Parental care at the molecular level: the metabolic division of labour between parents and offspring

Eleanor Kate Bladon, Sanja Hakala, Rebecca M Kilner , Adria LeBoeuf

Parental care during offspring development has traditionally been viewed as a balance between cooperation and conflict. Offspring are imagined to be too helpless to find resources, or build protection, or generate warmth themselves. According to this view, the only work carried out by the offspring is through diverse acts of supplication for these vital resources. These are the traits, therefore, that have become the focus for analysing conflict with parents. Recent work analysing parental care at the molecular and metabolic level reveals that offspring have more agency than previously supposed and therefore that development should be seen as more of a shared endeavour. It involves a dynamic metabolic division of labour between parents and offspring, from before conception to independence, which can be precisely characterised at the molecular level. We propose a framework that classifies parental care at the molecular level into three broad areas: (1) resource transfer, (2) environmental buffering and protection, and (3) information transfer. This metabolic division of labour framework provides a common currency for understanding when cooperation tips into conflict (and vice versa) by quantifying the precise costs and benefits of specific molecular transfers. The molecular approach generates insights into the evolution of the genetic pathways that underpin parental care and how parent-offspring conflicts are resolved at the biochemical level. It allows the blending of traditional theoretical approaches for analysing care with state-of-the-art comparative methods, based on -omics technologies. It therefore offers fresh insights into how adaptive parental care functions, why it persists, how it evolves and how it continues to contribute to evolution.