Data from: Colour as a backup for scent in the presence of olfactory noise: testing the efficacy backup hypothesis using bumblebees (Bombus terrestris)

The majority of floral displays simultaneously broadcast signals from multiple sensory modalities, but these multimodal displays come at both a metabolic cost and an increased conspicuousness to floral antagonists. Why then do plants invest in these costly multimodal displays? The efficacy backup hypothesis suggests that individual signal components act as a backup for others in the presence of environmental variability. Here, we test the efficacy backup hypothesis by investigating the ability of bumblebees to differentiate between sets of artificial flowers in the presence of either chemical interference or high wind speeds, both of which have the potential to impede the transmission of olfactory signals. We found that both chemical interference and high wind speeds negatively affected forager learning times, but these effects were mitigated in the presence of a visual signal component. Our results suggest that visual signals can act as a backup for olfactory signals in the presence of chemical interference and high wind speeds, and support the efficacy backup hypothesis as an explanation for the evolution of multimodal floral displays.

绝大多数花卉会同时通过多感官通道传递信号，但这类多模态展示不仅需要付出代谢成本，还会提升花卉对其拮抗生物的显眼程度。那么植物为何要投入资源构建这类高代价的多模态展示呢？
功效备份假说（efficacy backup hypothesis）提出，当环境存在波动时，单一信号组分可作为其他信号组分的备份。本研究通过设置化学干扰或强风环境，检测熊蜂区分多组人工花卉的能力，以此验证功效备份假说——这两种干扰因素均可能阻碍嗅觉信号的传递。
研究结果显示，化学干扰与强风均会延长觅食蜂的学习时长，但当存在视觉信号组分时，这类负面影响会得到缓解。
本研究结果表明，在遭遇化学干扰或强风时，视觉信号可作为嗅觉信号的备份，证实功效备份假说是解释多模态花卉展示演化的合理理论依据。