Red flowers differ in shades between pollination systems and across continents

Area of Science:

• Plant-pollinator interactions
• Floral color evolution
• Animal color vision

Background:

• Floral color is a key signal in plant-pollinator relationships.
• Red flowers are often associated with bird pollination, explained by bee avoidance and bird attraction hypotheses.
• The relative importance of these hypotheses, particularly concerning color perception, remains under-investigated.

Purpose of the Study:

• To investigate the role of color perception in red floral signals for birds and bees.
• To compare the conspicuousness of red flowers to different pollinators across continents.
• To test the bee avoidance and bird attraction hypotheses on a large scale.

Main Methods:

• Collected reflectance spectra from 130 red flower species globally.
• Analyzed spectra using color vision models for bees and birds.
• Quantified differences in color conspicuousness and spectral properties.

Main Results:

• Red flowers are highly conspicuous to birds and less so to bees.
• Flowers are more conspicuous to their respective pollinators.
• New World bird-pollinated red flowers show distinct spectral properties, potentially enhancing bee avoidance.
• Secondary reflectance peak (SP) intensity influences chromatic contrast, impacting pollinator attraction.

Conclusions:

• Floral color specialization in red hues influences pollinator interactions.
• Evolutionary shifts in red flower spectral properties may prioritize bee avoidance.
• Specialization is more pronounced in New World bird-pollinated flowers, suggesting regional adaptations.