Revision of leccinoid fungi, with emphasis on North American taxa, based on molecular and morphological data

The leccinoid fungi are boletes and related sequestrate mushrooms (Boletaceae, Basidiomycota) that have traditionally been placed in <i>Leccinum, Boletus, Leccinellum</i>, and a handful of other less familiar genera. These mushrooms generally feature scabers or scaber-like dots on the surface of the stipe, and they are often fairly tall and slender when compared with other boletes. They are ectomycorrhizal fungi and appear to be fairly strictly associated with specific trees or groups of related trees. In the present study, we investigate the phylogenetic relationships among the leccinoid fungi and other members of the family Boletaceae using portions of three loci from nuc 28S rDNA (28S), translation elongation factor 1-α (<i>TEF1</i>), and the RNA polymerase II second-largest subunit (<i>RPB2</i>). Two DNA data sets (combined 28S-<i>TEF1</i> and 28S-<i>TEF1-RPB2</i>), comprising sequences from nearly 270 voucher specimens, were evaluated using two different phylogenetic analyses (maximum likelihood and Bayesian inference). Five major clades were obtained, and leccinoid fungi appeared in four of them. Taxonomic proposals supported by our results, representing a broadly circumscribed <i>Leccinum</i> that includes several sequestrate genera, along with <i>Leccinellum</i>, are made.

类疣柄牛肝菌真菌（leccinoid fungi）是牛肝菌及相关闭囊壳类蘑菇，隶属于牛肝菌科（Boletaceae）、担子菌门（Basidiomycota），传统上被归类于疣柄牛肝菌属（Leccinum）、牛肝菌属（Boletus）、类疣柄牛肝菌属（Leccinellum）以及其他少数较为冷门的属。这类蘑菇的菌柄表面通常具疣点或类疣点结构，相较于其他牛肝菌，其个体往往更为修长高大。它们属于外生菌根真菌，似乎与特定树种或近缘树种类群存在严格的专性共生关联。本研究通过取自核28S核糖体DNA（nuc 28S rDNA，28S）、翻译延伸因子1-α（translation elongation factor 1-α，TEF1）以及RNA聚合酶II第二大亚基（RNA polymerase II second-largest subunit，RPB2）三个基因位点的片段序列，探究了类疣柄牛肝菌真菌与牛肝菌科其他类群之间的系统发育关系。研究构建了两组DNA数据集（合并的28S-TEF1数据集与28S-TEF1-RPB2数据集），涵盖近270份凭证标本的序列信息，并采用最大似然法（maximum likelihood）与贝叶斯推断法（Bayesian inference）两种不同的系统发育分析方法进行评估。分析结果共得到5个主要演化支，其中4个演化支包含类疣柄牛肝菌真菌类群。基于本研究结果，我们提出如下分类学修订建议：将若干闭囊壳类属纳入广义疣柄牛肝菌属（Leccinum）的界定范围，同时保留类疣柄牛肝菌属（Leccinellum）。