AUTHOR=Aguiar João Marcelo Robazzi Bignelli Valente , Maciel Artur Antunes , Santana Pamela Cristina , Telles Francismeire Jane , Bergamo Pedro Joaquim , Oliveira Paulo Eugênio , Brito Vinicius Lourenço Garcia 

TITLE=Intrafloral Color Modularity in a Bee-Pollinated Orchid

JOURNAL=Frontiers in Plant Science

VOLUME=Volume 11 - 2020

YEAR=2020

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2020.589300

DOI=10.3389/fpls.2020.589300

ISSN=1664-462X

ABSTRACT=Flower color has been studied in different ecological levels of organization, from individuals to communities. However, it is unclear how color is structured at the intrafloral level. In bee-pollinated flowers, the unidirectional gradient in color purity and pollen mimicry are two common processes to explain intrafloral color patterns. Considering that floral traits are often integrated, usually reflecting evolutionary modules under pollinator-mediated selection, we hypothesize that such intrafloral color patterns are structured by intrafloral color modules. Here, we studied the tropical bee-pollinated orchid Cattleya walkeriana, given its intrafloral color complexity and variation among individuals. We investigated if intrafloral color modules arose among intrafloral patches (tip or base of the sepals, petals, and labellum). We expected a separate color module between the labellum patches (the main attractive structure in orchids), i.e. varying independently among individuals in relation to petals and sepals. We measured the color reflectance and calculated the spectral purity, hue, and the chromatic contrast of the floral structures. Spectral purity (saturation) was higher in the labellum tip in comparison to petals and sepals, generating a unidirectional gradient. Labellum base presented a less saturated yellow UV-absorbing patch, which may reflect a pollen mimicry strategy. The colors of tips and bases of petals and sepals were strongly correlated among individuals, forming a module, and weakly correlated with the tip of the labellum. There was no correlation between the color of the labellum base and any other floral patch. The color modules were unrelated to the development of floral whorls since the color of petals and sepals were integrated, while the labellum showed two different color modules. Given the importance of intrafloral color patterns in bee attraction and guidance, our results suggest that intrafloral patterns could be the outcome of evolutionary color modularization under pollinator-mediated selection.