Coexistence of Ambrosia chamissonis and Ammophila arenaria in coastal dunes in the Ñuble Region, Chile

•Plant distribution in dunes could be determined by soil salinity and phosphorus.•Plant performance may be influenced by the interactions they establish.•Ambrosia chamissonis is a competitive species in the extreme of the stress gradient.•Ammophila arenaria depend on facilitation to inhabit highly stressful areas.•Coastal dune plants do not always follow the stress gradient hypothesis.