花蜜微生物对花蜜物化特征、传粉者行为及植物适合度的影响

Microorganisms (yeasts and bacteria) were found to dwell in floral nectar of most flowering plants. Their presence and metabolic activity in nectar may cause the change of nectar physico-chemical characteristics as well as induce direct or indirect effects on pollinator behavior and plant reproductive fitness. However, it is unclear about the diversity, spatio-temporal patterns of nectar-dwelling microorganisms as well as the interaction mechanisms among plants, nectar-dwelling microorganisms and pollinators. This study will select suitable plant materials and investigate the following three questions via field surveys and artificial control experiments: 1) Investigating the diversity and spatio-temporal patterns of nectar-dwelling microorganisms to understand the natural distribution patterns of nectar-dwelling microorganisms. 2) Testing the effect of nectar-microorganisms on nectar physico-chemical characteristics to clear what characteristics of nectar could be affected by nectar-dwelling microorganisms and the affecting mechanisms. 3) Investigating the effect of nectar-dwelling microorganisms on pollinator behavior and plant reproductive fitness to explore the recognition mechanisms of pollinators to nectar-dwelling microorganisms as well as the mechanisms through which nectar-dwelling microorganisms directly or indirectly affect plant male and female fitness. Based on the results of the above three aspects, this study will provide primary investigations of interactions among plants, nectar-dwelling microorganisms, and pollinating insects as well as a study foundation for the ecological significance of nectar-dwelling microorganisms.

微生物（酵母菌和细菌）在多数植物的花蜜中普遍存在，它们的存在及代谢活动可能改变花蜜物化特征，也可能直接或间接影响传粉者行为及植物繁殖适合度。但对于花蜜微生物的多样性，时空分布模式及植物-花蜜微生物-传粉者之间的互做机制缺乏同一性的认识。本研究拟选择合适的实验材料，通过野外实验和人工控制实验重点探讨以下3个方面的问题：1）花蜜微生物多样性及丰度的时空分布模式，借此了解花蜜微生物的自然分布式样；2）花蜜微生物对花蜜物化特征的影响，借此弄清花蜜微生物能够改变花蜜的哪些特征以及其影响花蜜物化特征的可能机制；3）花蜜微生物对传粉者行为及植物适合度的影响，借此探究传粉者对花蜜微生物的识别机制以及花蜜微生物直接或间接影响植物雌、雄适合度的作用机理。通过对以上3方面研究结果的整合，为探索植物-微生物-昆虫传粉者三元相互作用的机制及在生态系统中的意义打下良好基础。

花蜜微生物对传粉者及宿主植物的适合度影响已引起广泛关注，基于国内外针对此类问题的研究趋势及该项目的研究进展，项目执行期间主要进行了花蜜中微生物多样性及花蜜中微生物对传粉者行为和植物繁殖适合度的研究，重点开展了花蜜中接种微生物对熊蜂访花行为及植物雌性繁殖适合度影响的实验研究。获得的主要实验结果包括1）在多种植物中发现酵母菌的丰度存在时空差异，并发现这种差异与宿主植物花蜜中糖浓度相关。2）向花蜜中接种细菌或酵母菌实验表明，微生物能改变花蜜的酸碱度，进而影响访花者的行为。3）花蜜微生物多样性调查显示，多数植物花蜜中微生物多样性不高，基本为耐盐性酵母菌为主，一般种类少于10种。4）花蜜中如有重金属污染，则会改变花蜜物化特性，进而影响访花者行为和植物繁殖适合度。