Substrate and spatial variables are major determinants of fungal community in karst caves in Southwest China

Aim: Previous studies primarily based on the culture method have revealed that caves host a high fungal diversity and that exogenous carbon sources influence fungal communities. Here, we assess the fungal diversity and distribution patterns in karst caves in Southwest China and reveal the major factors that shape the fungal communities. Location: Southwest China. Methods: Samples of air, rock, sediment, and water were collected from eight caves in Southwest China. Using high-throughput sequencing of the internal transcribed spacer 1 region of fungal rDNA, we examined the cave fungal communities in Southwest China and studied their correlations with potentially influential factors, such as substrate, cave, location and environmental variables. Results: Approximately 10,000 fungal operational taxonomic units (OTUs) spanning 15 phyla were obtained. The highest diversity genus was Penicillium, while Mortierella had the highest relative abundance. Compared with air and rock samples, sediment and water samples harboured higher diversity and distinct communities. Substrate and cave were revealed to be the key determinants of the fungal communities in caves. Sample location and sampling distance from the entrance had more significant impacts on rock and sediment communities than on air and water assemblages. The fungal assemblages in air and water samples from the cave and outside cave environments were similar, while those of rock and sediment samples were significantly different. Main conclusions: Our results indicate that sediment and water harboured higher fungal diversity than air and rock, and substrate and spatial variables are key determinants of fungal communities in caves.

研究目的：既往研究多基于培养法，已探明洞穴拥有极高的真菌多样性，且外源碳源会对真菌群落结构产生影响。本研究针对中国西南喀斯特洞穴开展真菌多样性与分布格局分析，并揭示塑造洞穴真菌群落的核心驱动因子。
研究区域：中国西南地区。
方法：从中国西南地区的8处洞穴中采集空气、岩石、沉积物及水体样本。采用真菌核糖体DNA（rDNA）内转录间隔区1（internal transcribed spacer 1, ITS1）的高通量测序技术，对中国西南地区洞穴的真菌群落进行分析，并探究其与底物、洞穴位点、采样位置及环境变量等潜在影响因子的相关性。
结果：共获得覆盖15个菌门的约10000个真菌操作分类单元（operational taxonomic units, OTUs）。多样性最高的真菌属为青霉菌属（Penicillium），而被孢霉属（Mortierella）的相对丰度最高。与空气及岩石样本相比，沉积物与水体样本的真菌多样性更高，且群落结构存在显著差异。底物类型与洞穴位点是塑造洞穴真菌群落的核心决定因素。采样位置及距洞穴入口的采样距离，对岩石与沉积物真菌群落的影响显著强于其对空气及水体真菌群落的影响。洞穴内外空气与水体样本的真菌群落组成相似，而岩石与沉积物样本的真菌群落则存在显著差异。
主要结论：本研究结果显示，沉积物与水体中的真菌多样性高于空气与岩石样本，且底物类型与空间变量是影响洞穴真菌群落的核心决定因素。