Schiestl Florian P, Cozzolino Salvatore
Institute of Systematic Botany, University of Zürich, Zollikerstrasse 107, CH-8008 Zürich, Switzerland.
BMC Evol Biol. 2008 Jan 28;8:27. doi: 10.1186/1471-2148-8-27.
Within the astonishing diversity of orchid pollination systems, sexual deception is one of the most stunning. An example is the genus Ophrys, where plants attract male bees as pollinators by mimicking female mating signals. Unsaturated hydrocarbons (alkenes) are often the key signal for this chemical mimicry. Here we investigate the evolution of these key compounds within Orchidinae by mapping their production in flowers of selected species onto their estimated phylogeny.
We found that alkenes, at least in trace amounts, were present in 18 of 20 investigated species together representing 10 genera. Thus, the reconstruction of ancestral state for alkene-production showed that this is a primitive character state in Ophrys, and can be interpreted as a preadaptation for the evolution of sexual deception. Four of the investigated species, namely Ophrys sphegodes, Serapias lingua, S. cordigera, and Anacamptis papilionacea, that are pollinated primarily by male bees, produced significantly larger amounts and a greater number of different alkenes than the species pollinated either primarily by female bees or other insects.
We suggest that high amounts of alkenes evolved for the attraction of primarily male bees as pollinators by sensory exploitation, and discuss possible driving forces for the evolution of pollination by male bees.
在令人惊叹的兰花授粉系统多样性中，性欺骗是最令人称奇的一种。一个例子是眉兰属，该属植物通过模仿雌性交配信号来吸引雄蜂作为传粉者。不饱和烃（烯烃）通常是这种化学拟态的关键信号。在此，我们通过将选定物种花朵中这些化合物的产生情况映射到其估计的系统发育树上，来研究这些关键化合物在红门兰亚族中的进化。
我们发现，在20个被调查物种（共代表10个属）中的18个物种中至少存在痕量的烯烃。因此，烯烃产生的祖先状态重建表明，这是眉兰属中的一个原始性状状态，可被解释为对性欺骗进化的一种预适应。4个被调查物种，即欧洲眉兰、舌唇兰、心叶舌唇兰和粉蝶兰，主要由雄蜂授粉，它们产生的烯烃量显著更大，且不同烯烃的种类更多，相比之下，主要由雌蜂或其他昆虫授粉的物种则不然。
我们认为，大量烯烃的进化是为了通过感官利用来吸引主要作为传粉者的雄蜂，并讨论了雄蜂授粉进化的可能驱动力。
