OCR Text |
Show FAW had to consume more grass to receive the same amount of nutrients or (2) the chemicals from the fungus made it harder for the FAW to assimilate the grass. When looking at data from the above experiment, we were struck by the difference in water loss between the E+ and E- grass. We then devised an experiment to establish the water loss difference between the two types of grass. We cut each type of grass at week long intervals, weighed it and dried it for approximately one month. After the grass was completely dry, we weighed it again and calculated the water loss. We found that both types of grass lost roughly the same amount of water. Data from the first experiment lea us to believe that E+ grass lost its water more slowly therefore, the E+ grass probably contained more water during the three day period We also ran a wasp grass preference test to see if wasps interact differently with the two types of grass. Providing uniform light within the cage, we placed three petri dishes containing either E+ grass, E- grass or no grass in the cage. Over a period of three hours we counted at regular intervals how many wasps were attracted to each dish. We found that the wasps preferred E- grass, but it appeared to be a learned behavior since, after parasitizing FAW on E+ grass, the wasps then showed a preference for E+ grass. If the wasps do in fact prefer E- grass then the E+ grass would have less regulation of herbivores by wasps. If so, we can conclude that the fungus/grass association is not mutualistic since the wasps were more likely to contact FAW on E- grass. Finally, we were able to draw the conclusion that, in a two level system the grass/fungal association was beneficial for the producer because it had a negative effect on the herbivore. Preliminary data indicates that this relationship may not be true when the effects on the parasitoid are considered. If the parasitoid is not attracted to the E+ grass, then the grass will suffer greater negative effects from herbivory. Mathematically, our model tells us that the most important parameters involve the association between the producer and the parasitoid. |