Correlations between pigment categories
To test whether pteridines replace carotenoids with a similar hue
(carotenoid-mimicry hypothesis; Grether et al. 1999), we examined
the relationships between either red ketocarotenoids and drosopterin, or
yellow-orange dietary carotenoids and xanthopterin. Neither relationship
was significant (Figure 3), although there were significant associations
between other pigment categories. Specifically, there was a significant
positive correlation between the concentration of dietary carotenoids
and ketocarotenoids, and between other pteridines and xanthopterin, and
a negative correlation between xanthopterin and ketocarotenoids (Figure
3).