Department of Ecology and Genetics, Evolutionary Biology Centre, Uppsala University, Norbyvägen 18D, 752 36, Uppsala, Sweden.
Department of Biology, Lund University, SE-223 62, Lund, Sweden.
New Phytol. 2019 Jun;222(4):2009-2022. doi: 10.1111/nph.15747. Epub 2019 Mar 18.
Floral scent is a crucial trait for pollinator attraction. Yet only a handful of studies have estimated selection on scent in natural populations and no study has quantified the relative importance of pollinators and other agents of selection. In the fragrant orchid Gymnadenia conopsea, we used electroantennographic data to identify floral scent compounds detected by local pollinators and quantified pollinator-mediated selection on emission rates of 10 target compounds as well as on flowering start, visual display and spur length. Nocturnal pollinators contributed more to reproductive success than diurnal pollinators, but there was significant pollinator-mediated selection on both diurnal and nocturnal scent emission. Pollinators selected for increased emission of two compounds and reduced emission of two other compounds, none of which were major constituents of the total bouquet. In three cases, pollinator-mediated selection was opposed by nonpollinator-mediated selection, leading to weaker or no detectable net selection. Our study demonstrates that minor scent compounds can be targets of selection, that pollinators do not necessarily favour stronger scent signalling, and that some scent compounds are subject to conflicting selection from pollinators and other agents of selection. Hence, including floral scent traits into selection analysis is important for understanding the mechanisms behind floral evolution.
花香是吸引传粉者的关键特征。然而，仅有少数研究估计了自然种群中对气味的选择，并且没有研究量化了传粉者和其他选择因素的相对重要性。在芳香的orchid Gymnadenia conopsea 中，我们使用触角电位数据来识别当地传粉者检测到的花香化合物，并量化了 10 种目标化合物的排放率、开花起始、视觉展示和距的传粉者介导选择，以及传粉者介导选择。夜间传粉者对繁殖成功的贡献大于白天传粉者，但白天和夜间的气味排放都受到了显著的传粉者介导选择。传粉者选择增加两种化合物的排放，减少另外两种化合物的排放，而这两种化合物都不是总花香的主要成分。在三种情况下，传粉者介导的选择与非传粉者介导的选择相反，导致较弱或无法检测到净选择。我们的研究表明，次要的气味化合物可能是选择的目标，传粉者不一定偏好更强的气味信号，并且一些气味化合物受到传粉者和其他选择因素的冲突选择。因此，将花香特征纳入选择分析对于理解花进化背后的机制很重要。
