Diversity (number of included species) and disparity (extent of morphospace occupied) are indicators of a clade’s success. Many large genera show high diversity with low disparity; others like Euphorbia are highly diverse but also exhibit high disparity.
Minelli analyses large plant and animal clades from the point of view of evolutionary developmental biology, focusing on three main concepts. First, evolvability, in terms of genetic or developmental conditions favouring multiple parallel evolutionary transitions. Second, phenotypic plasticity, as facilitator of speciation. Third, modularity and heterochrony. His analysis suggests priorities for future research, including the possible role of saltational evolution in fostering diversity and/or disparity.