Data from: Predictive links between petal color and pigment quantities in natural Penstemon hybrids

Flowers have evolved remarkable diversity in petal color, in large part
due to pollinator-mediated selection. This diversity arises from
specialized metabolic pathways that generate conspicuous pigments. Despite
the clear link between flower color and floral pigment production, studies
determining predictive relationships between pigmentation and petal color
are currently lacking. In this study, we analyze a dataset consisting of
hundreds of natural Penstemon hybrids that exhibit variation in flower
color, including blue, purple, pink, and red. For each individual hybrid,
we measured anthocyanin pigment content and petal spectral reflectance. We
found that floral pigment quantities are correlated with hue, chroma, and
brightness as calculated from petal spectral reflectance data: hue is
related to the relative amounts of delphinidin vs. pelargonidin
pigmentation, whereas brightness and chroma are correlated with the total
anthocyanin pigmentation. We used a partial least squares regression
approach to identify predictive relationships between pigment production
and petal reflectance. We find that pigment quantity data provide robust
predictions of petal reflectance, confirming a pervasive assumption that
differences in pigmentation should predictably influence flower color.
Moreover, we find that reflectance data enables accurate inferences of
pigment quantities, where the full reflectance spectra provide much more
accurate inference of pigment quantities than spectral attributes
(brightness, chroma, and hue). Our predictive framework provides readily
interpretable model coefficients relating spectral attributes of petal
reflectance to underlying pigment quantities. These relationships
represent key links between genetic changes affecting anthocyanin
production and ecological functions of petal coloration.