The reproductive ecology of Medicago citrina (Font Quer) Greuter (Leguminosae): a bee-pollinated plant in Mediterranean islands where bees are absent

The reproductive ecology of Medicago citrina was studied in the Columbretes archipelago (Mediterranean Sea), where bees are absent. The flowers were self-compatible, homogamous, nectar producers, depended on large floral visitors for tripping and pollination. Several characteristics of the reproductive biology of M. citrina indicate an adaptation to an isolated environment characterised by scarcity of appropriate pollinators. As a result of this scarcity, fruit and seed set under natural conditions were significantly lower compared to hand-pollination treatments. The main flower visitors were mostly flies and blowflies, with Eristalis tenax (Syrphidae) and Calliphora vicina (Calliphoridae) being the most efficient pollinators. We argue that because M. citrina faces pollen limitation in the small islets of Columbretes, it presents an interesting case study of pollination related to island endemism and diversity.