Estación Biológica de Doñana, Consejo Superior de Investigaciones Científicas (CSIC), Avenida Américo Vespucio s/n, Isla de La Cartuja, 41092, Seville, Spain.
Microb Ecol. 2011 Jan;61(1):82-91. doi: 10.1007/s00248-010-9682-x. Epub 2010 May 8.
Floral nectar of insect-pollinated plants often contains dense yeast populations, yet little quantitative information exists on patterns and magnitude of species richness of nectar-dwelling yeasts in natural plant communities. This study evaluates yeast species richness at both the plant community and plant species levels in a montane forest area in southern Spain, and also explores possible correlations between the incidence of different yeast species in nectar and their reported tolerance to high sugar concentrations, and between yeast diversity and pollinator composition. Yeast species occurring in a total of 128 field-collected nectar samples from 24 plant species were identified by sequencing the D1/D2 domain of the large subunit rDNA, and rarefaction-based analyses were used to estimate yeast species richness at the plant community and plant species levels, using nectar drops as elemental sampling units. Individual nectar samples were generally characterized by very low species richness (1.2 yeast species/sample, on average), with the ascomycetous Metschnikowia reukaufii and Metschnikowia gruessii accounting altogether for 84.7% of the 216 isolates identified. Other yeasts recorded included species in the genera Aureobasidium, Rhodotorula, Cryptococcus, Sporobolomyces, and Lecythophora. The shapes and slopes of observed richness accumulation curves were quite similar for the nectar drop and plant species approaches, but the two approaches yielded different expected richness estimates. Expected richness was higher for plant species-based than for nectar drop-based analyses, showing that the coverage of nectar yeast species occurring in the region would be improved by sampling additional host plant species. A significant correlation was found between incidence of yeast species in nectar and their reported ability to grow in a medium containing 50% glucose. Neither diversity nor incidence of yeasts was correlated with pollinator composition across plant species.
传粉昆虫的花朵花蜜中通常含有密集的酵母种群，但关于自然植物群落中花蜜栖酵母的物种丰富度模式和幅度的定量信息很少。本研究评估了西班牙南部山区森林地区植物群落和植物物种水平上的酵母物种丰富度，还探讨了花蜜中不同酵母物种的出现与它们报道的耐高糖浓度之间的可能相关性，以及酵母多样性与传粉者组成之间的可能相关性。从 24 种植物的 128 个田间采集的花蜜样本中总共鉴定出了酵母物种，方法是对大亚基 rDNA 的 D1/D2 结构域进行测序，并用基于稀疏的分析来估计植物群落和植物物种水平上的酵母物种丰富度，以花蜜滴为基本采样单位。单个花蜜样本通常具有非常低的物种丰富度（平均每个样本 1.2 种酵母），其中子囊菌门的 Metschnikowia reukaufii 和 Metschnikowia gruessii 总共占鉴定出的 216 个分离株的 84.7%。记录的其他酵母包括 Aureobasidium、Rhodotorula、Cryptococcus、Sporobolomyces 和 Lecythophora 属中的物种。花蜜滴和植物物种方法的观察到的丰富度积累曲线的形状和斜率非常相似，但两种方法得出的预期丰富度估计值不同。基于植物物种的分析得到的预期丰富度高于基于花蜜滴的分析，表明通过采样更多的宿主植物物种，可以提高该地区花蜜酵母物种的覆盖率。在花蜜中发现的酵母物种的发生率与其报道的在含有 50%葡萄糖的培养基中生长的能力之间存在显著相关性。无论在物种之间的多样性还是酵母的发生率都与传粉者的组成无关。
