Flower clades and fruit clades: Trade-offs in color diversification across angiosperms

Flowers and fruits are two major phases of plant reproduction that often use colorful signals to attract animal mutualists. Fruits develop from the ovaries of flowers, and both organs use the same suites of pigments to create color. These developmental links and functional similarities led us to test for correlations in flower and fruit color lability across clades.

We selected 51 clades (2960 species) of animal-pollinated and animal-dispersed (i.e., fleshy-fruited) plants and scored flower and fruit color into eight discrete (human-perceived) categories for the same set of species in each clade. We used stochastic character mapping to estimate the number and rates of transitions among colors in flowers and fruits.

The number of transitions in flower and fruit color was negatively correlated across clades (R² = 0.41; P < 0.001). Among animal-pollinated and animal-dispersed clades, 67% were "fruit clades" biased toward fruit color lability, while 29% were "flower clades" biased toward flower color lability. Furthermore, clades with yellow- or orange-flowered species also tended to have those colors in their fruits, and red flowers were more common in "flower clades" and brown fruits in "fruit clades".

These patterns suggest that clades specialize on one phase of reproduction or the other. Possible explanations include constraints on energetic investment into either pollination or dispersal, environmental factors that select for color diversification in one organ but not the other, or constraints imposed by the underlying structure of pigment pathways.