Nestling polymorphism in a cuckoo-host system

• Published in: Current biology Vol. 25; no. 24; pp. R1164 - R1165
• Main Authors: Sato, Nozomu J., Tanaka, Keita D., Okahisa, Yuji, Yamamichi, Masato, Kuehn, Ralph, Gula, Roman, Ueda, Keisuke, Theuerkauf, Jörn
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 21.12.2015
• Subjects: Adaptation, Biological; Animals; Birds - genetics; Nesting Behavior; Polymorphism, Genetic; Skin Pigmentation - genetics
• ISSN: 0960-9822; 1879-0445
• DOI: 10.1016/j.cub.2015.11.028

Virulence of avian brood parasites can trigger a coevolutionary arms race, which favours rejection of parasitic eggs or chicks by host parents, and in turn leads to mimicry in parasite eggs or chicks [1–7]. The appearance of host offspring is critical to enable host parents to detect parasites. Thus, increasing accuracy of parasites’ mimicry can favour a newly emerged host morph to escape parasites’ mimicry. If parasites catch up with the hosts with a newly acquired mimetic morph, host polymorphism should be maintained through apostatic (negative frequency-dependent) selection, which favours hosts rarer morphs [1–3,7]. Among population-wide polymorphism, uniformity of respective host morphs in single host nests stochastically prevents parasites from targeting any specific morph of hosts and thus helps parents detect parasitism. Polymorphism in such a state is well-known in egg appearances of hosts of brood parasitic birds [2,3,7], which might also occur in chick appearances when arms races escalate. Here, we present evidence of polymorphism in chick skin coloration in a cuckoo–host system: the fan-tailed gerygone Gerygone flavolateralis and its specialist brood parasite, the shining bronze-cuckoo Chalcites lucidus in New Caledonia (Figure 1A–C). Sato and colleagues document a case of cuckoo chicks displaying the same color polymorphism as their host bird chicks.