The low availability of pollinators in high-elevation ecosystems can lead to flowering plants showing different adaptive responses in order to assure their reproductive success. Shifts toward autogamy and asexual reproductive rates (the reproductive assurance hypothesis) and the compensatory measures to maintain outcrossing such as flower longevity and more prolonged pistil receptivity (the increased pollination probability hypothesis) are some of these responses. Several studies have tested both hypotheses, but investigations of plants of tropical alpine environments such as paramos that support these assumptions are still scarce. Puya nitida, an endemic Colombian plant species distributed in the paramo and subparamo in the Eastern Cordillera of Cundinamarca department, was used as a case study to test its reproductive characteristics that assure its sexual reproduction. We analysed the species’ floral morphology and development, its phenological patterns and its plant mating-system. We found that Puya nitida showed floral characteristics that promote pollination by birds, herkogamy and dichogamy, flowers and receptive stigmas with 9 and 12 days of longevity, respectively and an index of self-incompatibility that shows that it is mostly self-incompatible. We found a synchronic phenological pattern with an annual frequency and an intermediate duration with a peak in the period of lowest rainfall. Our results suggested that longer floral development, prolonged stigma receptivity, herkogamy and dichogamy and self-incompatibility might assure reproductive success, since the cross-pollination might be favoured when few pollinators are in attendance. Overall, these reproductive mechanisms add evidence to the increased pollination probability hypothesis, specifically for a plant species of a tropical high-elevation ecosystem where pollinators are scarce.

中文翻译：

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Puya nitida（凤梨科）在热带高海拔生态系统哥伦比亚 paramo 中的性繁殖策略

高海拔生态系统中传粉媒介的低可用性可能导致开花植物表现出不同的适应性反应，以确保其繁殖成功。转向自配和无性生殖率（生殖保证假说）和维持异交的补偿措施，如花寿命和更长的雌蕊接受性（增加授粉概率假说）是其中的一些反应。几项研究已经测试了这两种假设，但支持这些假设的热带高山环境植物的调查仍然很少，例如 paramos。溥仪，一种哥伦比亚特有的植物物种，分布在昆迪纳马卡省东部科迪勒拉的帕拉莫和亚帕拉莫，被用作案例研究，以测试其确保其有性繁殖的生殖特征。我们分析了该物种的花形态和发育、物候模式和植物交配系统。我们发现溥仪显示出促进鸟类授粉的花卉特征，雌雄同体和双雄授粉，花朵和接受柱头的寿命分别为 9 天和 12 天，自交不亲和指数表明它主要是自交不亲和。我们发现了具有年频率和中间持续时间的同步物候模式，在最低降雨量期间达到峰值。我们的研究结果表明，较长的花发育、较长的柱头接受性、雌雄同体和双雌性以及自交不亲和性可能会确保繁殖成功，因为当授粉者很少时可能有利于异花授粉。总体而言，这些繁殖机制为增加授粉概率假设增加了证据，特别是对于授粉媒介稀缺的热带高海拔生态系统的植物物种。