Parental care shapes evolution of aposematism and provides lifelong protection against predators

Abstract

Social interactions within species can modulate the response to selection and determine the extent of evolutionary change. Yet relatively little work has determined whether the social environment can influence the evolution of traits that are selected by interactions with other species - a major source of natural selection. Here we show that the amount of parental care received as an offspring can influence the expression, and potential evolution, of warning displays deployed against predators in adulthood. In theory, warning displays by prey are selected by predators for uniformity and to reliably advertise the extent to which individuals are chemically defended. However, the correlated evolution of intensity of the visual display and strength of the chemical defense is only possible if there is a genetic correlation between them. Adult burying beetles Nicrophorus vespilloides bear bright orange elytral markings which advertise their chemical defenses. We experimentally manipulated the level of maternal care that individuals received when they were larvae and then measured the strength of the correlation between the component parts of the warning display when they reached adulthood. We found that under limited care individuals were smaller and produced less conspicuous warning displays. The underlying family (genetic) correlation between the visual display and the chemical defense was weaker in individuals that received little care as larvae. We conclude that parenting by burying beetles modulates the evolvability of aposematic defense, making correlated evolutionary change in signal intensity and chemical defense less likely when they restrict care to their young.\n\nSignificance StatementParental care can improve early offspring survival against predators. However, we have little knowledge of how its effects shape the evolution of predator-prey interactions later in the offsprings life. We tested this with carrion beetles who provide care for offspring and who carry warning coloration to advertise to predators that they are chemically defended. We show that more parental care resulted in larger, more brightly coloured and chemically defended adult beetles. Furthermore, when parents had provided little care for their young we found weaker genetic correlations between warning signal salience and chemical defense. Over time, this could result in untrustworthy warning signals, which could render them ineffective against predators.