Evolution of pollinator specialization and de-specialization in Echinopsis (Cactaceae, Trichocereeae)

当植物物种分散到新的栖息地，他们往往会遇到一个新的传粉动物区系，并经历不同的传粉者选择制度造成的花形态的变化。这被认为有助于物种的形成，当不同的形式后来进入第二次接触，但不再能产生合适的后代。拟议的研究将研究仙人掌科的六个小分支的授粉，每个分支有3-5个非常密切相关的物种（不同的种群），以研究哪些形态和生理花性状与蜜蜂，蜂鸟和天蛾授粉之间的变化相关。焦点分支，这属于大属松果菊（Trichocereeae），被选中，因为初步数据表明，传粉者在物种分化和生殖隔离中发挥作用，也有明显的双峰授粉策略的情况下。我们假设，从天蛾到蜜蜂授粉的转变相对容易，而从蜜蜂到鸟类或天蛾授粉的转变则比较困难。除了实际的奖励（花蜜和/或花粉）之外，所有三种授粉综合征都涉及许多性状，本项目将重点关注与传粉者变化的六个可能方向相关的花香变化。通过集中在几个小的分支，我们将能够结合联合收割机在几个地点的实地观察与物种/种群水平的系统发育分析和花的气味的生化分析。总之，这些组成部分将允许评估更多衍生（年轻）物种是否倾向于依赖较少的传粉者，从而更加专业化，或者相反，它们是否依赖于更多种类的传粉者，从而保持或成为非专业化。这将是解决这个问题的第二项研究，也是第一项评估气味花束在扩大或缩小传粉者光谱中的作用的研究。

When plant species disperse to new habitats, they often encounter a new pollinator fauna and undergo changes in floral morphology resulting from divergent pollinator selection regimes. This is thought to contribute to species formation when the divergent forms later come into secondary contact but can no longer produce fit offspring. The proposed research will examine pollination in six small clades of Cactaceae, each with 3-5 very closely related species (divergent sets of populations), in order to examine which morphological and physiological flower traits correlate with shifts between bee, hummingbird, and hawkmoth pollination. The focal clades, which belong to the large genus Echinopsis (Trichocereeae), were selected because preliminary data suggest that pollinators play a role in species divergence and reproductive isolation; there are also cases of apparent bimodal pollination strategies. We hypothesize that shifts from hawkmoth to bee pollination are relatively easy while shifts from bee to bird or hawkmoth pollination are more difficult. All three pollination syndromes involve numerous traits besides the actual rewards (nectar and/or pollen), and this project will focus on changes in floral scents that correlate with the six possible directions of pollinator change. By focusing on several small clades we will be able to combine field observations at several sites with species/population-level phylogenetic analyses and biochemical analyses of floral odor. Together, these components will allow to assess whether more derived (younger) species tend to rely on fewer pollinators and thus are more specialized or whether on the contrary they rely on more kinds of pollinators and thus stay, or become, unspecialized. This will be only the second study to address this question and the first to assess the role of odor bouquets in the broadening or narrowing of pollinator spectra.