Evolution of development in closely related species of flies and worms
Key PointsThe extensive knowledge of the genetic basis for development of the model organisms Drosophila melanogaster and Caenorhabditis elegans, together with their complete genome sequences, provides a useful tool for comparing their development with that of other closely related species. To identify the genetic changes that underlie small morphological differences, recent studies have used either a candidate-gene approach or, where hybrids are viable, direct classical genetics. This approach can allow the rapid identification of genes that contribute to phenotypic change. Evolution of cis-regulatory sequences that alters gene expression might contribute to phenotypic change. Regulatory modules of developmental genes are subject to continuous sequence change and to stabilizing selection in the absence of morphological change. Co-evolution of transcription factors and their binding sequences can be readily shown using comparisons between closely related species. The redundant cellular interactions that underlie the development of a structure and that contribute to its robustness are also subject to continuous change. Studies of satellite species should help to bridge the gap between evolutionary genetics and comparative embryology.AbstractOne of the main challenges in evolutionary biology is to identify the molecular changes that underlie phenotypic differences that are of evolutionary significance. Comparative studies of early development have shown that changes in the spatio-temporal use of regulatory genes, as well as changes in the specificity of regulatory proteins, are correlated with important differences in morphology between phylogenetically distant species. However, it is not known how such changes take place in natural populations, and whether they result from a single, or many small, additive events. Extending this approach to the study of development of closely related species promises to enrich this debate.