Fire, bees, and seed production in a mediterranean key species salvia fruticosa miller (lamiaceae)

The typical Mediterranean phrygana has a very rich biodiversity of plants and of solitary bees. Fire may kill the brood of soil-nesting and other solitary bees and may affect pollen and nectar sources. Such changes would be expected to influence seed production in populations of post-fire obligate seeder species and thus also their population dynamics. We compared nectar standing crop, flower visitation rate of bumble bees and solitary bees, and consequent seed production in a typical Mediterranean shrub (Salvia fruticosa Miller) growing in unburned east Mediterranean phrygana vegetation and in an adjacent burned area. The volume of nectar standing crop in the burned area was higher than in the unburned area, while the nectar concentration showed the opposite trend. The mean frequency of Bombus' visits was higher in the burned area, while solitary bees visited flowers only in the unburned habitats. The seed production of S. fruticosa was significantly lower in the burned area. This reduction might have a long-term effect on post-fire species composition and abundance due to the fact that this species is an obligate post-fire seeder. The present evidence indicates that the bee-dependent pollination environment was not re-balanced even six years after fire. This situation has important implications concerning plant species and their bee pollinator diversity.