Data and code for Caves, Dixit, Colebrook-Robjent, Hamusikili, Stevens, Thorogood, and Spottiswoode: Hosts elevate either within-clutch consistency or between-clutch distinctiveness of egg phenotypes in defence against brood parasites

In host-parasite arms races, hosts can evolve signatures of identity to enhance detection of parasite mimics. In theory, signatures are most effective when within-individual variation is low (“consistency”), and between-individual variation is high (“distinctiveness”). However, empirical support for positive covariation in signature consistency and distinctiveness across species is mixed. Here we attempt to resolve this puzzle by partitioning distinctiveness according to how it is achieved: (1) greater variation within each trait, contributing to elevated “absolute distinctiveness” or (2) combining phenotypic traits in unpredictable combinations (“combinatorial distinctiveness”). We tested how consistency covaries with each type of distinctiveness by measuring variation in egg colour and pattern in two African bird families (Cisticolidae and Ploceidae) that experience mimetic brood parasitism. Contrary to predictions, parasitised species, but not unparasitised species, exhibited a negat...