de Vega Clara, Albaladejo Rafael G, Álvarez-Pérez Sergio, Herrera Carlos M
Departamento de Biología Vegetal y Ecología, Facultad de Farmacia, Universidad de Sevilla, Calle Profesor García González n 2. 41012 Sevilla, Spain.
Department of Animal Health, Faculty of Veterinary Medicine, Complutense University of Madrid, Avenida Puerta de Hierro s/n, 28040, Madrid, Spain.
Am J Bot. 2022 Mar;109(3):393-405. doi: 10.1002/ajb2.1834. Epub 2022 Mar 22.
Yeasts are often present in floral nectar and can influence plant fitness directly (independently of pollinators) or indirectly by influencing pollinator visitation and behavior. However, few studies have assessed the effect of nectar yeasts on plant reproductive success or compared effects across different plant species, limiting our understanding of the relative impact of direct vs. indirect effects.
We inoculated the nectar of six plant species in the field with the cosmopolitan yeast Metschnikowia reukaufii to analyze the direct and indirect effects on female reproductive success over 2 years. The pollinator assemblage for each species was recorded during both flowering years.
Direct yeast effects on female fecundity were statistically nonsignificant for all plant species. There were significant indirect, pollinator-mediated effects on fruit production and seed mass for the two species pollinated almost exclusively by bumblebees or hawkmoths, with the direction of the effects differing for the quantity- and quality-related fitness components. There were no consistent effects of the yeast on maternal fecundity for any of the species with diverse pollinator assemblages.
Effects of M. reukaufii on plant reproduction ranged from negative to neutral or positive depending on the plant species. The among-species variation in the indirect effects of nectar yeasts on plant pollination could reflect variation in the pollinator community, the specific microbes colonizing the nectar, and the order of microbial infection (priority effects), determining potential species interactions. Elucidating the nature of these multitrophic plant-pollinator-microbe interactions is important to understand complex processes underlying plant pollination.
酵母通常存在于花蜜中，可直接（独立于传粉者）或通过影响传粉者的访花和行为间接影响植物适合度。然而，很少有研究评估花蜜酵母对植物繁殖成功的影响，或比较不同植物物种间的影响，这限制了我们对直接和间接影响相对作用的理解。
我们在田间用广布酵母鲁考夫梅奇酵母接种了六种植物的花蜜，以分析其在两年内对雌性繁殖成功的直接和间接影响。在两个开花年份均记录了每个物种的传粉者组合。
对于所有植物物种，酵母对雌性繁殖力的直接影响在统计学上不显著。对于几乎完全由大黄蜂或天蛾传粉的两个物种，酵母对果实产量和种子质量有显著的、传粉者介导的间接影响，且与数量和质量相关的适合度成分的影响方向不同。对于传粉者组合多样的任何物种，酵母对母体繁殖力均无一致影响。
鲁考夫梅奇酵母对植物繁殖的影响因植物物种而异，从负面到中性或正面都有。花蜜酵母对植物授粉的间接影响在物种间的差异可能反映了传粉者群落、定殖于花蜜中的特定微生物以及微生物感染顺序（优先效应）的差异，这决定了潜在的物种相互作用。阐明这些多营养级植物 - 传粉者 - 微生物相互作用的本质对于理解植物授粉背后的复杂过程很重要。
