Flower age increases male but not female performance through resource availability in a floral oil-producing species.

Abstract

The high costs of floral maintenance modulate floral longevity. In some species with massive flowering and long floral lifespan, floral longevity increases overall display by changing petal colour, which ultimately counterbalances costs of floral maintenance. However, the colour of petals remains unchanged throughout the floral lifespan in some species with long floral longevity, and the reproductive consequences of such combined traits remain elusive. In this study, we investigated how flower age affects resource availability and reproduction in Stigmaphyllon paralias A. Juss. (Malpighiaceae), a floral oil-producing species in which petal colour does not change throughout its two-day longevity. We quantified petal colour properties (spectral purity, brightness, chromatic contrast with the background, and saturation), resource availability for pollinators, and female and male reproductive performances over the lifespan of 180 flowers exposed or isolated from pollinators. Despite petal saturation decreasing throughout the floral lifespan, the colour hexagon model predicts no perceptual colour change in flowers isolated or exposed to bee pollinators. However, pollen release and oil loss increase over the floral lifespan, while the amount of pollen on stigmas did not change. These results suggest that the maintenance of floral colour in the vision of bees may be related to increased male performance.