The couple announced their intention to divorce in a statement to People magazine on Friday. Apparently they'd already been living separately for six months because of different work obligations.
"They will continue to share their love of music, and are still working on their debut album, 'I'm Not Falling,' releasing in 2014," the statement said. "They remain best friends and look forward to their continued journey together."
McDonald, who was on "Idol" in 2011 and known for his wild floral suits, cowboy boots and scratchy voice, was dating Reed when he was voted off the show that April. They moved in together the next month.
They'd met at the premiere of "Red Riding Hood" that March.
"She's super-cool, man, she's super-smart, really cool girl," he said of Reed at the time. "I'm happy about it. We've been hanging out, here and there, you know we're both pretty busy, but it's been fun so far."
The couple were engaged that June and married the following October, but it appears McDonald's comments about them both being busy actually presaged the end of their whirlwind romance.
Reed, who has three films coming out this year, was spotted out in L.A. over the weekend without her wedding ring.