1 In this paper, the effect of flowering synchrony on the reproductive success of Hormathophylla spinosa, a plant living in the Mediterranean high-mountains of the Sierra Nevada (SE Spain), is demonstrated. Eighty plants belonging to three populations were permanently labelled during the period 1988-91, and in each plant the duration and date of flowering as well as the estimated flowering synchrony, were noted. The composition and abundance of the pollinator assemblage, the abundance of the floral herbivores and the effect of the seed and fruit consumers were also recorded. 2 In 1989, 1990 and 1991, the relationship between the flowering synchrony and the three rate-based components of reproductive success (fruit set, brood size and female fertility) were studied. The effect of phenotypic selection on flowering synchrony, as well as on duration and time of flowering, was also studied for these three years, using the method of multiple regression for correlated characters. 3 The flowering synchrony of H. spinosa plants ranged from 0.25 to 1.00, although more than 70% of the marked plants had a flowering synchrony level greater than 0.75. The plants with a lower degree of flowering synchrony were visited by a greater number of pollinators and eaten by fewer herbivores. 4 However, only in 1989 and 1990 was there a significant relationship between flowering synchrony and brood size of the plants. In addition, the phenological traits did not affect female fertility. The results show that neither directional nor stabilizing/disruptive selection acts on flowering synchrony. For these reasons, I suggest that the flowering synchrony of H. spinosa is not regulated by selective pressure of pollinators or herbivores.
