Morphological and allometric variation due to percentage of cover in Eichhornia azurea (Swart) Kunth (Pontederiaceae)

Exploring the density-dependence theory is crucial to understanding how size patterns among individuals are established. This study tested if percent cover affects the morphological and allometric relationship variation of individuals of Eichhornia azurea (Swart) Kunth, an emergent perennial mat-forming macrophyte commonly found in the lower Amazon region. We predicted that (1) E. azurea found in sites with high percent coverage would have larger, thicker, heavier leaves and longer petioles than individuals found in sites with low percent coverage; (2) the percent coverage affects the allometric relationship between branch length and number of leaves. To test our predictions, we sampled sites with low and high E. azurea percent cover. Sampling occurred in Caxiuanã Bay located in Caxiuanã National Forest on the lower Amazon. The results supported our predictions, in which individuals of high percent cover sites had longer petioles, more leaves, thicker leaves and higher leaf mass per area. Individuals in low percent cover sites showed a positive relationship between branch length and number of leaves. These results indicate that E. azurea exhibits morphological and allometric plasticity in response to plant density which may help explain the success of E. azurea in a variety of habitats across South America.