They’re such beautiful things. For a long time V. juniperinus was used for North American material, too (V. canadensis). And I don’t know what the difference is there, either. Interesting that they separate out so nicely geographically. That’s not the most common state for lichens.

To be frank, I don’t know morphological differences between Vulpicida juniperina and V. tubulosus. Unfortunately, I’ve been unable to find a good description of V. juniperina on net or in my books. What is clear from Index Fungorum and related paper of Mattsson and Lai (Ref.3) is that both names are not synonyms.
I agree with you. On Stridvall’s photos I can see only a difference in substratum. V. juniperina seems to grow on wood, while V. tubulosus apparently doesn’t. Substrate description for V. tubulosus in Ref. 1, namely: wind exposed calcareous ground, grassland and ridges in high mountains above tree-line , corresponds very well to my observation. Another difference is distribution of both species. Maps on gbif.org show V. juniperina mostly in north Europe while V.tubulosus can be found in middle and south Alps, Pyrenean, Carpathian mountains. This corresponds well to the information in Ref.1 and to the ‘List of Lichens in Slovenia’ ( http://members.chello.at/joh annes.pruegger/uni/slovenia/ , J.Pruegger) where only V. tubulosus is listed. So, I am pretty sure my determination is correct.

I can’t tell what the technical difference is between the two species based on photos at Stridvall’s gallery. Just curious. Thanks!