Natural selection occurs when nature selects the fittest individuals based on their ability to survive and reproduce. Natural selection is the major force for change in the gene frequencies of a population that leads to evolution. The goal of this research is to compare parametric and non-parametric methods of analyzing phenotypic selection. By comparing the published results derived by the parametric method of analysis (Arnold and Wade, 1984; Lande and Arnold, 1983) with the non-parametric analysis of the same data (Schluter, 1988), the results derived from both methods of analysis can be compared to see if they yield similar (or different) descriptions of natural selection. Because the parametric method requires a quadratic model to describe the quantitative relationship between phenotype and fitness, it can only be used to describe natural selection for data appropriate to this model. In contrast, the non-parametric method of analysis is a regression method that does not require a prior model for the quantitative relationship between aspects of an organism’s behavior or appearance and its survival or reproduction. This research will be done using published data where natural selection was analyzed using the parametric method of selection analysis developed by Stevan J. Arnold, Michael J. Wade, and Russell Lande (Arnold and Wade, 1984; Lande and Arnold, 1983). These summary data will be reanalyzed with the non-parametric method of analysis developed by Dolph Schluter (Schluter, 1988). I will summarize the results from the two methods of analysis to determine if similar (or different) functions describing natural selection were produced by two independent methods of analysis.

Key words: non-parametric, parametric, phenotypic selection, univariate analysis