Absence of anti-parasitic defenses in an Asian population of the magpie, a regular host of the great spotted cuckoo in Europe
Abstract Antagonistic coevolution such as that between obligate brood parasites and their hosts promotes the evolution of a variety of trickeries that enhance successful rearing of their offspring. They do that by using host parental care to enhance their reproductive success, which in turn selects for host nest defenses or egg rejection. Studying these adaptations and counter-adaptations in different populations helps us to understand the complexity of coevolution between hosts and parasites. Here, we tested for anti-parasite defenses in an Asian population of magpies Pica pica, which is used as a regular host by the great spotted cuckoo Clamator glandarius in Europe. Unlike most magpie populations in Europe, cuckoo parasitism and specific anti-parasite defenses are absent from this Asian population. None of the cuckoos in the Asian population of magpies were capable of exploiting the magpies. That was due to magpies being evictors smaller than cuckoos that could not successfully utilize brood reducing hosts. Thus, the absence of cuckoo parasitism may be due to the absence of non-evictor brood parasites, while the absence of defenses is likely to be explained by the absence of coevolutionary interaction with any brood parasite in both the present and the past.