School of Forest Resources and Conservation, University of Florida, Gainesville, FL, 32603, USA.
United States Forest Service, Northern Research Station, Center for Forest Mycology Research, One Gifford Pinchot Drive, Madison, WI, 53726, USA.
Microb Ecol. 2018 Oct;76(3):839-850. doi: 10.1007/s00248-018-1154-8. Epub 2018 Feb 24.
Separating symbioses from incidental associations is a major obstacle in symbiosis research. In this survey of fungi associated with Asian bark and ambrosia beetles, we used quantitative culture and DNA barcode identification to characterize fungal communities associated with co-infesting beetle species in pines (Pinus) of China and Vietnam. To quantitatively discern likely symbioses from coincidental associations, we used multivariate analysis and multilevel pattern analysis (a type of indicator species analysis). Nearly half of the variation in fungal community composition in beetle galleries and on beetle bodies was explained by beetle species. We inferred a spectrum of ecological strategies among beetle-associated fungi: from generalist multispecies associates to highly specialized single-host symbionts that were consistently dominant within the mycangia of their hosts. Statistically significant fungal associates of ambrosia beetles were typically only found with one beetle species. In contrast, bark beetle-associated fungi were often associated with multiple beetle species. Ambrosia beetles and their galleries were frequently colonized by low-prevalence ambrosia fungi, suggesting that facultative ambrosial associations are commonplace, and ecological mechanisms such as specialization and competition may be important in these dynamic associations. The approach used here could effectively delimit symbiotic interactions in any system where symbioses are obscured by frequent incidental associations. It has multiple advantages including (1) powerful statistical tests for non-random associations among potential symbionts, (2) simultaneous evaluation of multiple co-occurring host and symbiont associations, and (3) identifying symbionts that are significantly associated with multiple host species.
从偶然关联中分离共生关系是共生研究中的一个主要障碍。在这项对与亚洲树皮和天牛共生的真菌的调查中，我们使用定量培养和 DNA 条码鉴定来描述与中国和越南松树（Pinus）中共同侵害的甲虫物种相关的真菌群落。为了从偶然关联中定量区分可能的共生关系，我们使用了多元分析和多层次模式分析（一种指示物种分析）。甲虫洞穴和甲虫体上真菌群落组成的近一半变化可由甲虫物种来解释。我们推断出与甲虫相关的真菌具有一系列生态策略：从多物种的一般共生体到高度专业化的单宿主共生体，这些共生体在其宿主的菌囊中始终占主导地位。与天牛共生的真菌具有统计学意义的通常只与一种天牛物种有关。相比之下，树皮甲虫相关的真菌通常与多种甲虫物种有关。天牛及其洞穴经常被低流行度的天牛真菌定殖，这表明兼性天牛共生关系很常见，专业化和竞争等生态机制可能在这些动态共生关系中很重要。这里使用的方法可以有效地确定任何共生关系因频繁偶然关联而被掩盖的共生关系。它具有多个优点，包括（1）对潜在共生体之间非随机关联的强大统计检验，（2）同时评估多个共存的宿主和共生体关联，以及（3）识别与多种宿主物种显著相关的共生体。
