Pollination Relationships in Southern Spanish Mediterranean Shrublands

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Abstract
(1) Pollination relationships were investigated for fourteen months in a southern Spanish Mediterranean coastal scrub community, composed of thirty plant species, at Reserva Biologica De Donana, Donana National Park. (2) Flowering encompassed the whole year, as did insect visits to flowers. Distinct seasonal changes, however , in both the number and identity of insect taxa, and in the number of plant species in bloom were apparent: maximum plant and insect richness occurred in spring. (3) Insect visitors mainly included small bettles, honeybees, small halictid bees, syrphids and bombylids. The overall species richness of the pollinator array was very high (187 taxa). (4) Plant species with specialized pollination mechanisms were relatively infrequent. Most plants had non-restrictive or small flowers, or both. Species relying on pollen to attract pollinator outweighed those relying on nectar as the main reward. (5) Joint analysis of flower attributes, blooming phenology and pollination vectors demonstrated that species flowering at about the same time of year tend to have their flowers visited by the same insects, irrespective of floral features. (6) It is hypothesized that fruit set is more resource- than pollen-limited and that to achieve maximum fruit set most plants have unspecialized pollination relationships. The generalized nature of pollination systems may have been a major factor contributing to the survival and weedy behavior of many mediterranean scrub species.