Geographic patterns in fruit colour diversity: do leaves constrain the colour of fleshy fruits?

Abstract

We tested for geographic patterns in fruit colour diversity. Fruit colours are thought to promote detection by seed dispersers. Because seed dispersers differ in their spectral sensitivities, we predicted that fruit colour diversity would be higher in regions with higher seed disperser diversity (i.e. the tropics). We collected reflectance data on 232 fruiting plant species and their natural backgrounds in seven localities in Europe, North and South America, and analysed fruit colour diversity according to the visual system of birds-the primary consumer types of these fruits. We found no evidence that fruit colours are either more conspicuous or more diverse in tropical areas characterised by higher seed disperser diversity. Instead, fruit colour diversity was lowest in central Brazil, suggesting that fruit colours may be more diverse in temperate regions. Although we found little evidence for geographic variation in fruit hues, the spectral properties of fruits were positively associated with the spectral properties of backgrounds. This result implies that fruit colours may be influenced by selection on the reflectance properties of leaves, thus constraining the evolution of fruit colour. Overall, the results suggest that fruit colours in the tropics are neither more diverse nor more conspicuous than temperate fruits, and that fruit colours may be influenced by correlated selection on leaf reflectance properties.

Bird fruit preferences match the frequency of fruit colours in tropical Asia

“…Fruit traits, such as size and shape, nutritional value, and conspicuousness1435424849 affect fruit-bird interactions. However, as birds are visually-guided foragers, they commonly use colour/colour contrast as important signals to find and assess fruits122250.…”

“…This traditional hypothesis has recently been strengthened by some studies indicating that fruit colour and trait diversity can be well explained by their animal consumers789, more so than by phylogenetic relationships among plants10. In addition to color, conspicuousness is also an important visual signal affecting bird food preferences, and red and black fruit are generally more conspicuous than other colours411121314.…”

The color of plant reproduction: macroecological trade-offs between biotic signaling and abiotic tolerance

“…Endler and Mielke (2005) derived a method to evaluate ecological color patterns based on compositional analyses (see also Aitchison, 2003). Following Burns et al (2009), I used a slightly modified version of their technique to quantify fruit conspicuousness, which was defined specifically as the contrast in color (i.e., reflected wavelengths as perceived by birds) between red and orange fruits and their natural backgrounds (leaves). First, the four cone output values (U, S, M, and L) were each divided by the sum of all cone outputs to obtain relative cone outputs (Goldsmith, 1990).…”

“…Because plants often utilize animals as vectors for successful pollination and seed dispersal, conspicuously colored flowers and fruits could act as mutualistic signals (see Schaefer and Ruxton, 2011). However, several decades of research have failed to provide consistent support for this as the sole explanation for flower and fruit hues (see Burns et al, 2009;Cazetta et al, 2012;Schaefer et al, 2014).…”

Fruit advertisement strategies in two Neotropical plant–seed disperser markets

“…The two areas house similar, diverse Neotropical bird communities that act as the main seed dispersers (Schaefer et al 2002 and references therein;Burns et al 2009). Bird communities include a variety of species ranging from large (e.g.…”