Morphological and Ecological Diversification In the Homobasidiomycetes: A Molecular Phylogenetic Analysis

[9903835] hibbett和Donoghue同形孢子菌包括蘑菇形成真菌及其亲戚。已知的真菌种类约有13500种，约占所有已知真菌种类的23%。同担子菌的子实体包括明显的、发育完整的结构，如蘑菇和泡球，以及非常简单的形式，如“皮质”真菌的外壳状子实体。同形担子菌在陆地生态系统碳循环中起主要作用；它们包括大多数木材腐烂真菌和外生菌根真菌（与树根有关）；它们还包括分枝寄生虫、昆虫共生体、地衣和凋落物分解者。虽然这些真菌的个别群体已经被深入研究，但它们的形态和生态进化的总体模式尚未确定，因为迄今为止还没有广泛的系统发育框架支持该群体。近年来，通过利用新的DNA序列特征，特别是编码核和线粒体核糖体RNA （rDNA）的基因，在了解同形孢子菌的系统发育方面取得了相当大的进展。该项目将扩大核和线粒体rDNA序列数据库，并增加正在研究的蛋白质编码基因的新数据，如小管蛋白或RNA聚合酶。分类群取样将针对有问题的类群，如多孔类、膜壳类和花花素类，这些类群的关系仍然没有得到现有分子数据的有力支持。系统发育分析的常规方案将被采用，此外，研究者将探索使用“超级树”来组合或整理独立的系统发育树与重叠的分类群，以构建一个复合的系统发育假设。这些树将用于构建系统发育分类，并研究选择的形态和生态特征的历史进化模式。需要研究的具体性状包括：皮质型和直立型子实体；木材腐烂的褐腐与白腐模式；以及外生菌根与腐殖质和致病性的营养模式。一个广泛的框架系统发育的同形孢子菌将有助于，例如，通过识别姐妹群和最近的外群，更深入地分析这些真菌的形态和生理变化。

9903835Hibbett and Donoghue Homobasidiomycetes include the mushroom-forming fungi and their relatives. About 13,500 species have been described, which is about 23% of all known species of fungi. The fruiting bodies of homobasidiomycetes include conspicuous, developmentally integrated structures such as mushrooms and puffballs, as well as very simple forms such as the crust-like fruiting bodies of "corticioid" fungi. Homobasidiomycetes play major roles in carbon cycling in terrestrial ecosystems; they comprise the majority of wood-decay fungi and ectomycorrhizal fungi (associated with tree roots); and they also include mycoparasites, insect symbionts, lichens, and litter decomposers. Although individual groups of these fungi have been studied intensively, their overall pattern of morphological and ecological evolution has not been determined because to date there has existed no broad well-supported phylogenetic framework for the group. Over the last few years, considerable progress has been made in understanding homobasidiomycete phylogeny through the use of new DNA sequence characters, particularly the genes encoding nuclear and mitochondrial ribosomal RNA (rDNA). This project will expand the database of nuclear and mitochondrial rDNA sequences and add new data from protein-coding genes under study, such as the tubulins or RNA polymerases. Taxon sampling will target problematic groups such as the polyporoid, hymenochaetoid, and cantharelloid groups of fungi, whose relationships remain weakly supported by the existing molecular data. Conventional protocols for phylogenetic analyses will be employed, and in addition the investigators will explore the use of "supertrees" for combining or collating independent phylogenetic trees with overlapping sets of taxa in order to construct a composite phylogenetic hypothesis. The trees will be used to construct phylogenetic classifications and to study historical patterns of evolution in selected morphological and ecological characters. Specific characters to be investigated include: corticioid versus erect fruiting bodies; brown rot versus white rot modes of wood decay; and ectomycorrhizal versus saprotrophic and pathogenic modes of nutrition. A broad framework phylogeny for the homobasidiomycetes will facilitate, for example by identifying sister groups and nearest outgroups, more intensive analyses of morphological and physiological changes in these fungi.