After reading the front page accounts in three leading newspapers of the microbe that started out as a critter in Mono Lake and then got force-fed, like a goose for its liver, on arsenic replacing phosphorous, I remain unclear as to whether we have evidence of a parallel evolutionary tree or simply a highly selected version of the same old one. The Wall Street Journal’s story seemed to me the most discriminating, fwiw, speaking as a complete non-scientist. (Link fixed, I hope, or maybe behind pay wall.)