Evolutionary Biology & Ecology, Free University of Brussels/Université Libre de Bruxelles, Av. F.D. Roosevelt 50, Brussels, Belgium.
Ann Bot. 2013 Jun;111(6):1155-65. doi: 10.1093/aob/mct081. Epub 2013 Apr 17.
'Human-red' flowers are traditionally considered to be rather unpopular with bees, yet some allogamous species in the section Oncocyclus (genus Iris, Iridaceae) have evolved specialized interactions with their pollinators, a narrow taxonomic range of male solitary bees. The dark-red, tubular flowers of these irises are nectarless but provide protective shelters (i.e. a non-nutritive form of reward) primarily to male solitary bees (Apidae, Eucerini) that pollinate the flowers while looking for a shelter. An earlier study on orchids suggested that species pollinated predominantly by male solitary bees produce significantly larger amounts and larger numbers of different n-alkenes (unsaturated cuticular hydrocarbons). Whether or not this also applies to the Oncocyclus irises and whether pollinators are attracted by specific colours or scents of these flowers is unknown.
Using Iris atropurpurea, recording of pollinator preferences for shelters with different spatial parameters was combined with analyses of floral colours (by spectrophotometry) and scents (by gas chromatography-mass spectrometry) to test the hypotheses that (a) pollinators significantly prefer floral tunnels facing the rising sun (floral heat-reward hypothesis), and that (b) flowers pollinated predominantly by male solitary bees produce significantly larger amounts and larger numbers of unsaturated cuticular hydrocarbons (n-alkenes) in their floral scent (preadaptation to sexual-deception hypothesis).
Male bees do not significantly prefer shelters facing the rising sun or with the presence of high absolute/relative amounts and numbers of n-alkenes in the floral scent.
The results suggest that the flowers of I. atropurpurea probably evolved by pollinator-mediated selection acting primarily on floral colours to mimic large achromatic ('bee-black') protective shelters used preferentially by male solitary bees, and that pollinator visits are presumably not the result of an odour-based sexual stimulation or motivated by an increased morning floral heat reward in tunnels facing the rising sun.
传统上认为“人类红”花不太受蜜蜂欢迎，但在 Oncocyclus 属（鸢尾科鸢尾属）的一些异花授粉物种中，已经进化出与传粉者（窄范围的雄性独居蜜蜂）的特殊相互作用。这些鸢尾花的深紫红色管状花没有花蜜，但主要为雄性独居蜜蜂（Apidae，Eucerini）提供保护性庇护所（即一种非营养形式的奖励），这些蜜蜂在寻找庇护所的同时为花朵授粉。早期对兰花的研究表明，主要由雄性独居蜜蜂授粉的物种会产生大量和大量不同的 n-链烯（非角质不饱和碳氢化合物）。这种情况是否也适用于 Oncocyclus 鸢尾属，以及传粉者是否会被这些花的特定颜色或气味所吸引，目前尚不清楚。
使用 Iris atropurpurea，结合对不同空间参数的庇护所的传粉者偏好的记录以及对花色（分光光度法）和花香（气相色谱-质谱联用）的分析，来检验以下两个假设：（a）传粉者明显偏爱朝向太阳升起的方向的花朵隧道（花热奖励假说），以及（b）主要由雄性独居蜜蜂授粉的花朵在其花香中产生大量和大量数量的不饱和角质碳氢化合物（n-链烯）（性欺骗的预适应假说）。
雄性蜜蜂并没有明显偏好朝向太阳升起的方向的庇护所，也没有明显偏好具有高绝对/相对数量和数量的 n-链烯的花香。
结果表明，I. atropurpurea 的花朵可能是通过传粉媒介选择进化而来的，主要作用于花色，以模仿雄性独居蜜蜂优先使用的大型无色（“蜜蜂黑”）保护性庇护所，并且传粉者的访问可能不是基于气味的性刺激的结果，也不是因为太阳升起时朝向隧道的早晨花朵热奖励增加而引起的。
