Pollination and breeding system of Putoria calabrica (Rubiaceae), a Mediterranean dwarf shrub

The pollinator spectrum and the reproductive system of Putoria colabrica, a Mediterranean chamaephyte, were studied. Its flowers are markedly protandr ous and the situation of the style with respect to the stamens can be descr ibed as approach herkogamy, In the male phase, the 4 lobes of the corolla a re completely extended, but in the female, they are curved back, significan tly decreasing the size of the corolla. The volume and sugar content of the nectar were similar between phases, with the concentration being slightly higher in the female phase (41.9% versus 34.5%). Putoria calabrica is total ly self-compatible; the pollen, both the plant's own and from outside, emit ted pollen tubes that reached the ovules within 48 h, and the percentages o f fruit set from both types of pollination were high and similar, Diurnal a nd nocturnal pollinators originated 48.95% and 15.2% of fruit set, respecti vely, while fruit set from free pollination was similar to the sum of the f ormer two. Diptera (mainly Bombyliidae) and Lepidoptera were the most impor tant pollinators, visiting a high number of flowers per plant, The role of protandry and morphological changes of the corolla of Putoria calabrica in its reproductive success are discussed.