Visual discrimination between two sexually deceptive Ophrys species by a bee pollinator

Area of Science:

• Plant-animal interactions
• Pollination biology
• Orchid reproductive strategies

Background:

• Orchid genus Ophrys utilizes sexual deception for pollination, mimicking female insect sex pheromones.
• Ophrys species primarily attract hymenopteran males, with some species displaying colored perianths and labellum patterns.
• Previous research indicated the pink perianth of Ophrys heldreichii enhances pollinator detectability.

Purpose of the Study:

• To investigate the role of the labellum pattern in Ophrys heldreichii pollination.
• To determine if the labellum pattern mimics the female pollinator to increase attractiveness to males.
• To understand the visual cues guiding pollinator attraction in Ophrys species.

Main Methods:

• Dual-choice tests using Ophrys heldreichii and Ophrys dictynnae flowers presented to Eucera berlandi males.
• Experiments conducted in UV-transmitting acrylic boxes to eliminate olfactory cues.
• Spectral measurements to analyze color contrast and brightness of floral components.

Main Results:

• Eucera berlandi males showed a significant preference for Ophrys heldreichii over Ophrys dictynnae when olfactory cues were excluded.
• When labellum patterns were the only difference, males chose randomly between the two flower stimuli.
• Perianth chromatic contrast, not labellum pattern, influenced initial pollinator approach.

Conclusions:

• Pollinator choice in Ophrys heldreichii is primarily mediated by perianth chromatic contrast during initial attraction.
• The labellum pattern does not appear to influence male attraction but may play a role in post-copulatory aversive learning.
• This suggests a dual strategy for Ophrys orchids, using visual cues for attraction and potentially learned associations for enhanced outcrossing.