B

Low density

Low density

High density m

Fig. 14.2. Predicted relationships between floral display size (F) and (A) pollinator visitation rate per plant (Vp), and (B) the number of flowers probed per plant (tc). (Adapted from Ohashi & Yahara 1999.)

High density m

Floral display size(F)

Fig. 14.2. Predicted relationships between floral display size (F) and (A) pollinator visitation rate per plant (Vp), and (B) the number of flowers probed per plant (tc). (Adapted from Ohashi & Yahara 1999.)

populations usually include plants of various sizes (e.g., Pleasants & Zimmerman 1990). In such populations, pollinators prefer to visit large floral displays over smaller ones (Fig. 14.1A; Table 14.1).

Two major hypotheses have been proposed to account for the observed preference for large floral displays: (1) the detection-advertising hypothesis; (2) the flight-cost hypothesis. The detection-advertising hypothesis states that floral display size limits the distance from which it could be detected because of the insects' limited visual resolution (Dafni et al. 1997). For example, Giurfa et al. (1996) showed that the minimum display

"cC 100

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