Geml József, Laursen Gary A, Taylor D Lee
Institute of Arctic Biology, 311 Irving I Building, 902 N. Koyukuk Drive, P.O. Box 757000, University of Alaska at Fairbanks, Fairbanks, Alaska 99775, USA.
Mycologia. 2008 Jul-Aug;100(4):577-89. doi: 10.3852/07-042r1.
We provide a phylogenetic diversity assessment study in genus Agaricus as part of our ongoing work to saturate ITS and LSU rDNA sequence diversity of soil-dwelling fungi in Alaska. Pairwise sequence similarity-based groupings and statistical parsimony analyses were applied to delimit operational taxonomic unit (OTU) and were compared to results of full phylogenetic analyses. Our results show that the proportion of section Arvenses taxa is particularly high in the boreal forest and hypo-arctic (low arctic) regions, whereas the genus is represented by section Agaricus in high arctic habitats. Furthermore our findings suggest that the commercially important A. bisporus occurs naturally in the boreal region of interior Alaska, substantially expanding the known northern limit of the species. Delimitations of OTU varied greatly with different methods. In general 95% similarity-based grouping proved to be the least sensitive method, often resulting in section- and subsection-level groups. The 95% connection-limit statistical parsimony separated far more groups. The 98% similarity-based groups and the 98% connection limit networks recognized respectively 11 and 13 OTU containing our specimens. The 98% connection limit statistical parsimony was the only method in which all recognized OTU consisted of members grouped by branches with significant (> .95) posterior probabilities, providing an independent support for the groups. Our results also point out that considerable additional efforts will be needed to elucidate the evolution of this diverse genus and to assess its phylogenetic diversity, given that most taxa in our analyses could not be placed convincingly within well characterized species using ITS/LSU data.
作为我们持续开展的一项工作的一部分，我们对蘑菇属进行了系统发育多样性评估研究，该工作旨在使阿拉斯加土壤真菌的ITS和LSU rDNA序列多样性达到饱和。基于成对序列相似性的分组和统计简约分析被用于界定操作分类单元（OTU），并与完整系统发育分析的结果进行比较。我们的结果表明，在北方森林和亚北极（低北极）地区，阿文西组的分类单元比例特别高，而在高北极栖息地，该属由蘑菇组代表。此外，我们的研究结果表明，具有商业重要性的双孢蘑菇自然存在于阿拉斯加内陆的北方地区，大大扩展了该物种已知的北界。不同方法对OTU的界定差异很大。一般来说，基于95%相似性的分组被证明是最不敏感的方法，常常导致组的划分到组和亚组水平。95%连接限制的统计简约分析划分出的组更多。基于98%相似性的组和98%连接限制网络分别识别出包含我们标本的11个和13个OTU。98%连接限制的统计简约分析是唯一一种所有识别出的OTU都由后验概率显著（>.95）的分支分组的成员组成的方法，为这些组提供了独立支持。我们的结果还指出，鉴于我们分析中的大多数分类单元使用ITS/LSU数据无法令人信服地归入特征明确的物种，需要付出相当大的额外努力来阐明这个多样化属的进化并评估其系统发育多样性。
