Evolutionary origins and patterns of diversification in animal brood parasitism

Brood parasitism involves the exploitation of host parental care rather than the extraction of resources directly from hosts. Although often excluded, we show that brood parasitism fits within existing frameworks of parasitic strategies, and formulate defining criteria, including that the parasites be obligate and the hosts non-eusocial (thereby distinguishing them from social parasites). A systematic literature survey revealed 59 independently derived brood parasitic lineages with most origins (49) in insects, particularly among bees and wasps, and other origins in birds (7) and fish (3). Insects account for over 98% of brood parasitic species, with much of that diversity reflecting ancient (100+ million-year-old) brood parasitic lineages. Brood parasites usually, but not always, evolve from forms that show parental care. In insects, brood parasitism often first evolves through exploitation of a closely related species, following Emery’s rule, but this is less typical in birds, which w..., ,