Variability of the three parameters considered describing parental investment amongst populations: a egg number b egg volume; c total investment (i.e. egg number × egg volume). Red boxplots represent crayfish presence in the original ponds, while blue boxplots represent crayfish-free sites. N = 50 clutches. For data analysis, the number of eggs and total investment were logarithm transformed to improve normality; therefore, we show the log-transformed y-axis.