Data from: Pollen limitation, reproductive success and flowering frequency in single-flowered plants

1. Flowering plants exhibit striking interspecific and intraspecific variation in flower number, which strongly influences the reproductive success of animal-pollinated plants. However, the reproductive consequences of producing a single flower are poorly understood.
2. Here, we test if plants producing a single flower have a reproductive disadvantage compared to plants producing multiple flowers by combining field investigation of five deceptive orchids and a survey of published literature. Pollen limitation was estimated by comparing fruit production between hand pollination and open pollination. Flowering frequency was monitored over years to assess the potential advantage of producing a single flower. 3. Both single- and multiple-flowered species suffered strong pollen limitation. However, single-flowered species had significantly lower fruit set and produced fewer seeds per individual, though they had a significantly higher pollen removal than species with multiple flowers. A phylogenetically independent contrast (PIC) of 28 species representing four out of the five subfamilies of Orchidaceae revealed that fruit set was significantly positively associated with flower number. Both pollen removal and fruit set had a positive relationship with flower number within the multiple-flowered species. 4. Synthesis Current data and PIC support the hypothesis that producing a single flower has reproductive disadvantages. Single-flowered species may compensate for low female success through high flowering frequency over years. This study provides insight into costs and benefits of producing a single flower in deceptive orchids.

1. 显花植物在花数量上存在显著的种间与种内变异，这显著影响动物传粉植物的繁殖成功率。然而，学界对仅开单朵花的繁殖后果却鲜有深入了解。
2. 本研究结合对5种欺骗性兰科（deceptive orchids）植物的野外调查，以及已发表文献的系统调研，旨在检验仅开单朵花的植物是否相较于多花植物存在繁殖劣势。研究通过对比人工授粉与自然开放授粉的坐果情况，评估花粉限制（pollen limitation）水平，并连续多年监测开花频率，以研判单花植物可能具备的繁殖优势。
3. 单花与多花兰科物种均受到强烈的花粉限制。不过，尽管单花物种的花粉移除量显著高于多花物种，但其坐果率却显著更低，单株结种量也更少。针对兰科5个亚科中4个亚科的28个物种开展的系统发育独立对比（phylogenetically independent contrast, PIC）分析显示，坐果率与花数量呈显著正相关；在多花物种中，花粉移除量与坐果率均与花数量呈正相关关系。
4. 综合分析 当前研究数据与PIC分析结果均支持“单花繁殖存在劣势”这一假说。单花物种或可通过多年间较高的开花频率，弥补其较低的雌性繁殖成功率。本研究为阐明欺骗性兰科植物单花繁殖的成本与收益提供了重要学术视角。