Chromatic exclusivity hypothesis and the physical basis of floral color

Abstract

This paper presents the results of floral spectral studies on 1275 flowers from India, Brazil, Israel, Germany, and Norway. Floral spectral reflectance from 400 to 700 nm (nm) was used to quantitatively represent ‘human-perceived’ color of flowers in Red, Green, Blue color space. Floral spectral reflectance from 350 to 600 nm was used to discern and objectively represent ‘insect pollinator-perceived’ flower colors in color hexagon. We leverage the advantage offered by ‘quantified human perception’ provided by ‘human-perceived’ floral colors to represent the distribution of floral hues and uncover the relationship between the composition of incoming solar radiation and predominant ‘human-perceived’ floral colors at the tropics and the higher latitudes. Further, the observed species-level mutual exclusivity of ‘insect pollinator-perceived’ floral colors is stated as chromatic exclusivity hypothesis. We compare ‘human-perceived’ and ‘insect pollinator-perceived’ floral colors at Trivandrum (India) and provide a physical explanation for short and long ‘wavelength triads’ of insect pollinator and human visual sensitivity respectively.