My direct ancestor- James Macdonald of Iverness Scotland b. 1788 who moved to Jamaica is also EM2 and there was no break in my Y chain up to Somerled. Find it hard to accept Somerled was an R haplogroup with all the signs pointing to a mixed heritage. See below taken from another project- son of a black stranger?? Hmmmm.
Dugall was the eldest son of King Somerled of the Hebrides. He founded the clan of MacDougalls when his father was killed in battle against the King of Scots, in 1164. Somerled was of mixed Celtic-Norse royal blood. Dugall, (Dubhgall) took over the heartland what is now called Argyll. His title being, King in the South Isles, Lord of Lorn. The surname MacDougall means Son of Dougall, the gaelic words Dubhgall, means black stranger or foreigner, so "son of black stranger" is a known expression for MacDougall.
http://fmg.ac/Projects/MedLands/SCOTTISH%20NOBILITY.htm