Evolution of cooperation based on relatedness, negotiation and trading in a cooperative cichlid fish

All major transitions in the evolution of life are characterized by the necessity of cooperation and sacrifice of constituent parts transforming into higher complexity. Conceptually, the evolution of cooperation seems to be well understood. However, critical tests of the predictions from alternative mechanisms responsible for the establishment of evolutionarily stable levels of cooperation hardly exist. For instance, the seemingly overwhelming evidence for the importance of kin selection to the evolution of altruism is almost entirely correlational. Few studies have manipulated relatedness and measured behavioural responses and corresponding fitness effects, and several have found that relatedness in fact hampers cooperative behaviour instead of promoting it, opposite to predictions from kin selection theory. The relative significance of alternative mechanisms in addition to kin selection, such as negotiation and reciprocal trading, to explain cooperation in nature is as yet unclear.

Previous work has suggested that mutual help and trading of service and commodities are important and widespread variants of cooperative interactions among animals, which can elicit high levels of evolutionary stable cooperation. A crucial parameter in reciprocal trading is the potential time delay between subsequent interactions among social partners, because this affects the perceived or true probability to receive returns for provided help.

One aim of this project will be to vary the time axis of social decisions between concurrency and delays of different magnitude to span the entire range from coaction to long-term reciprocity. Another important issue is that in nature most social interactions involve some sort of asymmetry between concerned individuals, regardless whether this is sex, age, dominance status, body condition, individual quality, need, resource holding potential, reproductive status, residual reproductive value, etc. Consequently, in virtually any social interaction the involved individuals have different abilities and expectations about potential pay-offs from the interaction. The project aims to experimentally scrutinize the significance of asymmetries for the negotiation process between social partners about their respective cooperative effort, and estimate fitness effects of experimentally controlled cooperative behaviour in natural and semi-natural settings by manipulating at the same time relatedness and the negotiation rules in the model species N. pulcher, a cooperatively breeding Lake Tanganyika cichlid.