Brood parasite-host coevolution in America versus Europe: egg rejection in large-sized host species


Authors: Manuel SOLER


Published: Volume 63.1, June 2016. Pages 35-48.

Language: English

Keywords: brood parasitism, coevolution, Cuculus canorus, egg rejection, Molothrus and successful resistance


The hosts of brood parasites have evolved egg-discrimination ability as a defence that allows them to reject parasitic eggs laid in their nests. Twenty-five years ago, Stephen Rothstein emphasised that rejection rates differed markedly between potential host species in Europe and America. The much more complete information available today supports Rothstein’s conclusions, but also allows new ones, especially when considering host size. For instance, successful resistance, one of the three potential long-term outcomes of brood parasite–host coevolution, is considerably more frequent in small-sized European host species and in medium-sized and large-sized Nearctic host species, while this evolutionary outcome is rare among Neotropical hosts regardless of their size. These results have never before been discussed, despite the differences being spectacular: 17 out of 19 small hosts presenting successful resistance are from Europe and 16 out of 17 medium-sized and 11 out of 13 large hosts presenting successful resistance are from North America. Interestingly, many large Nearctic hosts with a rejection rate close to 100% are corvids. The high rejection capacity shown by large Nearctic potential hosts probably evolved as a response to a highly virulent extinct brood parasite, either a large extinct cowbird or an extinct cuckoo species, which went extinct after losing the arms race against its large hosts.

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