Gayral, P. et al. PLoS Genet. 9, e1003457 (2013).

To understand molecular evolution, researchers seek to analyze genomic variation, mutation rate and effective population size within a species and then compare the findings between species. These studies have required well-annotated genomes, and for metazoans they have been mainly restricted to humans and drosophilids. For a deeper understanding of evolution, genome-wide population studies from more diverse species are needed. Gayral et al. sequenced the transcriptomes of several individuals from two vertebrate species (hare and turtle) and three invertebrate species (oyster, termite and tunicate) and present a pipeline for cDNA assembly, read mapping and genotyping to perform de novo genome-wide population analysis. As predicted, they found higher genomic diversity in the invertebrates, but, surprisingly, they also saw that the ratio of nonsynonymous to synonymous mutations did not differ between the invertebrates and vertebrates, indicating that the efficiency of natural selection does not vary across the different phyla.