Discussion

The results for experiment 1 were somewhat surprising. As expected, the data suggest
that different substrates did affect the survival of the guppies. However, one perplexing result is
that the vegetative substrate had the smallest average increase in spot brightness. It seems logical
that the vegetative substrate would provide ample hiding places for guppies, and thus spot
brightness would not be so ill favored due to predation. Additionally, spot brightness increased
substantially in the sandy substrate tank. This seems odd because this environment would not
provide abundant hiding places, unless guppies were to burrow under the sand. Finally, the
muddy tank had the largest increase in spot brightness. This is likely because the mud prevented
predation and allowed spot brightness to increase over time.

The results for experiment 2 were as expected, and strongly support the hypothesis. In the
experiment there were 5 various levels of predation tested. All the data show that as predation
increases, spot brightness will decrease over time. This is because the guppies with elaborate
colors are more apt to attract predators, thus high spot brightness results in a lower fitness. For
the first four levels of predation, the spot brightness still increased. However, the net increase
became smaller as predation increased. Finally, with enough predators present, the spot
brightness decreased. This is likely because the effects of predation on fitness were stronger than
those of sexual selection. Without predation, the data show that spot brightness should increase
substantially over time, due to sexual selection. Therefore, the guppies unknowing play a fitness
balancing game between higher predation and more potential mates.