“Smart” Nitrogen-Fixing Plants and Evolutionary Game Theory
This article discusses a new theory based on evolutionary game theory that aims to explain a long-standing mystery of why nitrogen-fixing plants grow where they do. Researchers have pondered the question of why nitrogen-fixing plants seem to struggle in ideal conditions while thriving in those that seem disadvantageous. Ecologists would assume that nitrogen-fixing plants would out-compete other plants in areas where the soils had low levels of nitrogen, since they would be the only ones that would be able to convert atmospheric nitrogen into extra fertilizer. Similarly, one would expect nitrogen-fixing plants to do less well in soils with high levels of nitrogen, since they would no longer have much of an advantage over the other plants. The truth, however, is the opposite. Nitrogen-fixing plants are literally overshadowed in areas with high levels of nitrogen in the soil, but they thrive in areas of low nitrogen.
Researchers turned to the evolutionary game theory that was discussed in class to investigate how nitrogen-fixing plants would perform in areas with high levels of nitrogen and low levels of nitrogen. They discovered that in areas of high soil nitrogen with normal plants, it is not evolutionarily stable to be a nitrogen-fixing plant. Nitrogen-fixing plants in these temperate soils constantly generate nitrogen, taxing their growth and allowing the other plants to over take them. In contrast, in nitrogen-rich tropical soils, nitrogen-fixing plants convert nitrogen only early on in their growth but switch it off when there are high levels of nitrogen in the soil. Thus, they can focus most of their energy on growth, successfully competing with the other plants.
The evolutionary game theory model successfully explains the growth pattern of nitrogen-fixing plants in the world.
http://phys.org/news/2015-12-theory-smart-evolution-global-ecosystems.html