Evolving associations: cooperation and conflict within and between species

点击翻译按钮获取中文摘要

Cooperation is a conundrum in evolutionary theory because cooperators bear costs to benefit others. This results in a social dilemma where everyone is better off cooperating but individuals are tempted to free ride to the detriment of all. Evolutionary game theory, EGT, has been instrumental for advancing the theory of intra-species interactions and for understanding cooperation, in particular. The problem of cooperation is exacerbated if individual actions bestow benefits to another species. Nevertheless, cross-species associations are ubiquitous in nature with vast implications ranging from conservation biology to agriculture and health: the survival of coral reefs hinges on associations between corals and algae, many plants rely on pollinators or on nitrogen fixing bacteria, while parasitoid associations can control pests, and human health depends on our associated microbiome. EGT is ideally suited to model the significantly more challenging and variegated inter-species interactions but received surprisingly little attention in the past. This proposal leverages our expertise in intra-species evolution to contrast, compare and explore inter-species interactions: similarities include mechanisms to reduce cheating through punishment, repeated interactions, population structures or outside options. Novel dynamical aspects arise through differences in competition, inheritance, timescales, individual size and ecology between the associated species. A rigorous mechanistic classification helps to organize and advance the theory of the seemingly endless varieties of cross-species associations in nature. Amalgamating EGT and adaptive dynamics, AD, promises novel insights into the evolution of associations. Theory helps to delineate conditions conducive to form and shape associations, such as the role of horizontal and vertical symbiont transmission to prevent cheating, tame parasites, or to promote transitions from parasitic to mutualistic and facultative to obligate associations. For the emergence of associations two particularly promising evolutionary pathways are considered: the cultivation of one species by another - what appears as mutualistic associations may, in effect, be sophisticated forms of exploitation - or, specialization and division of labour within species, which turns into a selective force that drives speciation and has the potential to introduce selection on the level of associations. In cultural settings the emergence of social stratification resembles species associations with competition predominantly within but interactions between strata. The evolution of social hierarchies, institutions and governments enables groups to function more efficiently by coordinating concerted efforts for the benefit of all. However, in many societies corruption poses a major challenge to social institutions. Theory helps to identify measures to prevent the degradation of mutualistic associations between strata into despotic extortion.