Department of Animal Ecology, Evolution and Biodiversity, Ruhr-Universität Bochum, 44801 Bochum, Germany.
J Exp Biol. 2024 Mar 15;227(6). doi: 10.1242/jeb.246995. Epub 2024 Mar 21.
Male neotropical orchid bees concoct complex perfume blends by collecting exogenous volatiles from various sources, including orchids. These perfumes, stored in specialized hind-leg pouches and released during courtship, serve as inter-sexual signals. It has been hypothesized that male perfumes honestly indicate aspects of male fitness. If perfume traits such as quantity or complexity increase over individual lifetime, perfumes could reflect age (survival) and cumulative foraging success of males. We conducted a two-season mark-recapture study with Euglossa imperialis in Costa Rica, monitoring the balance of perfume uptake and expenditure over individual male lifetime. We sealed one hind-leg pouch upon initial capture, 'freezing' the perfume status on one side, and compared it with the other side at recapture to assess changes in perfume traits over time. Additionally, we used a novel method to estimate individual age by combining two parameters of wing degradation. Contrary to predictions, young to intermediate-aged bees had the highest quantities of perfume and the highest diversity of detected compounds. At the same time, the change in perfume between recaptures was positive (increase in amount and complexity) in young bees, whereas it was neutral to negative in older bees. Although these findings do not disprove an indicator function of male perfume, they shift the emphasis to non-cumulative fitness components such as sensory acuteness or cognitive capacity as likely targets of selection. Females preferring strong perfume signals in mates would maximize speed of foraging in offspring rather than their lifetime cumulative yield.
雄性新热带兰花蜂通过从各种来源（包括兰花）收集外源性挥发物来调配复杂的香水混合物。这些香水储存在专门的后腿袋中，并在求偶时释放，作为两性之间的信号。有人假设，雄性香水确实能反映出雄性的健康状况。如果香水的特征（如数量或复杂性）随着个体寿命的增长而增加，那么香水就可以反映出雄性的年龄（生存）和累积觅食的成功。我们在哥斯达黎加对 Euglossa imperialis 进行了为期两个季节的标记-重捕研究，监测了个体雄性一生的香水吸收和支出的平衡。我们在初次捕获时封闭了一条后腿袋，“冻结”了一侧的香水状态，并在重捕时与另一侧进行比较，以评估随着时间的推移香水特征的变化。此外，我们使用一种新方法通过结合翅膀降解的两个参数来估计个体年龄。与预测相反，年轻到中年的蜜蜂拥有最多的香水数量和最多种类的检测化合物。同时，在年轻的蜜蜂中，香水在重捕之间的变化是积极的（数量和复杂性增加），而在年老的蜜蜂中则是中性到消极的。尽管这些发现并没有否定雄性香水的指示功能，但它们将重点转移到非累积的健康成分上，例如感官敏锐度或认知能力，这些可能是选择的目标。喜欢配偶中强烈香水信号的雌性会最大限度地提高后代的觅食速度，而不是它们一生的累积产量。
