Collaborative Proposal: Integrating Morphological and Molecular Systematics of Alternaria and Related Fungal Genera

0416314Peever 链格孢属真菌物种在植物病害、食品毒理学、医学真菌学和生态学方面具有重要的经济意义，但尚未使用现代 DNA 分析工具对这一大型属进行全面研究。迫切需要一个可行的分类系统，以确保物种鉴定的一致和可靠，并促进比较生物学的高级研究。为此，亚利桑那大学的 Barry Pryor 和华盛顿州立大学的 Tobin Peever 合作的主要目标是：1）根据多个基因 DNA 序列的比较，建立链格孢属物种之间的进化关系；2）根据物种内种群之间 DNA 的比较，重新检查并建立界定链格孢属物种的新标准；3）评估通过 DNA 分析验证的严格定义物种的形态特征。这些目标中还包含其他目标，即根据形态特征创建可供研究、行业和监管专业人员使用的分类识别码，并开发一个在线数据库来传播这些研究和其他相关研究生成的数据。该数据库将作为促进链格孢属和相关真菌当代研究进展的全球资源。拟议的研究范围对于无性繁殖真菌的进化来说既及时又全面，其中链格孢属是主要代表。一般来说，大多数生物体的分类主要基于有性结构的发育和特征，这些结构通常已被证明与基于 DNA 分析的进化关系一致。因此，无性真菌研究的主要局限性之一是缺乏有性结构。直到最近，研究才开始检查无性真菌的特征，并将其与 DNA 分析数据进行对比。然而，这些研究很少涉及种群之间的种内变异，这对于划定物种之间的界限至关重要。在链格孢属中，无性性状中存在相当大范围的特异性间和特异性多样性。此外，许多链格孢属物种在大片地理区域的出现为全面研究种内变异提供了理想的机会。因此，链格孢属形态特征的多样性为检验与无性特征进化意义相关的假设以及比较无性真菌基于形态的分类学与基于DNA的分类学提供了肥沃的土壤。将无性真菌有效整合到与有性真菌共同的进化框架中是全世界真菌学研究广泛认可的目标。对链格孢属的全面研究将为这一目标做出重大贡献。更重要的是，链格孢属无性谱系内物种的多样性和进化使这项研究成为未来研究塑造无性真菌谱系和一般无性生物的进化过程的基础。

0416314Peever Species of the fungus genus Alternaria are economically important in plant disease, food toxicology, medical mycology, and ecology, yet this large genus has not been comprehensively studied using modern tools of DNA analysis. A workable taxonomic system is critically needed that will ensure consistent and reliable identification of species and promote advanced studies in comparative biology. Toward this end, the principal objectives of collaborative work by Barry Pryor at University of Arizona and Tobin Peever at Washington State University are to: 1) establish evolutionary relationships among Alternaria species based upon comparison of DNA sequences from several genes, 2) re-examine and establish new criteria for delimiting Alternaria species based upon comparison of DNA among populations within species, and 3) evaluate morphological characters that critically define species validated by DNA analysis. Embedded within these objectives are additional goals of creating taxonomic identification keys based upon morphological characters that can be used by research, industry, and regulatory professionals, and developing an on-line database for the dissemination of data generated from these and other related studies. This database will serve as a world-wide resource for the advancement of contemporary research on Alternaria and related fungi. The scope of the proposed research is both timely and comprehensive in regard to the evolution of asexually-reproducing fungi, of which Alternaria is a key representative. In general, taxonomy for most organisms is based primarily on the development and characteristics of sexual structures, which normally have proven to be consistent with evolutionary relationships based upon DNA analyses. Thus, one of the primary limitations in the study of asexual fungi is the lack of sexual structures; only recently have studies begun to examine and contrast the characteristics of asexual fungi with data derived from DNA analysis. However, these studies seldom address intra-specific variation among populations, which is critical for delimiting the boundaries between species. Within Alternaria, a considerable range of inter- and intra specific diversity exists in asexual characters. Moreover, the occurrence of many Alternaria species over large geographic areas provides an ideal opportunity for comprehensive studies on intra-specific variation. Thus, the diversity in morphological traits encompassed within Alternaria provides a fertile ground for testing hypotheses relating to the evolutionary significance of asexual characters, and for comparing morphology-based taxonomy with DNA-based taxonomy of asexual fungi. The effective integration of the asexual fungi into a common evolutionary framework with the sexual fungi is a widely recognized goal of mycological research worldwide. A comprehensive study of Alternaria will contribute significantly to this objective. More importantly, the diversity and evolution of species within the asexual lineage of Alternaria positions this study as a foundation for future research into evolutionary processes that shape asexual fungal lineages and asexual organisms in general.