Hoffman Michele T, Arnold A Elizabeth
Division of Plant Pathology and Microbiology, Department of Plant Sciences, 1140 East South Campus Drive, University of Arizona, Tucson, AZ 85721, USA.
Mycol Res. 2008 Mar;112(Pt 3):331-44. doi: 10.1016/j.mycres.2007.10.014. Epub 2007 Nov 7.
Understanding how fungal endophyte communities differ in abundance, diversity, taxonomic composition, and host affinity over the geographic ranges of their hosts is key to understanding the ecology and evolutionary context of endophyte-plant associations. We examined endophytes associated with healthy photosynthetic tissues of three closely related tree species in the Cupressaceae (Coniferales): two native species within their natural ranges [Juniperus virginiana in a mesic semideciduous forest, North Carolina (NC); Cupressus arizonica, under xeric conditions, Arizona (AZ)], and a non-native species planted in each site (Platycladus orientalis). Endophytes were recovered from 229 of 960 tissue segments and represented at least 35 species of Ascomycota. Isolation frequency was more than threefold greater for plants in NC than in AZ, and was 2.5 (AZ) to four (NC) times greater for non-native Platycladus than for Cupressus or Juniperus. Analyses of ITS rDNA for 109 representative isolates showed that endophyte diversity was more than twofold greater in NC than in AZ, and that endophytes recovered in AZ were more likely to be host-generalists relative to those in NC. Different endophyte genera dominated the assemblages of each host species/locality combination, but in both localities, Platycladus harboured less diverse and more cosmopolitan endophytes than did either native host. Parsimony and Bayesian analyses for four classes of Ascomycota (Dothideomycetes, Sordariomycetes, Pezizomycetes, Eurotiomycetes) based on LSU rDNA data (ca 1.2 kb) showed that well-supported clades of endophytes frequently contained representatives of a single locality or host species, underscoring the importance of both geography and host identity in shaping a given plant's endophyte community. Together, our data show that not only do the abundance, diversity, and taxonomic composition of endophyte communities differ as a function of host identity and locality, but that host affinities of those communities are variable as well.
了解真菌内生菌群落如何在其宿主的地理范围内，在丰度、多样性、分类组成和宿主亲和力方面存在差异，是理解内生菌与植物关联的生态学和进化背景的关键。我们研究了与柏科（松柏目）三种近缘树种健康光合组织相关的内生菌：两种处于其自然分布范围内的本土物种[弗吉尼亚刺柏生长在北卡罗来纳州（NC）的湿润半落叶林中；亚利桑那柏生长在亚利桑那州（AZ）的干旱条件下]，以及在每个地点种植的一种非本土物种（侧柏）。从960个组织片段中的229个中分离出了内生菌，它们至少代表了35种子囊菌。北卡罗来纳州植物的分离频率比亚利桑那州的植物高出三倍多，非本土的侧柏的分离频率是柏木或刺柏的2.5倍（亚利桑那州）到4倍（北卡罗来纳州）。对109个代表性分离株的ITS rDNA分析表明，北卡罗来纳州内生菌的多样性比亚利桑那州高出两倍多，而且相对于北卡罗来纳州的内生菌，在亚利桑那州分离出的内生菌更有可能是宿主广适性的。不同的内生菌属在每种宿主物种/地点组合的群落中占主导地位，但在两个地点，侧柏所携带的内生菌的多样性都比任何一种本土宿主少，且更具世界性。基于LSU rDNA数据（约1.2 kb）对四类子囊菌（座囊菌纲、粪壳菌纲、盘菌纲、散囊菌纲）进行的简约分析和贝叶斯分析表明，得到充分支持的内生菌分支通常包含来自单个地点或宿主物种的代表，这突出了地理和宿主身份在塑造特定植物的内生菌群落中的重要性。总之，我们的数据表明，内生菌群落的丰度、多样性和分类组成不仅因宿主身份和地点而异，而且这些群落的宿主亲和力也是可变的。
