Improved flower advertisement, pollinator rewards and seed yield by enhanced UV-B radiation in the Mediterranean annual Malcolmia maritima

The effects of enhanced UV-B radiation on reproductive and pollination success were investigated in the Mediterranean annual Malcolmia maritima. Plants were exposed in the field to ambient or ambient plus supplemental UV-B radiation (biologically equivalent to a 15% ozone depletion over Patras, Greece, 38°14' N, 21°44' E) up to leaf senescence and fruit maturation. UV-B radiation had no effect on stem and fruit biomass, anthesis time and duration and flower number. However, flower diameter, nectary volume and nectar amount per flower (but not nectar concentration) were significantly increased by supplemental UV-B radiation. In addition UV-B treated plants showed higher reproductive success (i.e. lower abortion rates and higher fruit to flower ratio) and a trend to higher pollination success (i.e. increased number of seeds per fruit). As a result, the seed yield was increased. Seed mass, seed germination and early seedling growth were not affected by UV-B treatment of mother plants. It is suggested that the UV-B induced changes in flower attributes might have affected pollinators' behaviour in a way that improved the fitness of M. maritima.