and the figs and Hermógenes Fernández, who study the mutualistic symbiosis between leaf-cutter ants and their fungal.
If you ask me, who invented the agriculture, I have to answer that the leaf-cutter ants (genus Atta) do it! These ants live in an obligated symbiosis with a fungus that they grow to eat. The ants collect pieces of leaves from the forest, take it to the nest underground and use them as a substrate to grow the fungus; and, just as we do with our crops, they take care of the fungus, they use their own feces to fertilize it and produce their own antibiotic to protect them from other pathogens fungus. This is a beautiful example of mutualism and coevolution, where the surveillance of one species depends of the other one.
But not everything is perfect in the world of the mutualism, there are cheaters, and some host learned how to sanction the cheaters. This is the case of the the fig tree – fig wasp species. Both species are dependents for the reproduction success; the fig wasp can only oviposit and reproduce in the flowers of the fig, in reward the wasp have to pollinate the flowers of the fig. But, when the wasps do not pollinate the flowers the fig sanction the wasp aborting the fruit.
Jandér, K.Ch. and E. A. Herre. 2010. Host sanctio ns and pollinator cheating in the fig tree – fig wasp mutualism. Proc. R. Soc. B . 277, 1481–1488