Flower Size and Shape: Implications in Pollination

In 42 plant species, the flowers' en face planar projected areas, contour lengths, and the ratios between them (= contour densities) were measured in relation to their pollinators, type of reward, and flower shape. A significant correlation exists between the planar projected area and contour density, which indicates that small flowers have broken outlines. Beetles were found to be associated more with large, rounded (bowl-shaped) flowers. Small bees, in contrast to medium and large bees, were associated significantly more with small flowers having broken outlines (i.e., high contour densities). Each factor examined (pollinator, flower shape, and reward) and each possible interaction among them, is significantly related to the values of each morphological variable. This implies that each category of pollinator (beetles, small, and medium-large bees) is associated with a syndrome of dependent floral characteristics (size, shape, and reward). We propose that the greater contour density of smaller flowers compensates for their smaller size by increasing visibility and the broken outline shapes act as “form guides” in the orientation, landing, and foraging by pollinators of flowers.