Article

In this work, the pollination effectiveness in two populations of Antirrhinum microphyllum, endemie to Centrai Spain, were investigated. The mean number of flowers per plant (54) and the percentage offlowers that produced seeds was high at both locations (84% and 92%). The fiorai advertisements (ultraviolet pattem) and rewards (volume and sugar concentration ofnectar), and pollinators were al so studied. The flowers produced an average of3 !-lI neclar with 40- 45% sugar. The most frequent flower visitor was a solitary bee, Rhodanthidium sticticum. II is active only on sunny days between 9 a. m. and 4 p. m., solar time, with a maximum between II a. m. and 1 p. m. The percentage of flowers visited per day in a pIanI ranged from 6-24%. The behaviour of nectar-collecting is described. The results indicate that the narrow distribution of this species cannot be explained by factors linked to the pollination processo