Post glacial reticulate evolution: phylogeography of Packera in western North America

冰期后网状进化：北美洲西部Packera的系统发育地理学

• 批准号: 45984-2008
• 负责人: Bain, John
• 金额: $ 1.09万
• 依托单位: University of Lethbridge
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2010
• 资助国家: 加拿大
• 起止时间: 2010-01-01 至 2011-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=451022
• 关键词: Post; glacial; reticulate; evolution; phylogeography

Packera, a genus of 50+ species in the Asteraceae (Daisy) family, is an ideal group for studies aimed at understanding the evolutionary history of the North American flora because (i) it is widespread in North America, with species occurring in all the major biomes (ii) many of the species are poorly defined due to apparent hybridization and introgression so that patterns of hybridization and resulting gene flow can both be examined in a range of historical and geographical contexts and (iii) high levels of intrapopulational chloroplast DNA (cpDNA) haplotype diversity provide a source of molecular markers than can be analyzed in a phylogenetic context. Packera originated in Mexico and has diversified there, in the Great Plains, the arctic and along the North American west coast. We will examine evolutionary patterns in all these regions to better assess the role of geographical isolation, natural selection, hybridization, refugial survival and species migration in the evolution of the flora. We will examine molecular divergence of both nuclear and cpDNA from the two Mexican mountain ranges where Packera diverged to determine whether this, followed by northern migration and widespread hybridization would explain the basis for the cpDNA diversity observed in many northern taxa. In the arctic, we will assess the importance of refugial survival followed by migration and recent hybridization, while in the Great Plains, we believe widespread species show patterns of high haplotype diversity that may be interpretable in the context of post-glacial migration patterns and resultant hybridization among newly overlapping species. Along the west coast two factors appear important; (i) serpentine soils have shaped the evolution of numerous plant groups including Packera by exerting selection for edaphic tolerance among colonizers and (ii) various coastal refugia may have provided a source of genetic diversity for post-glacial colonizing species throughout this region. Our phylogeographic studies of Packera over the next five years, will improve our understanding of the evolutionary importance of all of these factors and thereby greatly improve our understanding of factors affecting the evolution of the North American flora.

Packera 是菊科（雏菊）家族中包含 50 多个物种的属，是旨在了解北美植物区系进化历史的研究的理想群体，因为（i）它在北美广泛分布，物种出现在所有主要生物群落中（ii）由于明显的杂交和基因渗入，许多物种的定义不明确，因此可以在一系列条件下检查杂交模式和由此产生的基因流。 历史和地理背景以及 (iii) 高水平的群体内叶绿体 DNA (cpDNA) 单倍型多样性提供了可以在系统发育背景下进行分析的分子标记来源。 Packera 起源于墨西哥，并在墨西哥大平原、北极和北美西海岸实现多元化发展。我们将研究所有这些地区的进化模式，以更好地评估地理隔离、自然选择、杂交、避难生存和物种迁移在植物区系进化中的作用。我们将检查 Packera 分化的两个墨西哥山脉的核和 cpDNA 的分子分歧，以确定这种情况以及随后的北方迁移和广泛杂交是否可以解释在许多北方类群中观察到的 cpDNA 多样性的基础。在北极，我们将评估避难所生存以及迁徙和最近杂交的重要性，而在大平原，我们相信广泛分布的物种表现出高单倍型多样性的模式，这可以在冰河后迁徙模式和新重叠物种之间由此产生的杂交的背景下进行解释。在西海岸，有两个因素显得很重要： (i) 蛇纹土通过对殖民者之间的土壤耐受性进行选择，塑造了包括 Packera 在内的许多植物群的进化；(ii) 各种沿海避难所可能为整个地区的冰河后殖民物种提供了遗传多样性的来源。 未来五年我们对 Packera 的系统发育地理学研究将提高我们对所有这些因素的进化重要性的理解，从而极大地提高我们对影响北美植物区系进化的因素的理解。