When I was looking into Martin's 00-15e Retro, I came across a bit of information from One Man's Guitar online review. He stated that since 2014 Martin has been using Sipo an African Mahogany in their 15M series guitars.
http://onemanz.com/guitar/reviews/ac.../00-15e-retro/
South American Mahogany is becoming scarce, Sipo is of the same botanical family as the South American Mahogany. The review says that Martin's Wood Buyer has said that of all of the cousins of Mahogany, Sipo has the most similar tonal qualities to South American. The discontinued 00-15e Retro is by the way a very nice guitar.