Evidence for the existence and spatial distribution of a chemical variability in Helleborus multifidus vis. subsp. istriacus (Schiffner) Merxm. & Pod. in the North-Adriatic Karst region

Helleborus multifidus subsp. istriacus is an endemic Illyric Dalmatian species, that in the North-Adriatic area occurs at the border between Italy and Jugoslavia. The entity produces two bufadienolides (hellebrin and glucohellebrin) in the hypogeal organs. Three types of population are identified on the basis of their quantitative variations and their distributive ratio between roots and rhizomes. Their ranges have been estabilished on a 140 Km 2 area near Trieste (Friuli-Venezia Giulia). This distribution patterns seem to be related with a gradient in water availability. The correlation between phytochemical variability and variation of climatic factors, suggest that the investigated substances could have an adaptative value in respect with the ecology of the Helleborus entity.