Molecular Systematics of Homobasidiomycetes Emphasizing Polyporaceae and Corticiaceae

同形孢子菌是一种多样的真菌，包括蘑菇、多孔菌、泡球菌、臭角菌、珊瑚菌等。许多物种腐烂死去的有机物，在养分循环中起重要作用。其他包括植物病原体、外生菌根（树根的共生伙伴）、地衣形成真菌，以及与节肢动物（如新热带的切叶蚁）的共生伙伴。尽管它们在生态和经济上具有重要意义，但它们的进化或系统发育关系尚不清楚。其中一个原因是，真菌在解剖学上很简单，因此它们表现出的特征很少，无法用于区分它们和推断分类关系。另一个令人困惑的因素是真菌的化石记录很差，尤其是肉质同源菌类。博士的研究。哈佛大学的Michael Donoghue和David Hibbett的目标是利用DNA序列确定同形孢子菌之间的进化关系。被测序的基因被称为rDNA，编码构成核糖体（参与蛋白质合成的细胞器）的核酸。这些rna在序列上是高度保守的，这使得它们对推断非常古老的进化分歧很有用。核和线粒体的dna都被测序，来自同一组范例分类群。这些序列彼此对齐，并使用计算机算法进行分析，该算法基于DNA序列中的变异模式（突变替代）来估计基因之间的关系。由此产生的进化假设被表示为系统发育树。本研究的重点是两大类同形孢子菌，即Polyporaceae和Corticiaceae。Polyporaceae包括具有多孔子实体的真菌，如许多“支架真菌”，而Corticiaceae包括具有简单的，复盖的（光滑的，壳状的）子实体的真菌。这两个科主要是根据一些宏观形态特征来划分的，但解剖学证据表明它们是由来自许多不同进化谱系的物种组成的。一个主要的问题是：形态学上简单的皮质类真菌是一种多形（原始）类群，其他更复杂的形式是从它衍生出来的，还是皮质类真菌是从更复杂的形式通过还原和简化而进化而来的？

9629427 Donoghue Homobasidiomycetes are a diverse group of fungi that includes mushrooms, polypores, puffballs, stinkhorns, coral fungi, and others. Many species decay dead organic matter and are important in nutrient cycling. Others include plant pathogens, ectomycorrhizae (symbiotic associates of tree roots), lichen-forming fungi, and mutualist partners with arthropods such as the leaf-cutter ants of the neotropics. Despite their ecological and economic importance, the evolutionary or phylogenetic relationships of homobasidiomycetes are not well understood. One reason for this is that fungi are anatomically simple, and hence they display few characters that could be useful for discriminating among them and inferring taxonomic relationships. Another confounding factor is the poor fossil record for fungi in general, and for fleshy homobasidiomycetes in particular. Research by Drs. Michael Donoghue and David Hibbett at Harvard University is directed toward the goal of determining evolutionary relationships among the homobasidiomycetes using DNA sequences. The genes to be sequenced, called rDNA, encode the nucleic acids that make up ribosomes (organelles involved in protein synthesis). The rDNAs are highly conserved in sequence, which makes them useful for inferring very ancient evolutionary divergences. Both nuclear and mitochondrial rDNAs are being sequenced, from the same set of exemplar taxa. The sequences are aligned to each other and analyzed using computer algorithms that estimate relationships among genes based on the pattern of variation (mutational substitutions) in their DNA sequences. The resulting evolutionary hypothesis is represented as a phylogenetic tree. Two main groups of homobasidiomycetes are the focus of this research, the Polyporaceae and the Corticiaceae. The Polyporaceae includes fungi with poroid fruiting bodies such as many "bracket fungi", whereas the Corticiaceae includes fungi that have simple, resupinate (smooth, crust-like) fruiting bodies. Both families are de limited primarily on the basis of a few macromorphological features, but anatomical evidence suggests that they are composed of species from many different evolutionary lineages. One major question being addressed is: are the morphologically simple corticioid fungi a plesiomorphic (primitive) group from which other more complex forms have been derived, or have the corticioid forms evolved by reduction and simplification from more elaborate forms?