No interactions present.
How can you tell just by the flowers? Without lower stem leaves are you not just guessing? According to my sources, P. serpyllifolia is also possible in Spain.
I try not to guess...
In the book I use (+ help of French forum)I can see 11 species of Polygala. The P. Serpyllifolia according to J.A.C Hose is also called here P. Depressa is in fact present in North of Spain, but would also have no presence of group of leaves in bottom (roseta in Spanish). Both are in the same group and the difference is the ratio length/width of the leaves. In this case it is heigh = Vulgaris.
I haven't taken picture of the bottom stem, but confirm it has no "roseta"
I hope it answered to your question
... the relevant term is "rosette". (And the adjectival form for a plant with a rosette is "rosulate".)
Lat/Lng: 42.95, -3