Does FDS by pollinators retard floral evolution in rewarding plant populations by putting rare, novel morphs at a disadvantage? I suggest that only where pollinator visits are rare and reproductive success is pollinator-limited will such a disadvantage handicap the spread of a novel mutant. In other cases, pollinator bias for particular colors, and effects such as differences in nectar production, will be more important in determining whether a novel morph spreads. Where pollinator visitation rates are high, negative FDS may be exerted through selection on selfing rates and male function. To test these hypotheses, we need experiments that vary overall visitation rates and assess relative reproductive success.
Does FDS maintain floral polymorphisms in unrewarding plant species? Both behavioral and field data suggest that it does. We need further experiments to distinguish negative FDS from non-specific mimicry as the agent for the maintenance of the high levels of floral diversity found in unrewarding plant species (Heinrich 1975; Cropper & Calder 1990).
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