Ecologists traditionally emphasize niche differences when explaining species coexistence. However, if niches are similar, minimizing ecological fitness differences can allow for coexistence. Selection pressures due to competition could therefore result in changes in niches or ecological fitness of species, thereby changing competitive outcomes. However, the interactions between the evolution of niche and fitness are not well understood. I used a response surface design to estimate niche and fitness differences between pairs of protists in the lab. Then, after approximately 50 generations of growth in competition, I redetermined the niche and fitness differences to quantify changes due to selection.
Results/Conclusions
Preliminary results suggest that evolution causes large changes in the fitness differences between species relative to changes in niche differences. In fact, niche differences tended to not change or decrease. These changes had consequences for the coexistence of species, and sometimes, a switch in competitive dominance. These results are unexpected since in most cases, models of evolution in competition suggest species will increase niche differences and therefore coexistence.