XVI International Botanical Congess

The striking variability in the submerged, floating and aerial leaves of aquatic plants is considered a paradigmatic example of adaptive plasticity. Yet there exist few studies of heterophylly in natural populations. Developmental and physiological research has thoroughly characterized the responses of many heterophyllous taxa to several environmental factors. We present results from an ongoing field study focussed upon the adaptive significance of this trait in three sympatric species of Proserpinaca. Comparisons of biomass and heterophylly in these taxa reveal an inverse correlation at lower total biomass, and a positive correlation at higher biomass. This suggests a threshold, above which heterophylly may be advantageous and below which it may carry a cost. The trend, evident at small spatial scales, suggests fine-grained environmental heterogeneity.