There is a species of lichen whose common name is - no joke - the Dixie Reindeer Lichen.

(Don't believe me? Here it is, courtesy of Google Books.)

First thing I thought of? Remember that Christmas special where Santa felt like no one appreciated him, so he was going to stop bringing gifts? And somehow, a couple of the elves and one of the reindeer wound up in "Southtown, U.S.A"?

Well, maybe Dixie reindeer lichen is what reindeer eat when they're down south.

Unfortunately, it's not going on my list - although its range includes my area, it's not a bark lichen, and I'm only looking at lichens that will grow on tree bark.