Islands are frequently referred to as natural laboratories in ecology and evolutionary biology. Several key ecological-evolutionary concepts have first become evident on them, such as allopatric speciation processes and pervasive species-area relationships that form the backbone of island biogeography theory. Islands are also ideal for understanding ecological complexity because of their well-defined borders and simplified biota. Despite representing only c. 5% of the emerged land, islands hold a very rich biota, bearing more than 20% of all terrestrial plant and vertebrate species. Ten of the 35 world biodiversity hotspots are entirely or largely islands, bearing also have a high endemism level, which is an order of magnitude higher than that found on continents. Yet, island biodiversity -expressed not only by the species they host but also the myriad of interactions evolved among them- is still mostly unknown. In this talk I will show you some of the findings of our studies in different archipelagos, focusing on the role that vertebrates play in these ecosystems enhancing the success of plant reproduction.