San Francisco State University, 1600 Holloway Avenue, San Francisco, California 94132 USA.
Am J Bot. 2008 Dec;95(12):1652-9. doi: 10.3732/ajb.0800118.
Floral reproductive morphology and scent are of primary importance to pollinators in guiding foraging decisions. We compared the floral scent and reproductive morphology between two subspecies of Linanthus dichotomus (Polemoniaceae) that are taxonomically distinguished by geography and flowering time: the vespertine L. dichotomus subsp. dichotomus and the diurnal L. dichotomus subsp. meridianus. Disparity in flowering time between the two subspecies is accompanied by differences in flower visitors. We collected floral volatiles using dynamic headspace methods and analyzed them using gas chromatography and mass spectroscopy. Together, the subspecies produced a total of 39 floral scent compounds. Subspecies differ in the quantitative pattern of volatiles that attract noctuid moths (e.g., lilac aldehydes) vs. a more general suite of visitors (e.g., phenylacetaldehyde), but not in overall scent emission rates. A discriminant function analysis correctly distinguished between the two subspecies based on scent samples 86% of the time. We measured seven reproductive morphological traits; a discriminant function analysis distinguished between the two subspecies based on morphological samples 81% of the time. We found significant differences between subspecies in scent but not in individual morphological traits. The evidence presented here is most consistent with a hypothesis of pollinator-mediated selection.
花部繁殖形态和气味对传粉者在觅食决策中具有重要意义。我们比较了两种地理和开花时间上有区别的二色补血草（蓝雪科）亚种的花部气味和繁殖形态：黄昏型二色补血草亚种和昼型二色补血草亚种。两个亚种之间开花时间的差异伴随着花访客的差异。我们使用动态顶空方法收集花朵挥发物，并使用气相色谱和质谱法对其进行分析。这两个亚种共产生了 39 种花部气味化合物。亚种在吸引夜蛾（如紫丁香醛）和更广泛的访客（如苯乙醛）的挥发性物质的定量模式上存在差异，但在整体气味排放率上没有差异。判别函数分析基于气味样本 86%的时间正确区分了两个亚种。我们测量了七个繁殖形态特征；判别函数分析基于形态样本 81%的时间区分了两个亚种。我们发现气味在亚种间存在显著差异，但个体形态特征没有差异。这里提出的证据最符合传粉媒介选择的假说。
