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Baldwin et al. (1997) artificially enhanced benzyl acetone emissions in a wild tobacco (Nicotiana attenuata), anticipating increased hawkmoth attraction. Instead, they observed elevated ovule destruction by hemipteran predators (Fig. 5.3). The risks of advertising to natural enemies could counter pollinator-mediated directional selection on fragrance and other floral attractants (Brody 1997). Alternatively, fragrance variation may be non-adaptive in many cases, and...

Through pollinatorplant interactions

I argued above that variation in predation risk among seasons and times of day may affect pollinators' activity. This in turn could have selected for changes in flowering times. For example, selection for early activity by bumble bees (driven by lesser activity of conopid parasitoids) may have selected for earlier blooming of bumble bee flowers. Similarly, the dusk activity of moths may have selected for flowers that open and secrete nectar at dusk. If predation rates do vary among plant...