亞洲闊葉林中酵母亞門落葉酵母的時空動態與多樣性

Abstract

酵母亞門(Saccharomycotina)酵母是森林微生物群落中的重要成員，但其多樣性和生態分佈仍缺乏充分瞭解，因許多類群豐富度低且不易偵測。本研究以台灣北部福山森林動態樣區連續47週採集的落葉樣本為核心，並結合越南與沖繩北部的探索性調查，探討亞洲闊葉林中的可培養Saccharomycotina酵母。酵母分離株經乙醇–糖富集培養(ethanol–sugar enrichment)取得，並以核糖體DNA內轉錄間隔區(ITS)序列進行分子鑑定。福山樣區共獲得687株分離株，其中613株經鑑定屬於Saccharomycotina，包含56個已描述物種及多個以ITS序列界定的操作分類單元(OTUs)，顯示當地落葉環境具有高度酵母多樣性與許多潛在的新穎類群。越南與沖繩樣本亦呈現多樣的酵母組成。福山樣區內的酵母豐富度與群聚組成呈現明顯季節性動態，在溫暖潮濕時期多樣性較高，冬季則降低。溫度相關變數與此季節性模式密切相關，而細尺度空間結構對群聚組成的影響較弱。熱生長表現分析進一步支持此結果，於較溫暖時期的菌株通常具有較高的最適生長溫度，而與較低溫時期相關的菌株則具有較低的熱偏好。綜合而言，本研究顯示亞洲闊葉林落葉中蘊含豐富且尚未充分調查的可培養Saccharomycotina酵母，並支持福山森林中經富集培養回收之森林酵母受到季節性氣候篩選。

Although Saccharomycotina yeasts are widespread in forests, their diversity and ecology remain poorly characterised because many taxa occur at low abundance and are difficult to detect. We investigated culturable Saccharomycotina in Asian broadleaf forests using a 47-week leaf-litter time series at the Fushan Forest Dynamics Plot in northern Taiwan, supplemented by exploratory inventories from Vietnam and northern Okinawa. Yeasts were recovered by ethanol–sugar enrichment and identified by ITS sequencing. At Fushan, we recovered 687 isolates, including 613 Saccharomycotina strains representing 56 described species and numerous ITS-defined OTUs, revealing high local diversity and many putatively novel lineages. The Vietnam and Okinawa surveys also yielded diverse assemblages. At Fushan, yeast richness and composition varied strongly over time, with higher diversity during warm, wet periods and lower diversity in winter. Temperature-related variables were associated with these seasonal patterns, whereas fine-scale spatial structure was comparatively weak. Thermal performance assays supported this association: strains recovered during warmer periods tended to have higher thermal optima than those associated with cooler periods. Together, these results show that Asian broadleaf-forest litter harbours diverse, and incompletely sampled culturable Saccharomycotina, and support seasonal climatic filtering of enrichment-recovered forest yeasts at Fushan.