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Fig. 2 | BMC Evolutionary Biology

Fig. 2

From: Sex-linked genomic variation and its relationship to avian plumage dichromatism and sexual selection

Fig. 2

The correlation between reflectance-based dichromatism scores and R Z:A . Three different quantitative measurements of dichromatism —(a) PCA, (b) segment classification and (c) color discriminability—were obtained from published dataset in [24]. Light and dark paired colors represent dichromatic and monochromatic species pairs (coded in the same colors as Fig. 1). If both species in a pair have quantitative measurements of dichromatism available, their species means are connected by a solid line. Two pairs show reversed level of dichromatism in one of the three indices: red-headed woodpecker has a higher segment classification than red-bellied woodpecker (b, dark blue line), and pygmy nuthatcher has a higher color discriminability than red-breasted nuthacher (c, green line). It is unknown whether these are due to possible dichromatism outside of human visual spectrum or measurement errors. Yet, the overall correlations are still significant (p values from PGLS regression are shown in lower right corner)

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