The distinct vertebral band of black blotches gives it away as a Podarcis siculus of the northern type. I checked and found that there has been even an endemic subspecies described for these islands - Podarcis siculus sanctinicolai. 

Thanks Jeroen for the ID.
Is the sanctinicolai subspecies the only one present on the Tremiti islands? Is there a criteria (visible on photographs) that one can use to identify this subspecies?
 

As a rule, no Podarcis subspecies coexist on a single European island of such small size. I have absolutely no idea about the distincive features of this particular subspecies, but the male in the picture on this page has quite remarkable green lines, different from any siculus I have ever seen =>

http://www.lacerta.de/AS/Bildarchiv.php?Subspecies=190&Kind=1&RegioId=310&Regio=Insel Tremiti&PHPSESSID=urq2mo0pfotd876veflbmto5g2

Note that this is a species with extreme high variability in its pattern, differing between but also significantly within populations. It is likely that a lot of the subspecies of this species should be omitted, due to lack of any phylogenetic, but also consistent morphological substantiation. I checked some papers, and it seems that this population has not yet been sampled for molecular analysis (DNA).