Pictures of our experimental system, the common earwig, Forficula auricularia (Forficulidae: Dermaptera). From left to right: female tending clutch in defensive posture, male displaying the typical, curved and horn-like forceps (note the much straighter shape of female forceps), female cleaning an egg, male in front view. Pictures by Joel Meunier.
Traits expressed inside families are fascinating from an evolutionary perspective. Conflicts of interests are an inherent part of family life. An individual offspring would usually gain a fitness advantage by taking more than its fair share from the parent, while parents would do better by sticking to the mathematical definition of fairness to maximize their reproductive success. This parent-offspring conflict is thought to underlie the widespread evolution of conspicuous begging by offspring. Prominent examples for such behaviour are the begging calls of nestling birds and the tantrums of primate and human infants, but - as our own research showed - insect babies can use chemical signals (pheromones) to influence the care behaviour of their parents. A family can also be viewed as a social environment consisting of genetically related, repeatedly interacting and evolutionarily inter-dependent individuals. Caring parents provide critical resources for offspring development and juvenile survival. Their investments enhance offspring fitness at a cost to their own fitness. And offspring affect their parents' behaviours by scrambling for their attention and/or signalling their needs or quality. Thus, offspring and their parents are social environmental components affecting each other's behavioural decisions and reproductive life, and exerting selection on each other. Interestingly, families often differ considerably in the duration or quantity of care providing the raw-material for ongoing reciprocal adaptation of offspring to their parents and of parents to their offspring, that is, their "co-adaptation". Co-adaptation is evolution's answer to the questions: As a parent with demanding/undemanding offspring, should I be caring or non-caring? And: Having a caring (or non-caring) parent, should I (as an offspring) demand more care still, or be happy with what I get? Selection operates on both the offspring and parental life-stage resulting in strategies individuals use as offspring and as parent that are co-adapted within a genome. Finally, it is widely accepted that families are at the origin of so-called "higher" forms of sociality including cooperative breeding systems and eusocial systems, and that traits that evolved to mediate family interactions typically preceded more specialized forms of social behaviour. Thus, in order to understand the evolutionary origin of sociality, it is critical to understand the evolutionary causes and consequences of parental care and family life.
We use the common earwig, Forficula auricularia for our experimental research. Earwigs are an excellent experimental system to study family conflicts and parent-offspring co-adaptation. Females care for offspring unparentally, provide hatched nymphs with food and protect them against natural ennemies, and our research showed that the nymphs can influence maternal behaviour and reproduction partly through chemical signals they secrete on their cuticle. Furthermore, there is substantial variation between females in how much they care for offspring, and in how they invest resources in current versus future reproduction, a key parameter determining the amount of conflict between parent and offspring, and the selection favouring parent-offspring co-adaptation. More specifically, we study how selection from mother-offspring and sibling interactions favours the co-adaptation of parent and offspring traits investigating chemical communication and behavioural interactions, and using breeding experiments and molecular genetic approaches to understand the genetic bases of these traits. Although by far the most common and well-known species, the European earwig (F. auricularia) is by no means the sole earwig species. Earwigs represent an own insect order (Dermaptera) consisting of approximatly 1800 species worldwide, with seven species found in central Europe. They are easily recognized by their conspicuous cerci ("forceps").
Our research is funded by the Swiss National Science Foundation and the Fonds zur Förderung von Lehre und Forschung.
Several Master-projects are available in our group to work experimentally on cooperation, conflict and chemical signalling in earwig Forficula auricularia families. Interested students should contact Mathias Kölliker by e-mail (mathias.koelliker@unibas.ch). More info can be downloaded here