How do acacias match with native pollinators in invaded areas? Differences and similarities among Italy, Croatia and Portugal.

Australian acacias are popularly known as plants showing beautiful flowers, but they have also been introduced to Europe for reforestation purposes in areas suffering frequent fires or in sand dunes. Unfortunately they turned out to be aggressive invaders and are today the subject of different lines of research. One involve their reproduction: Acacias are full or partial selfincompatible, the result of self-pollination often showing deleterious recessive genes in the population and a decrease in fertility and in general vigour. Cross-pollination is the rule: at their home range, cross-pollination is ascribed to the activity of birds, attracted by extrafloral nectar, and, to a smaller extent, to rare bee visits to inflorescences. A project, involving different research groups, started back in 2012 to address the above question and deepen the understanding of how these species establish a functional relationship with the pollinators needed for their successful reproduction. Data have been collected in three countries so far, on different species: Acacia dealbata, A. pycnantha, and A. longifolia. Field observations have been conducted to identify potential pollinators and their activity on flowers. Results indicate that the honeybee is the main pollinator attracted by these species, and that in certain circumstances it already developed a precise strategy to exploit all the resources offered by the alien plant. A special role is played by extrafloral nectaries (EFN), usually known as related to mutualisms with ants. EFN evolution and role need to be discussed further. Understanding plant-pollinator interactions is crucial when addressed to alien invasive species: indeed, the presence of attractive exotic plants may turn the interest of pollinators away from native plants. Moreover, we have to take into account actual pollinator decline, climate change scenarios and influence and pressure of economic processes.