Sibling cooperation in a genus with interspecific variation in offspring dependence

Madlen Prang1, Lena Zywucki1, Maximilian Körner1, Sandra Steiger1
1 Evolutionary Animal Ecology, University of Bayreuth

O 4.11 in Methods in Ecology and Environmental Research

14.10.2021, 10:09-10:15, H 36

Parental care and family life are widespread in animals, and understanding what social processes drive the evolution of sociality is a major challenge. Behavioral biologists consider that parental care is an important driver in the evolution of sociality, and once parental care evolved, it is assumed that the traits of parents and offspring co-evolve and lead to an increase in offspring dependence on parental care. Although parental care increases the offspring’s fitness, it also leads to conflict among family members. While offspring were long thought to primarily interact competitively, recent studies revealed the potential importance of sibling cooperation. Theories suggest that the degree of cooperation in offspring interactions depends on the degree of offspring dependence on parental care: offspring unable to forage on their own should compete more, whereas more independent offspring  may increase the degree of cooperation.

In this study, we investigated this theory by using a multispecies approach. This approach allows us to compare behavioral differences within a genus in a comparable context. Here we used several burying beetle species that show dramatic variance in offspring dependence to investigate the occurrence and degree of sibling cooperation. To this end, we manipulated the brood sizes (number of siblings) and measured the effect on the offspring's growth rates.

We found that only species with more independent offspring cooperated when receiving care. Our results suggest that some forms of sibling cooperation might have already been present in an early ancestor of burying beetles. Overall, these findings give important insights into the transition from independent to dependent family life.

Keywords: parental care family life social evolution comparative approach behavioural biology evolutionary biology

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