Many flower traits are specifically attractive to a certain type of pollinator. for example, the scent of rotting flesh is attractive to certain flies and beetles, but not to most other pollinators. what adaptive purpose is served by this kind of "niche marketing" of flowers to specific pollinators?

Every insect pollinator is adapted to deliver the pollen from anther of the male flower to the stigma of the female flower.  

This adaptation is very essential in pollination of flowers. If new pollinators are used then the pollen will be delivered to the stigma of a different species which may lead to only cross pollination.

If this niche marketing of the flower to specific pollinators is not present then fruits of the same species will not form. Each plant species has a selective pollinators based on the floral scent.

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