PLANT-VERTEBRATE SEED DISPERSAL SYSTEMS IN THE MEDITERRANEAN - ECOLOGICAL, EVOLUTIONARY, AND HISTORICAL DETERMINANTS

Investigations on vertebrate seed dispersal systems in the Mediterranean show that extremely efficient plant-disperser mutualisms do not require, and thus are not evidence for, mutual evolutionary adjustments of participants, Current Mediterranean dispersal systems have apparently been shaped by means of 1, trophic and behavioral adaptations of birds morphologically preadapted to pre-existing plant resources, and 2. disperser-mediated processes of habitat-shaping occurring at an ecological time scale. These processes depend on differential recruitment of plant species as a function of disperser preferences, rather than on adjustments based on evolutionary processes. On the plant side, there is a prevalence of historical and phylogenetic effects, which reflects a series of ecological limitations inherent to the interactions between plants and dispersal agents that constrain plant adaptation to dispersers. To test adaptive hypotheses and explanations, future investigations on Mediterranean plant-disperser systems should concentrate more on the animal than on the plant side of the interaction.