collate_alpha is sensitive, and parallel_alpha_diversity likes to leave empty dirs
collate_alpha is sensitive, and parallel_alpha_diversity likes to leave empty dirs

EmbrietteH/American-Gut,wasade/American-Gut,JWDebelius/American-Gut,biocore/American-Gut,JWDebelius/American-Gut,wasade/American-Gut,EmbrietteH/American-Gut,biocore/American-Gut