Take a look at our study investigating some of the history of the Vaccinium myrtillus complex:

https://bioone.org/journals/systematic-botany/volume-45/issue-3/036364420X15935294613383/Introgression-Among-Three-Western-North-American-Bilberries-Vaccinium-Section-Myrtillus/10.1600/036364420X15935294613383.short