PRF/J: Quantitative Genetics of Adaptation and Apparent "Constraint" in a Desert Annual

这项研究考察了模式系统Eriogonum ababtiamum的几个人口统计特征的遗传结构和潜在的生理机制，Eriogonum ababtiamum是一种沙漠一年生植物。这项工作旨在进一步了解生活史适应的遗传基础和明显的进化“制约”。索诺兰比奇瓦瓦沙漠更多的Eriogonum在春季开花，但这两个地区的种群都保留了双季节繁殖的祖先特征(春季和夏季)。人口统计学和遗传学研究表明，自然选择可能解释了索诺兰开花更早的原因。然而，双季性的保留与索诺兰种群的适应性解释并不一致：预期的夏季繁殖力并不超过季节间死亡的风险。化石、分布和生物地理证据也表明了同样的结论。田间和温室的初步研究表明，生活史性状之间的相关性可能会阻碍提高春季繁殖力的选择。选择实验被用来确定a)人口统计性状之间的遗传力和遗传相关性是否显著不同于零；以及b)对相关性本身的选择是否可以改变它们的符号，即相关性是否可以起到约束作用。SIB对生长和分配特征的分析--这是人口统计特征的基础--将检查这些特征在种群内和种群之间的遗传变异。

This research examines the genetic architecture of several demographic traits and underlying physiological mechanisms in the model systems Eriogonum abertiamum, a desert annual. The work is designed to further understanding of the genetic basis for life history adaptation and of apparent evolutionary "constraints." More Sonoran than Chihuahuan Desert Eriogonums begin flowering in spring, but populations in both regions retain the ancestral character of biseasonal reproduction (spring and summer). Demographic and genetic studies suggest that natural selection may explain earlier Sonoran flowering. However, retention of Biseasonality is not consistent with adaptive explanations in Sonoran populations: Expected summer fecundity does not outweigh the risk of between-season mortality. Fossil, distributional, and biogeographic evidence suggest the same conclusion. Correlations among life history traits may block selection for increased spring fecundity, as suggested by preliminary field and greenhouse studies. Selection experiments are proposed to determine a) whether heritabilities and genetic correlations among demographic traits are significantly different from zero; and b) whether selection on the correlations themselves can change their signs, i.e., whether the correlations can act as constraints. Sib analyses of growth and allocation traits--which underlie demographic traits--will examine genetic variation for these traits both within and between populations.