The co-optimization of floral display and nectar reward

In most insect-pollinated flowers, pollinators cannot detect the presence of nectar without entering the flower. Therefore, flowers may cheat by not producing nectar and may still get pollinated. Earlier studies supported this 'cheater flower' hypothesis and suggested that the cost saving by cheater flowers could be the most predominant selective force in the evolution of nectarless flowers. Previous models as well as empirical studies have addressed the problem of optimizing the proportion of nectarless and nectarful flowers. However, there has been no attempt to optimize the investment in nectar production along with that in floral display. One of the key questions that arises is whether the floral display will evolve to be an honest indicator of nectar reward. We use a mathematical model to cooptimize the investments in nectar and floral display in order to achieve maximum reproductive success. The model assumes that pollinators rely on a relative rather than an absolute judgement of reward. A conspicuous floral display attracts naive pollinators on the one hand and enhances pollinator learning on the other. We show that under these assumptions, plant-pollinator co-evolution leads to honest signalling, i.e. a positive correlation between display and reward

Clustering of personality traits based on the similarity matrix (table 2): Four distinct clusters emerged using the significance level of individual pair (alpha = 0.05) as the cut-off.

<p>The four clusters were dominated by different body forms as shown in the pie-charts.</p

The six body forms used in the study: Three types of body forms were as shown in columns.

<p>1. Lean (<i>L</i> - narrow shoulders, thin torso and extremities, knee and elbow joints thicker than thy and arm diameter). 2. Muscular (<i>M</i> – Broad shoulders, curved extremities, chest and abdominal muscles shown, thy and arm diameters greater than knee and elbow joints). 3. Slightly fat and feminine (<i>F</i> – rounded shoulders, cylindrical extremities). Each of the three body forms was represented with (designated by +) and without (−) abdominal obesity as shown in rows. The sequence of these figures was randomized during the test and the figures were labeled serially by alphabets.</p

Similarity matrix of all traits based on common choices of figures by respondents: bold face indicates significant positive and underlines negative association

<p>Similarity matrix of all traits based on common choices of figures by respondents: bold face indicates significant positive and underlines negative association</p

Predominant positive and negative associations of personality traits with different body forms:

<p>Both body form and abdominal obesity appear to contribute to the judgment. For most of the traits chi square test for independence is non-significant indicating that the contributions of body form and abdominal obesity are independent of each other. Significance level α = 0.0001</p