Summary of the associations between aggregation and the seven other life-history traits of Tetrahymena thermophila. Principal component plot representing the associations between the first two component axes and component loading vectors for cell aggregation index g and the seven other life-history traits quantified for the ten T. thermophila strains studied . Vectors that share a similar direction and length suggest traits that are more highly associated among cell strains. For the same reason that replicates of a given strain were not linked between experiments, points on the graph show means of five random associations between replicates of each strain to illustrate both between and within strain variation as in Figure 5. Results on analyses of the 10 strain means were extremely similar and are not shown.