The Hidden Spectrum: How Nectar Robbing May Have Shaped Flower Colour Evolution
A new study in *Functional Ecology* investigates the “bee-avoidance hypothesis” in bird-pollinated *Erica* flowers from South Africa. Using visual modelling and phylogenetic comparative methods, researchers found that bird-pollinated flowers are significantly less conspicuous to honey bees than their insect-pollinated relatives, while remaining equally visible to birds. This supports the idea that flower colour may have evolved as a defence against nectar-robbing bees, which damage flowers without pollinating them. However, the study found no link between current nectar-robbing rates and flower conspicuousness, nor between conspicuousness and mechanical traits like corolla length. This suggests that while bee-driven selective pressure may have shaped this evolutionary adaptation in the past, its maintenance is now decoupled from contemporary ecological pressures.
Why it might matter to you: This research provides a nuanced case study in coevolution and the potential for evolutionary mismatch, where a trait shaped by past selective pressures persists despite a change in its original driver. For evolutionary biologists, it highlights the importance of integrating phylogenetic comparative methods with field observations to disentangle historical adaptation from current function. Understanding such decoupling is crucial for accurate models of trait evolution and for predicting how species might respond to rapid environmental change.
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