Developmental Plasticity and Heterokairy

There is a resurgence of interest in using phenotypic plasticity, ‘the environmentally sensitive production of alternative phenotypes by given genotypes’, as a framework in the study of evolutionary biology. The term developmental plasticity describes a more specific strand of investigation dealing with how alterations to developmental processes and outcomes shape such environmentally induced variation. Nested within developmental plasticity is the notion of heterokairy, the potential of a single genotype to alter the timing of a developmental event (e.g. onset of a particular structure, function or components of that function), in response to an environmental signal or influence. Here we make a case for using the term heterokairy as a way of focusing on altered timing across different biological disciplines, and we suggest a road map for such an approach. Heterokairy as an interdisciplinary term could be used to (a) bring together the substantial knowledge currently available of environmentally sensitive, genetic and hormonal control of the timing of developmental transitions, (b) embed the study of altered timing of developmental events within developmental plasticity and (c) highlight the role that plasticity can play in adaptive evolution, particularly in response to global environmental change.