The Ecology of Social Life: A Synthesis

All the chapters of this book highlight to some extent the importance of kinship in the evolution of social life throughout the animal kingdom. They also accentuate that variation in genetic relatedness alone is not sufficient to explain the occurrence or details in the organization of social life. A comparative summary of the ecological and demographic factors favoring social life reveals some striking patterns of correlated traits (sociality syndromes). Accordingly, three types of sociality can be distinguished: (i) Aphids, thrips, wood-dwelling termites and the naked mole rat are all groups of totipotent individuals without intensive alloparental care protected by altruistic defenders. They have a long-lasting bonanza-type resource and a safe nest that offers the opportunity of inheriting the natal breeding position. (ii) Social Hymenoptera and non-wood dwelling termites with sterile or subfertile workers are characterized by intensive, altruistic alloparental care that usually involves progressive food provisioning. (iii) Cooperatively breeding vertebrates and social Hymenoptera with totipotent workers (e.g., wasps and queenless ants) take an intermediate position between class (ii) and class (i). Helpers here can gain indirect fitness benefits through alloparental care as well as direct benefits through inheriting the breeding position or by founding an own nest.