Spiders are diverse and abundant predators on vegetation in all terrestrial ecosystems, but only a few studies have examined their role in modulating spider–herbivore interactions throughout the year. We tested the hypothesis that spiders may reduce herbivore abundance on vegetation, resulting in lower leaf area loss and increased fitness (seed set production) of plants studied. In the tropics, this relationship will continue throughout the year. Our study was conducted in a cerrado environment in Brazil, using a shrub with glandular trichomes, Chamaecrista neesiana (Leguminosae Caesalpinioideae). We recorded phenological information, as well as the herbivorous insects and spiders present, on two groups of plants: a control group in which spiders were present and an experimental group in which spiders were removed. The results indicated that spiders had a positive indirect effect on plants by reducing leaf area loss and increasing seed set production, confirming our hypothesis. The benefits were higher in the rainy season, coinciding with the peak abundance of the spider species Peucetia flava. Our results indicate that protection against herbivory by spiders in the tropical savanna is conditional on the abundance of predators over time.

中文翻译：

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蜘蛛对 Chamaecrista neesiana (Leguminosae Caesalpinioideae) 食草和种子产量的季节性变化影响

蜘蛛是所有陆地生态系统中植被上种类繁多且数量丰富的捕食者，但只有少数研究研究了它们在全年调节蜘蛛-食草动物相互作用中的作用。我们测试了以下假设：蜘蛛可能会降低植被上的食草动物丰度，从而降低叶面积损失并增加所研究植物的适应性（种子集产量）。在热带地区，这种关系将持续全年。我们的研究是在巴西的塞拉多环境中进行的，使用具有腺毛状体 Chamaecrista neesiana (Leguminosae Caesalpinioideae) 的灌木。我们记录了两组植物的物候信息以及存在的食草昆虫和蜘蛛：存在蜘蛛的对照组和去除蜘蛛的实验组。结果表明，蜘蛛通过减少叶面积损失和增加结实率对植物产生积极的间接影响，证实了我们的假设。雨季的好处更高，恰逢蜘蛛物种 Peucetia flava 的峰值丰度。我们的结果表明，热带稀树草原中蜘蛛对食草动物的保护取决于随着时间的推移捕食者的数量。