No interactions present.
... bears flowers single or in pairs in the leaf axils.
This might be Vaccinium vitis-idaea.
V. vitis-idaea then is a better option...
V. vitis-idaea shows distinct 'holes' or 'dots' on the leaves (they may be stomata - I can't recall). I could not see these on these images and hence my suggestion of genus rather than species. I know little of the Ericacae in Spain...it may be another genus such as Arctostaphyllos....I am fairly certain it is not V. v-i.
... and it seems that the only two possibilities are Vaccinium vitis-idaea and Arctostaphyllos uva-ursi. (Not Arbutus (unless I have the scale really wrong), Calluna, Daboecia, Erica, Loiseleuria, Phyllodoce or Rhododendron; only one evergreen species in each of Arctostaphyllos and Vaccinium.
Fide Stace, Vaccinium has an inferior ovary, Arctostaphyllos a superior one.
Looking at the photographs this has a superior ovary.
The flower at the top right has been attacked by a bee (probably) involved in nectar theft. It pierces the flower to get at the nectar without picking up pollen. On some days on the Quantocks you can hear the bees attcking Bell heather
Thank you very much for all explainations.
This was not an arbust
Further more, the description of Arctostaphyllos uva-ursi's leaves fits better as the edges of V.vitis-idaea are round (not the case here)
Lat/Lng: 42.6, -2.76