Because many plants ensure their reproductive success using some level of self-fertilization, it is predicted that the balance between pollinator-mediated pollen transfer and autonomous selfing will be correlated with habitat harshness and pollinator activity. To study these correlations, we used three annual species that differ in their self-incompatibility and compared their reproductive success in the form of fruit production and seed viability, with and without pollinators, along a rainfall gradient and in relation to pollinator activity. We found that pollinator activity decreased with increasing aridity. Although the reproductive success in the absence of pollinators fitted the species’ level of self-incompatibility, no clear trend was detected between pollinator visits or site harshness and relative reproductive success. Only one of the species, Sinapis alba, showed a consistent increase in autonomous selfing with both increased aridity and decreased pollinator visits, a finding that was supported by an increase in the viability of seeds produced in the absence of pollinators. Nevertheless, unlike our prediction, the absolute number of seeds produced per S. alba flower increased with aridity. Our overall findings suggest that despite decreasing pollinator abundance and diversity with increasing aridity, the reproductive success of annual species, even of those with high self-incompatibility, remains relatively high. Although there may be several mechanisms governing these results, the overall constant seed production despite environmental uncertainties may be part of the mechanism by which plants in arid ecosystems buffer environmental variations.

中文翻译：

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沿降雨梯度生长的一年生十字花科植物自交和传粉媒介繁殖之间平衡变化的模棱两可的证据

由于许多植物通过某种程度的自花受精来确保它们的繁殖成功，因此预计传粉媒介介导的花粉转移和自主自交之间的平衡将与栖息地的恶劣程度和传粉媒介的活动相关。为了研究这些相关性，我们使用了三个自交不亲和性不同的一年生物种，并比较了它们在果实生产和种子活力方面的繁殖成功率，有无传粉者，沿降雨梯度和与传粉者活动有关。我们发现传粉媒介活动随着干旱的增加而降低。尽管在没有传粉者的情况下繁殖成功符合物种的自交不亲和水平，但在传粉者访问或场地恶劣与相对繁殖成功之间没有发现明显的趋势。Sinapis alba显示出自主自交的持续增加，同时干旱增加和传粉者访问减少，这一发现得到了在没有传粉者的情况下产生的种子活力增加的支持。然而，与我们的预测不同的是，每株S. alba产生的种子的绝对数量花随干旱增加。我们的总体研究结果表明，尽管随着干旱的增加而减少传粉媒介的丰度和多样性，但一年生物种的繁殖成功率，即使是那些高度自交不亲和的物种，仍然相对较高。尽管可能有几种机制控制这些结果，但尽管环境不确定，但总体上持续的种子生产可能是干旱生态系统中的植物缓冲环境变化的机制的一部分。