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首页> 外文学位 >Geographic variation and natural selection on a leaf shape polymorphism in the ivyleaf morning glory (Ipomoea hederacea).
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Geographic variation and natural selection on a leaf shape polymorphism in the ivyleaf morning glory (Ipomoea hederacea).

机译：常春藤牵牛花（Ipomoea hederacea）叶片形状多态性的地理变异和自然选择。

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摘要

The ivyleaf morning glory, (Ipomoea hederacea) has a genetic polymorphism in leaf shape: some plants have lobed leaves, while others possess entire, unlobed leaves. Leaf shape variation of this magnitude may affect plant water relations and herbivore preference, and is thus likely to be experiencing selection. However, no studies have yet demonstrated that leaf morphs which are predicted to be favored in a particular environment are actually favored. I have investigated the action of natural selection on and the causative agents affecting this leaf shape polymorphism. I used three different approaches. As a first step, I identified the geographic pattern of leaf shape variation. Second, to determine if natural selection was responsible for this pattern, I measured the pattern of selection acting at three sites which spanned this geographic variation. Third, to determine the cause of this pattern, I identified the agents of selection.;First, using herbarium collections and population surveys, I determined that leaf shape variation in this species is spatially segregated: only lobed plants are found in the northern part of the species range, while in the south, both lobed and entire plants are found. Second, using perturbation field experiments, I measured the pattern of natural selection over an area that spanned this geographic variation. I found directional selection in a "lobed-only" site one year, and heterozygous advantage at the same site the next year. At two sites further south, I found heterozygous advantage. This pattern of selection is consistent with the geographic pattern, suggesting that natural selection is, in part, responsible for the observed pattern of geographic variation. Third, I measured environmental correlates to leaf shape variation in I. hederacea, to formalize hypotheses of the potential agents of selection. I then explicitly tested the hypotheses that water availability and white rust are agents of selection. Water availability was not found to be an agent of selection on this polymorphism in two experiments designed to explicitly test this hypothesis. However, the white rust fungus, Albugo ipomoeae-panduranae, was found to be an agent of selection. This study suggests that leaf shape has a previously unconsidered function: resistance to pathogens.
机译：常春藤牵牛花（Ipomoea hederacea）具有叶片形状的遗传多态性：有些植物有浅叶，而另一些则有完整的无叶。如此大小的叶片形状变化可能会影响植物的水分关系和草食动物的喜好，因此很可能正在经历选择。但是，尚无研究表明预计在特定环境中有利的叶片变体实际上是有利的。我研究了自然选择对叶形多态性的作用及其病因。我使用了三种不同的方法。第一步，我确定了叶片形状变化的地理模式。其次，为了确定自然选择是否是这种模式的原因，我测量了跨越这种地理变化的三个地点的选择模式。第三，确定这种模式的原因，我确定了选择的原因。首先，使用植物标本室收集和人口调查，我确定了该物种的叶片形状变化在空间上是隔离的：仅在北半球发现了有叶的植物。种类繁多，而在南部，既有叶也有整个植物。其次，我使用摄动场实验测量了跨越这种地理变化的区域内自然选择的模式。我发现一年在“仅叶状”站点进行定向选择，第二年在同一站点进行杂合优势。在更南的两个地点，我发现了杂合优势。这种选择模式与地理模式相一致，表明自然选择在某种程度上负责观察到的地理变异模式。第三，我测量了环境与Hederacea中叶片形状变化的相关性，以使选择潜在因素的假设正式化。然后，我明确检验了水可用性和白锈病是选择因素的假设。在旨在明确检验该假设的两个实验中，没有发现水的可用性是该多态性的选择因素。然而，发现白锈真菌Albugo ipomoeae-panduranae是选择的媒介。这项研究表明，叶片形状具有以前未被考虑的功能：对病原体的抗性。

著录项

  • 作者

    Bright-Emlen, Kerry Leigh.;

  • 作者单位

    Duke University.;

  • 授予单位 Duke University.;
  • 学科 Ecology.;Botany.;Genetics.
  • 学位 Ph.D.
  • 年度 1998
  • 页码 107 p.
  • 总页数 107
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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