How common cuckoos adapt to multiple hosts.

Like other obligate brood parasites, common cuckoos (Cuculus canorus) reproduce by depositing eggs in "host" nests, thereby exploiting the parental care of another species. After hatching, the cuckoo chick eliminates its competition by ejecting host eggs (and/or chicks) from the nest. Given these extreme costs, hosts evolved the ability to recognize and reject foreign eggs, and cuckoos evolved eggs that mimic the appearance of host eggs to better escape detection (1). This coevolutionary arms race is complicated, however, by the cuckoo's exploitation of multiple host species, which presents a puzzle: How does a single cuckoo species evolve eggs that mimic those of many different hosts? On page 527 of this issue, Merondun et al. (2) report genomic data that reveal a complex geographic mosaic of cuckoo-host coevolution, in which maternally inherited genes, autosomal (biparental) genes, and population structure all contribute to the evolution of a diversity of cuckoo egg phenotypes. [ABSTRACT FROM AUTHOR]