Alternative designs lead to similar performance when traits and performance vary on different axes

Plants differ from one another in size, architecture, water relations, and resource uptake, and these differences often lead to differences in performance. Yet within a community species that differ markedly in these traits often have similar performance. Here we use a simple model to show that when the major axes of trait covariation do not align with the axis of performance variation, large differences among species in structural traits may have similar performance, i.e., ‘alternative designs.’ We further illustrate this phenomenon using trait and performance data from co-occurringProteaspecies in the Cape Floristic Region, South Africa. Long-term coexistence of species within a community requires both similar levels of performance, so that some species are not excluded by competition, and niche differentiation, so that multiple species can coexist. Thus, misalignment between the axis of performance variation and the major axes of trait variation may be common, just as genetic variation may be maintained within a population when the selection gradient does not align with the major axes of the genetic variance-covariance matrix.