Oregon grapes

I have no idea how several oregon grapes (mahonia aquifolium) plants have come to grow close to my river. They are certainly not native to Italy! As few of the shrubs grow just under the highway overpass, my theory is that some seeds must have been transported by the wind from a van carrying plants to a nursery. Or maybe a group of birds that had feasted on the grapes in a private garden then went to empty their bowels close to the river! Whichever the explanation, this sure is a beautiful shrub, with lovely early flowers that attract the bees.