• Iris pumila;
  • life-history traits;
  • size–number relationships;
  • trade-offs


In current quantitative genetic models, the trade-off is viewed as a dynamic relationship between competing fitness components, which will evolve as a consequence of selection. Selection can change both the intercept and slope of the trade-off function, although it changes the former more strongly than the latter. We tested these predictions by examining two relationships among three clonal life-history traits (ramet number per plant and ramet production rate as a function of leaf number per ramet) in Iris pumila plants originating from an open and a shaded habitat. Our results support the hypothesis that the trade-off function will vary over environments, but not the expectation that the changes in the intercept are more likely than in the slope.