Fermentative Yeast Diversity at the Northern Range Limit of Their Oak Tree Hosts

Fermentative yeasts play important roles in both ecological and industrial processes, but their distribution and abundance in natural environments are not well understood. We investigated the diversity of yeasts at the northern range limit of their oak tree hosts (Quercus spp.) in Sweden, and identified climatic and ecological conditions governing their distribution. Yeasts were isolated from bark samples from 28 forests and identified to the species level using DNA metabarcoding. Most communities were dominated by species in the Saccharomycetaceae family, especially by species of Saccharomyces, Kluyveromyces and Pichia. Each genus showed a distinct latitudinal and longitudinal distribution, and both temperature and precipitation metrics predicted significant variation in their abundance. Consistent with this, laboratory assays revealed significant effects of temperature on the growth of strains collected from different longitudes and latitudes. We found that older trees harbour more diverse and more balanced fermentative yeast communities with more evenly distributed species abundances. Communities across trees were more similar when sharing a common dominant species. This work provides a baseline for future studies on the impact of climate change on the fermentative yeast biodiversity of temperate forests in northern latitudes and contributes to a growing collection of wild isolates for potential biotechnological applications.

发酵酵母在生态与工业进程中均发挥关键作用，但目前学界对其在自然环境中的分布与丰度仍缺乏充分认知。本研究以瑞典境内栎属（Quercus spp.）宿主的北部分布极限区域为研究对象，对酵母多样性展开调查，并明确了调控其分布的气候与生态条件。研究人员从28处森林的树皮样本中分离酵母，并通过DNA宏条形码（DNA metabarcoding）技术完成物种水平鉴定。多数酵母群落以酵母菌科（Saccharomycetaceae）物种为优势类群，尤以酿酒酵母属（Saccharomyces）、克鲁维酵母属（Kluyveromyces）与毕赤酵母属（Pichia）物种最为常见。各属酵母均呈现出独特的纬度与经度分布格局，温度与降水相关指标均可显著预测其丰度变化。与此一致的是，实验室培养实验证实，温度对采自不同经纬度的酵母菌株生长具有显著影响。研究发现，树龄更长的栎树所承载的发酵酵母群落多样性更高、结构更均衡，物种丰度分布也更为均匀。若不同树木的酵母群落拥有共同的优势物种，则群落组成的相似性更高。本研究为未来探讨气候变化对北温带森林发酵酵母生物多样性的影响提供了基准数据，同时也为潜在生物技术应用的野生酵母菌株库增添了新的样本资源。