Figure 2. Egg phenotypes and haplotype networks.

(a) Examples illustrating host-specific egg mimicry and the tremendous variation in egg colour among common cuckoo host races. From left: meadow pipit Antus pratensis, brambling Fringilla montifringilla, great reed warbler Acrocephalus arundinaceus and common redstart Phoenicurus phoenicurus (in each clutch, the cuckoo egg is slightly larger). All photos by B.G.S. Haplotype networks for (b) COI—mitochondrial DNA, (c) CHD-W—nuclear W chromosome, (d) MYO—nuclear autosomal (2N) and (e) SPIN—nuclear Z chromosome, all sequenced in common cuckoo host races from Europe and Asia. Each coloured circle represents a unique haplotype, the relative frequency of which in our sample is proportional to area. Samples from females of different host races are colour-coded as indicated. Each line segment represents a single nucleotide difference, with small open circles indicating intermediate haplotypes not found in our sample. Sample size for the autosomal MYO gene is larger because each sample yields two alleles.