On the Evolutionary Developmental Biology of Speciation

The mainstream approaches to the study of speciation and clade diversification have extensively focused on genetic mechanisms and ecological contexts, while much less attention has been paid to the role of development. In this paper we provide materials to support the thesis that taking development into the picture of evolutionary processes can bring important insights on how species multiply and diversify. Evidence that developmentally entangled evolutionary factors are important in speciation comes from different lines of investigation that can be broadly grouped under three headings: evolvability, phenotypic plasticity, and phenology. Evolvability enters the scene through the complexity of the genotype-phenotype map, the developmental link between transmissible genetic information and selectable phenotypes. Phenotypic plasticity can act as a facilitator for speciation, promoting diversification at different stages of the speciation process, as well as generating novel targets and novel trade-offs for evolutionary processes. The formal inclusion of the developmental time axis in speciation models widens the scope for investigating the onset and/or reinforcement of reproductive barriers through a range of situations along an organism's life cycle. Overall, developmental processes can contribute to speciation and diversification at different stages of the speciation process, at different levels of biological organization and along the organism's whole life cycle.