NEGATIVE FREQUENCY-DEPENDENT SELECTION BY POLLINATORS ON ARTIFICIAL FLOWERS WITHOUT REWARDS.

Area of Science:

• Ecology
• Evolutionary Biology
• Behavioral Ecology

Background:

• Many nonmodel orchids exhibit corolla color polymorphism, pollinated by naive insects seeking nectar without mimicry.
• Stable polymorphisms suggest negative frequency-dependent selection, potentially driven by pollinator foraging behavior during avoidance learning.

Purpose of the Study:

• To experimentally test if pollinator behavior leads to a preference for rare color morphs in deceptive plant species.
• To investigate the role of pollinator foraging strategies in maintaining plant color polymorphisms.

Main Methods:

• Laboratory experiments using artificial flowers with varying color morph frequencies and reward presence (sucrose solution).
• Observing bumblebee (Bombus terrestris) foraging preferences on rewarded and unrewarded artificial flower arrays.
• Analyzing bumblebee visitation patterns to assess preferences for common versus rare morphs and inter-morph movement.

Main Results:

• Bumblebees preferred common color morphs when flowers offered sucrose rewards.
• When flowers lacked rewards, bumblebees overvisited rare morphs and moved between unrewarding, unlike color morphs.
• This suggests a probabilistic sampling strategy in unrewarded foraging.

Conclusions:

• Pollinator behavior, specifically overvisiting rare morphs when unrewarded, can create a selective advantage for rare morphs.
• This behavior induces negative frequency-dependent selection, supporting the maintenance of stable corolla color polymorphisms in deceptive, non-mimicking plant species.