Differential effects of offspring condition-dependent signals on maternal care regulation in the European earwig

Abstract

Parent-offspring conflict theory predicts the evolution of offspring solicitation signals that can influence the amount and/or the duration of parental investment. Short-term effects of offspring solicitation signals on parental food provisioning have been widely demonstrated, but persistent effects of offspring signals on the maintenance of parental care have been rarely studied. Also, the relation between the amount of care provided to the brood and how it is distributed among individual offspring within a brood is not well enough understood. Here, we investigated in the European earwig (Forficula auricularia) the effects of offspring condition-dependent chemical signals on the maintenance of maternal care among broods and the distribution of maternal food within broods. Mothers were isolated from their brood for 3 days and continuously exposed to chemical signals extracted from broods of experimentally manipulated nutritional state. After re-introducing mothers to their brood, a range of maternal behaviours were quantified. We found that earwig mothers groomed their offspring significantly more after exposure to chemical extract from high-food brood in comparison with mothers exposed to extract from low-food brood, which in turn displayed significantly more aggressive behaviour. Furthermore, we manipulated offspring individual nutritional condition within the brood to evaluate the effect of offspring state on the within-brood food distribution. Within broods, poorly fed individuals received significantly more food than well-fed individuals, probably due to scramble competition. These results show that earwig nymphs express multi-component conditiondependent signals and behaviours differentially affecting maternal care provisioned to the brood and the distribution of care within broods.

Negative association between parental care and sibling cooperation in earwigs: a new perspective on the early evolution of family life?

“…In this state, benefits of food sharing and/or other forms of sibling cooperation might have played an essential role in maintaining family life, while simultaneously setting the stage for the evolution of parental provisioning, for example by providing the offspring with an additional incentive to re‐aggregate after independent foraging trips which in turn could enable the parent(s) to (mass) provision their offspring more effectively. The coexistence of maternal food provisioning and sibling food transfer in earwig families suggests that sibling food transfer might currently be maintained in families of the European earwig to compensate for low levels or even the complete lack of maternal food provisioning (Mas & Kölliker, ; Meunier & Kölliker, ; Meunier et al ., ). The overall higher prevalence of sibling food transfer as compared to maternal food provisioning is in line with this scenario, as it suggests that sibling food transfer also occurred in families in which the mother did not provision (this study), or was experimentally prevented from provisioning her offspring (Falk et al ., ).…”

An offspring signal of quality affects the timing of future parental reproduction

“…Whether in earwigs the apparent seasonal variation in the effect of nymph CHC on the timing of 2nd clutch production in F. auricularia reflects variation between early and late females in their responsiveness to a fixed chemical signal of quality, seasonal variation in the signal of quality emitted by nymphs of early versus late clutches, or both will have to be investigated in the future. We previously showed that the main effects of earwig chemical signal of quality is on maternal behaviours such as provisioning [12], grooming and aggression [14], and that maternal behaviour (i.e. exposure to and interaction with nymphs) has a main delaying effect on the timing of 2nd clutches [15].…”

“…We tested the direct effect of a previously described offspring signal of quality [12] on maternal residual fecundity in the absence of expressed maternal care. Female earwigs produce one or two clutches in their lifetime [13], provide maternal care for few weeks after hatching and adjust maternal behaviour to a condition-dependent mix of cuticular hydrocarbons (CHC) produced by the nymphs on their cuticle [12,14]. This system allowed us to experimentally expose females to the isolated offspring signal in the absence of expressed maternal behaviour.…”

Pre‐ and postcopulatory sexual selection and the evolution of sexually dimorphic traits in earwigs (Dermaptera)

“…; Dobler & Kölliker ; Miller & Zink ), provisioning behavior and its regulation (Staerkle & Kölliker ; Mas et al . ; Suzuki , ; Mas & Kölliker ; Meunier & Kölliker 2012b; Wong & Kölliker ), evolution of the number of reproductive cycles (Meunier et al . ), possible viviparity in a tropical species (Kočárek ) and reproduction in poorly known primitive representative species (Matzke & Klass ; Shimizu & Machida , 2011a, b).…”