Phylogeny of Laboulbeniales (Ascomycetes)

9615520布莱克韦尔分类目Laboulbeniales包括微小真菌，它们是各种节肢动物宿主上的专性体外寄生虫。它们奇特的形态和有趣的生态关系使它们成为进化研究的迷人对象。虽然真菌学家和昆虫学家在一般意义上都知道，但这些显著的子囊菌几乎没有引起持续的研究，而且对大约2000个命名物种的分类是不稳定的。作为一个群体，唇形菌目的特征是缺乏大多数真菌体内典型的管状丝状物(菌丝体)，而是具有少数细胞体，这些细胞体由有性孢子分裂而开始，然后是吸器，通过节肢动物的寄主角质层生长以获取营养。由于唇形目细菌通常在交配时通过寄主接触而传播，因此它们的过程和结构可能会触发孢子的排出。这组真菌的形态是如此不同寻常，以至于它们曾被认为是红藻的寄生后代。它们耐人寻味的生活史特征为系统发育分析提供了许多形态特征，但尚未进行这种明确的研究。目前的研究借鉴了Meredith Blackwell教授之前关于子囊菌的工作，这些子囊菌具有更典型的形态和生活史，包括在其他真菌和节肢动物上的寄生阶段。系统发育工作将包括研究核糖体DNA的形态特征、生活史阶段和核苷酸序列多样性，以此作为分类解析和谱系重建的特征来源。为该目的属和科建立一个系统发育框架，从而改进分类，是一个主要目标。另一个目标是探索不同节肢动物寄主上的唇形目动物群体之间的寄主转移和物种形成的假说。

9615520 Blackwell The taxonomic order Laboulbeniales includes minute fungi that are obligate ectoparasites on a variety of arthropod hosts. Their bizarre morphology and interesting ecological relationships make them fascinating subjects for evolutionary investigation. Although known in a general sense to mycologists and entomologists, these remarkable ascomycetes have attracted little sustained study, and the taxonomic classification of the c. 2,000 named species is unstable. As a group, the Laboulbeniales are characterized by the absence of the tubular threads (mycelia) typical of the bodies of most fungi, but instead possess few-celled bodies that are initiated by division of the sexual spores, followed by haustoria that grow through the arthropod host cuticle to obtain nutrients. Because they are dispersed through host contact, often during mating, species of Laboulbeniales often have processes and structures that may act as triggers for spore discharge. So unusual is the morphology of this group of fungi that they were once proposed as parasitic descendants of the red algae. The intriguing features of their life cycle provide many morphological characters for phylogenetic analysis, but no such explicit study has yet been undertaken. The current study draws upon Prof. Meredith Blackwell's previous work with putatively related ascomycete fungi with more typical morphology and with life cycles that include parasitic stages on both other fungi and arthropods. The phylogenetic work will include studies of morphological features, of life history stages, and of nucleotide sequence diversity in nuclear ribosomal DNA as a source of characters for taxonomic resolution and genealogical reconstruction. A phylogenetic framework for the genera and families of the order, with consequent improvement in classification, is one major goal. Another goal is to explore hypotheses of host-shifting and speciation among groups of Laboulbeniales on different arthropod hosts.