The recurrent assembly of C4 photosynthesis, an evolutionary tale
Recent advances in genomics open promising opportunities to investigate adaptive trait evolution at the molecular level. However, the accuracy of comparative genomic studies strongly relies on the taxonomic coverage, which can be insufficient when based solely on a few completely sequenced genomes. In particular, when distantly-related genomes are compared, orthology of some genes can be misidentified and long branches of the phylogenetic reconstructions make inappropriate positive selection tests, as recently exemplified with investigations on the evolution of the C(4) photosynthetic pathway in grasses. Complementary studies addressing the diversification of multigene families in a broad taxonomic sample can help circumvent these issues.