Before revision:  Our scheme retains the underlying methods' FDR guarantees in theory and can decrease FDR and increase power in practice .
After revision:  Our scheme retains the underlying methods' FDR guarantees in theory and simulations, and we show that it can lead to new discoveries on microbiome data from the American Gut Project. In particular, our results indicate that several phyla that have been overlooked so far are associated with obesity .