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首页> 外文学位 >An evolutionary and demographic analysis of life history variation in Campanula americana (Campanulaceae).
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An evolutionary and demographic analysis of life history variation in Campanula americana (Campanulaceae).

机译：桔梗生活史变化的进化和人口统计学分析。

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The coexistence of diverse life histories within natural populations may arise from a combination of ecological and evolutionary processes. As yet, a complete theory of life history evolution that integrates multivariate selection, genetics, and age-structured populations does not exist and few empirical studies of natural populations have been conducted. Therefore, I use a demographic matrix model and an analysis of phenotypic selection on life history traits to address the maintenance of winter annuals and biennials within populations of the monocarpic plant, Campanula americana. The frequency of the types within two Michigan populations, survivorship and fecundity over four generations, and the presence of a seed bank are documented.; I describe a general and systematic procedure for deriving demographic loops for the life history types from the structure of the life cycle graph. Biennial loop elasticities are over 90% in 6 of the 8 data sets examined, indicating higher relative fitness of biennials and consistent with the greater frequency of biennials in these two populations. However, winter annuals had higher survivorship in at least one year in one of the populations, suggesting temporal variation in the relative performance of the life history types.; Experimental seed cages indicated that newly dispersed seed delayed germination, suggesting that the fall emerging winter annuals may be older than one year. Simulations of the seed bank dynamics demonstrate that the fraction of spring vs. fall emergence plays an important role in determining the relative contributions of winter annual and biennial life history pathways to the population growth rate.; Selection on size and time of emergence varied in magnitude and direction among populations, episodes in the life cycle, and within populations. In one population, selection favored earlier emergence in the experimental cages but later emerging seedlings in the area surrounding the cages. Selection acting early in the life time favored larger rosettes, generally biennials, but later this was offset by stabilizing selection on plant height.; I conclude that temporal and spatial variation in selection acting in concert with the age structure produced by the seed bank maintains the two life history types within populations.
机译：自然种群中多种生活史的共存可能源于生态过程和进化过程的结合。迄今为止，还没有一个完整的关于生命历史进化的理论，该理论将多元选择，遗传学和年龄结构化的种群整合在一起，并且很少进行对自然种群的实证研究。因此，我使用人口统计学矩阵模型和对生活史特征的表型选择分析来解决单株植物美国风铃草种群中冬季一年生和两年生的维持问题。记录了密歇根州两个种群中类型的发生频率，四代人的存活率和繁殖力以及种子库的存在。我描述了一种从生命周期图的结构中得出生命史类型的人口统计环的通用系统过程。在所检查的8个数据集中的6个数据集中，两年一次的回圈弹性超过90％，表明两年一次的相对适应性较高，并且与这两个人群中两年一次的频率较高相符。然而，其中一种种群的冬季一年至少有较高的存活率，这表明生活史类型的相对表现在时间上存在差异。实验性的种子笼表明，新分散的种子延迟了发芽，这表明秋季的冬季冬季一年生可能大于一年。对种子库动力学的模拟表明，春季与秋季出苗的比例在确定冬季年度和两年期生活史途径对种群增长率的相对贡献中起着重要作用。种群大小，生命周期的发作以及种群内部，出现的大小和时间的选择在大小和方向上都不同。在一个种群中，选择有利于较早出现在实验笼中，但较晚出现在笼周围的幼苗。在生命周期的早期进行选择时，倾向于选择较大的莲座丛，一般是两年生一次，但后来通过稳定株高选择来抵消。我得出的结论是，选择的时空变化与种子库产生的年龄结构保持一致，从而在种群内维持了两种生活史类型。

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