Figure 2.

W and Z chromosome copy number estimates across age groups. (a) Dot plot of the estimated copy number of W chromosome relative to the age of females in the blue-footed booby. Nestling–fledglings are in red; young adults are in green; middle-aged adults are in blue; old adults are in purple. Significant differences, linear model: lm[W.coverage ∼ age], p < 0.05, excluding outliers. (b) Box plot of the estimated copy number of W chromosome in the four different age groups of the blue-footed booby: nestlings–fledglings (0–1 year), young adults (2–7 years), middle-aged adults (8–11 years) and old adults (12–18 years). N-values are indicated in parenthesis. Significant differences, Benjamin–Hochberg corrected Mann–Whitney U test, p < 0.05. (c) Box plot of the estimated copy number of W chromosome in the two different age groups of the magnificent frigatebird: nestlings (1 month old) and adults (6–30 years). N values are indicated in parenthesis. Significant differences, Mann–Whitney U test, p < 0.05. (d) Same as in (b) but for the estimated copy number of Z chromosome. (e) Same as in (c) but for the estimated copy number of Z chromosome.