Moyersoen Bernard, Weiβ Michael
School of Biological Sciences, Cruickshank Building, University of Aberdeen, Aberdeen, United Kingdom.
Department of Biology, University of Tübingen, Tübingen, Germany.
PLoS One. 2014 Jul 29;9(7):e103076. doi: 10.1371/journal.pone.0103076. eCollection 2014.
Pakaraimaea dipterocarpacea, a member of the Dipterocarpaceae endemic in the Guayana region, is associated with a diverse community of ectomycorrhizal (ECM) fungi. Amongst the 41 ECM fungal species detected in a 400 m2 P. dipterocarpacea ssp. nitida plot in Southern Venezuela, three species belonged to the Sebacinales. We tested whether ECM anatomotype characterization can be used as a feasible element in an integrative taxonomy in this diverse fungal group, where the relevance of fruitbody morphology for species delimitation seems limited. Using a combination of ECM morpho-anatomical characterizations and phylogenetic analyses based on nuclear ITS and LSU sequences, we report three new species. The main distinguishing features of Sebacina guayanensis are the yellowish cell walls together with conspicuous undifferentiated, uniform compact (type B) rhizomorphs. Staghorn-like hyphae are characteristic of S. tomentosa. The combination of clusters of thick-walled emanating hyphae, including hyphae similar to awl-shaped cystidia with basal dichotomous or trichotomous ramifications, and the presence of type B rhizomorphs were characteristic of a third, yet unnamed species. The three species belong to three different, possibly specifically tropical clades in Sebacinales Group A. The geographic distribution of phylogenetically related strains was wide, including a Dicymbe forest in Guyana and an Ecuadorian rainforest with Coccoloba species. We show that ECM morpho-anatomy can be used, in combination with other analyses, to delineate species within Sebacinales Group A. In addition to phylogenetic information, type B rhizomorphs observed in different Sebacinales clades have important ecological implications for this fungal group. The phylogeography of Sebacinales suggests that dispersion and host jump are important radiation mechanisms that shaped P. dipterocarpacea ECM fungal community. This study emphasizes the need for more sequence data to evaluate the hypothesis that phylogeographic relationships between neo- and paleotropical ECM fungal species could be attributed to the vicariance of cross-continental hosts such as the Dipterocarpacae.
帕卡拉伊马贝壳杉（Pakaraimaea dipterocarpacea）是贝壳杉科的一员，为圭亚那地区特有树种，与多种外生菌根（ECM）真菌群落相关。在委内瑞拉南部一块400平方米的亮叶帕卡拉伊马贝壳杉（Pakaraimaea dipterocarpacea ssp. nitida）样地中检测到的41种ECM真菌物种中，有3个物种属于角担菌目。我们测试了ECM解剖型特征是否可作为这个多样真菌类群综合分类学中的一个可行元素，在这个类群中，子实体形态对于物种界定的相关性似乎有限。通过结合ECM形态解剖特征以及基于核糖体DNA内转录间隔区（ITS）和大亚基（LSU）序列的系统发育分析，我们报告了3个新物种。圭亚那角担菌（Sebacina guayanensis）的主要鉴别特征是淡黄色的细胞壁以及明显未分化、均匀紧密的（B型）菌索。鹿角状菌丝是绒毛角担菌（S. tomentosa）的特征。厚壁发散菌丝簇，包括类似于锥状囊状体且基部有二叉或三叉分支的菌丝，以及B型菌索的组合是第三个尚未命名物种的特征。这3个物种属于角担菌目A组中3个不同的、可能是特定热带分支。系统发育相关菌株的地理分布广泛，包括圭亚那的双翅豆森林和厄瓜多尔有海葡萄属物种的雨林。我们表明，ECM形态解剖可以与其他分析相结合，用于界定角担菌目A组内的物种。除了系统发育信息外，在不同角担菌分支中观察到的B型菌索对这个真菌类群具有重要的生态意义。角担菌目的系统地理学表明，扩散和寄主转移是塑造帕卡拉伊马贝壳杉ECM真菌群落的重要辐射机制。这项研究强调需要更多的序列数据来评估新热带和古热带ECM真菌物种之间的系统地理关系可能归因于诸如龙脑香科等跨大陆寄主的隔离分化这一假设。
