EXPERIMENTAL-STUDY OF POLLINATION BY ANTS IN MEDITERRANEAN HIGH-MOUNTAIN AND ARID HABITATS

In this paper, we report the results of an experimental study on ant p ollination of three plant species inhabiting the Mediterranean high mo untains (Alyssum purpureum, Arenaria tetraquetra and Sedum anglicum) a nd four species inhabiting the aridlands (Lepidium subulatum, Gypsophy la struthium, Frankenia thymifolia and Retama sphaerocarpa) of South-e astern Spain. We determined several plant and ant traits, as well as t he composition and abundance of the pollinator assemblage. Insects bel onging to 29 families and five orders visited the flowers of the plant species studied. In all but two, L. subulatum and G. struthium, the a nts comprised 70-100% of the flower visitors. The results clearly show that five out of seven of these plant species were pollinated by ants . The role of the ants as pollinators seems to depend heavily on the r elative abundance of the ants with respect to the other species of the pollinator assemblage, ant pollination becoming evident when ants out number other floral visitors. The ant-pollination systems analysed in this study may be the result of prevailing ecological conditions more than an evolutionary result of a specialized interaction.