Zebrafish relatives as models for functional comparative genetics and genomics.

Closely related species, such as danionin fishes of the Danio, Danionella and Devario genera, often differ in their biology despite their shared evolutionary history, providing a platform for defining the molecular basis for the divergence of phenotypic traits. Such an approach requires the availability of large-scale genomic data, which have been provided by recent reports detailing the genomes of several danionins. Facilitated by the large number of genetic tools that are available for manipulation of the most studied member of this subgroup - the zebrafish, Danio rerio - the danionins have emerged as a useful comparative model system. Here we review their phylogeny and outline the phenotypic traits that are distinct to individual species or genera. We highlight how functional genetic tools such as interspecies hybridization, mutagenesis and transgenesis, as well as the recently reported genome assemblies, have enabled new avenues for hypothesis-driven and technology-driven exploration that collectively establish danionins as important genetic models for understanding a wide range of evolutionary innovations.