探讨隐秘花朵的适应意义：以粗丝蜘蛛抱蛋和长瓣蜘蛛抱蛋为例

Adaptation and diversification of floral traits have been thought to be moulded by pollinator mediated selection. Flowers of most plant species appear on the terminal, or display in various types of inflorescences which protrude out of branches and leaves, enhancing floral attractiveness to pollinators who transfer pollen from one plant to others. Aspidistra (Asparagaceae), containing more than 160 species, is one of the largest genera in monocots. Flowers of most Aspidistra species grow on the ground and are even buried in leaf litter, inaccessible to many potential pollinators such as bees. Species in this genus with emerged or cryptic flowers provide a model system to study why flowers tend to hide themselves from the most pollinators. To understand the adaptive strategy of these cryptic flowers, in this proposal we plan to conduct a comparative studies of pollination ecology in two Aspidistra species (A. crassifila and A. longipetala) whose flowers open on the ground usually under the leaf litter, based on our previous studies in A. dolichanthera which flowers grow high above ground without leaf litter covering. We plan to examine five potential hypotheses for these cryptic flowers, i.e., pollination by small invertebrates on the ground, brood-site deception pollination, copulation-site deception pollination, brood-site pollination and predator-hunting-prey pollination, through documenting pollinator types, visit frequencies, and pollination efficiency across populations under different habitats. To understand why these Aspidistra species tend to hide their flowers, we will quantitatively measure floral signals such as floral characteristics, light reflectance spectrum and volatile compounds and pollinator attractants. Given that little is known about its pollination systems in Aspidistra, we are expecting to find new pollination systems. This project could not only help us understand the evolution of various floral traits, but also provide insights into the species diversification in Aspidistra and conservation strategies that should be taken under the present circumstances.

花部特征的适应与分化被认为是传粉者介导的选择所致。大多数植物的单花在枝顶开放或聚集成花序，突出花在枝叶之外，以吸引传粉者或方便其进入，将花粉传递出去。蜘蛛抱蛋属是单子叶植物中的一个大属，物种分化强烈，但其大多数物种在地表开花，其隐秘花朵的适应意义有待研究。在前期开展了地上开花的长药蜘蛛抱蛋传粉系统的基础上，本项目拟选择地表开花的粗丝蜘蛛抱蛋和长瓣蜘蛛抱蛋为主要研究对象，开展传粉生态学研究。定量分析两种植物不同居群的传粉者类型、访问频率及传粉效率，来验证地表开花植物的五种可能传粉系统假说:地面爬行的无脊椎动物传粉、产卵地欺骗传粉、交配场所欺骗传粉、产卵地传粉和捕食者猎食猎物传粉。通过分析花部特征、花色的反射光谱、花挥发物等花部信号与传粉者类型，探讨蜘蛛抱蛋属植物为何产生隐秘的花朵？项目不仅可加深对花部特征进化的认识，有望在蜘蛛抱蛋属发现新的传粉系统，而且为阐明该属的分化和保护奠定基础。

花部特征的适应与分化被认为是传粉者介导的选择所致。大多数植物的花明显暴露在枝叶之外，以吸引传粉者方便其进入，将花粉传递出去。蜘蛛抱蛋属物种分化强烈，但其大多数物种在地表开花，其隐秘花朵的适应意义有待研究。.本项目开展了地表开花的粗丝蜘蛛抱蛋、长瓣蜘蛛抱蛋、石山蜘蛛抱蛋及其它隐秘花朵开放类型蜘蛛抱蛋的传粉生物学研究，结果发现其繁育系统为异交传粉，自交不亲和，依靠传粉者完成授粉结实；传粉媒介为虫媒传粉物种，主要为双翅目蕈蚊和瘿蚊，传粉者以雌性产卵为目的的访花，卵孵化后幼虫以花粉为食。研究结果确定了其为产卵地传粉，而排除了其余四种传粉系统假设。.项目研究表明蜘蛛抱蛋属花瓣反射光谱在双翅目传粉者发现花朵时起到一定作用，但自然条件下，花朵常被枯枝落叶所覆盖而隐蔽，花朵更主要的是通过气味吸引机制来达到吸引传粉者定位和访花。实验发现传粉者对蜘蛛抱蛋花朵散发的气味有显著选择偏好。蜘蛛抱蛋属植物在中越边境石灰岩地区分化强烈，多样化的生境和特化的传粉者趋使该属形成了以气味吸引传粉者，花粉作为传粉者幼虫食物的看护式传粉系统。研究结果不仅加深了对隐秘花朵的特殊性和适应意义的认识，且为阐明该属的花部特征进化和多样性保护奠定基础。.项目在执行过程中还发现并发表了蜘蛛抱蛋属8个新分类群和1个中国新记录种，完成50余种蜘蛛抱蛋属物种的花粉形态电镜扫描，丰富了蜘蛛抱蛋属物种多样性资料。