不同海拔山育杜鹃"传粉生态型"形成的研究

Geographical variation in floral traits within a species adaptive to local effective pollinators has been widely observed in recent years. Such an association of geographical variation in pollinator assemblages with floral divergence is referred as “pollination ecotype”. It remains much debate on whether geographical diversification in floral traits can further promote the formation of new species. Rhododendron (Ericaceae) is a species-rich genus and strongly diverse in southwest China. Many Rhododendron species can be seen in low and high-altitude mountainous areas. The floral morphology of some species and its pollinators vary with elevation. For example, the flower morphology in Rhododendron oreotrephes greatly varies in flower size and color at different altitudes and is likely to be pollinated mainly by local insects at low altitude areas and by birds at high altitude areas. In the proposal, to explore the usefulness of the concept of pollination ecotype, whether the floral divergence at different altitudes is driven by environmental factor or local pollinator, we plan to measure its floral traits, color and odor, and detect the nectar, volume, sugar concentration (sucrose and hexose content), and secondary metabolites in different tissues as well as vegetative traits and environmental factors. Comparisons of pollination contribution of different functional pollinator groups including birds and insects and pollen transfer efficiency to translocated flowers and plant reproductive success (different types of hand-pollination treatments) in high and low altitude populations would figure out whether these floral traits are under selection mediated by local pollinators. Our proposal aims to provide additional evidence for “Pollination ecotype” hypothesis and for local biodiversity maintained by plant-pollinator interactions.

同一植物在不同地理位置表现不同的花部特征，与当地传粉者相适应的模式，称为“传粉生态型”。这种隔离分化能否进一步促使物种形成，尚存诸多争论。杜鹃花属在我国西南地区分化强烈，同一物种分布海拔跨度大，有些物种的花部特征以及传粉者随海拔表现出明显差异。例如，山育杜鹃在高海拔主要为鸟类传粉，而低海拔以蜂类为主，那么花部特征的分化是因物理环境还是传粉者不同导致的呢？本项目拟以山育杜鹃为研究对象，测量和分析不同海拔的花特征（花大小以及相关花部特征、花蜜、花颜色和气味，不同组织器官次级代谢物含量），叶特征及环境因子；比较不同传粉功能群的贡献及其对移位花序的花粉传递效率；分析不同海拔花特征和繁殖成功是否与传粉者功能群转变有关？结合野外传粉生物学观察、花序移位实验和化学生态学分析研究杜鹃花在不同海拔鸟媒、虫媒的适应特征。该项目将为阐明“传粉生态型”假说提供确切的物种内证据，为杜鹃花属的多样性形成提供资料。

为了探究传粉者转变以及环境因子的差异对杜鹃花属植物特征变异的影响，以及杜鹃花属植物是如何适应传粉者和环境的变异，本研究主要观察百里杜鹃自然保护区不同生境杜鹃花的传粉者类型，统计并测量百里杜鹃保护区不同人为干扰程度的生境中杜鹃花的数量和花部特征，测量杜鹃花的反射光谱（海洋光谱仪），构建不同生境中杜鹃花的数量网络图，测量杜鹃花的次级代谢物的类别和相对含量（UPLC-Qtof）；测量统计云南苍山和老君山自然保护不同海拔居群的环境因子（温度、相对湿度和相对光照强度）、杜鹃花的花部特征，植株数量，杜鹃花花蜜（HPLC方法）和次级代谢物的类别和相对含量。百里杜鹃自然保护区杜鹃花的主要传粉者为蜜蜂属和熊蜂属昆虫，同一种杜鹃花在不同生境中其传粉者类型没有发生转变。迷人杜鹃植株数量显著多于马缨、露珠杜鹃。高强度干扰生境中马缨杜鹃和露珠杜鹃的营养器官和繁殖器官特征显著减小，不同干扰强度生境对迷人杜鹃花部特征的影响不明显。马缨、迷人杜鹃的花色在400-500 nm，露珠杜鹃的花色在400-700 nm波长有较高的反射;在高、中强度干扰生境中迷人杜鹃与其他两种杜鹃花均分布紧密,在低强度干扰生境中马缨杜鹃和迷人杜鹃分布更紧密。在云南苍山和老君山居群，随着海拔的升高，温度、湿度和相对光照强度降低，杜鹃花的植株高度、花冠大小和花药体积显著减小，而枝条直径、雌蕊和雄蕊长度显著增大。高海拔杜鹃花的花蜜体积和糖浓度显著高于低、中海拔，花蜜中蔗糖成分也显著性增多。杜鹃属植物主要含黄酮类、甾体类、苯丙素类、萜类和生物碱类等次级代谢物，不同海拔次级代谢物的成分和含量差异不显著，花粉和花蜜中次级代谢物的种类和含量要显著低于茎、叶、花瓣。该研究表明不同生境中同一种杜鹃花的传粉者类型没有发生转变，然而随着环境的变化，杜鹃属植物的表型特征和化学性状都存在适应性变异，然而表型变异的程度远大于次级代谢物的变异，该研究对杜鹃花的种群管理和生物多样性保护提供重要的理论基础。