Format: ORAL

Melissa Len-Osper1, M Luisa Buide1, Montserrat Arista2, Pedro L. Ortiz-Ballesteros2, Justen B. Whittall, Jos C. del Valle2, Eduardo Narbona1.

1 Pablo de Olavide University, Seville, Spain. 2 University of Seville, Seville, Spain. 3 Santa Clara University, Santa Clara, USA.

The evolution of flower color is commonly shaped by selective pressures exerted by pollinators. The sensory drive theory posits that the evolution of communication signals is determined by the sensory systems of the animals and the habitat conditions in which the signals are received. When applied to pollinators, this theory would imply that some floral colors may have divergently evolved in certain light environments, for example by becoming more conspicuous. Using the Mediterranean vegetation of south Spain, we compared flower color of coastal dune vegetation with open light environment and sandy background with those of closed cork-oak forest with shaded light environment and green leafy background. We hypothesized that, in the visual system of bees, each vegetation should be highly conspicuous in its own light environment and background. Irradiance of each community, reflectance spectra of flowered species and sandy dunes background were collected. We modelled these data in the visual system of bees to assess conspicuousness differences of each flower community under different light environments.We found that the irradiance of coastal dune with open light environment was four orders higher than light reaching the cork-oak understory and showed differences in the spectral shape. Furthermore, sandy background nearly doubles the reflectance compared to leafy backgrounds, also showing spectral shape differences. In each vegetation type, we categorized flower color as UV+ yellow, UV- yellow, pink and white. In both communities, all flower colors but UV- yellow showed significantly higher chromatic contrast in the dunes environment that in the corn oak understory.However, UV- yellow flowers showed lower in these conditions. Taken together, our findings indicate that open sandy environments favor the conspicuousness of mostflower colors and suggests that other selective forces may play a role in theevolution of flower color at the community level.