Dissertation Research: Evolution of Female/Male Ratio in Gynodioecious Nemophila Menziesii

[00:73550]韦勒巴尔雌雄同体植物种群中雌性的出现一直是一个令人困惑的进化现象，因为与雌雄同体相比，雌性似乎在基因传播方面遭受了损失。另一个难题是，女性的频率在短距离和时间尺度上变化很大。在许多物种中，性别是由核基因和细胞质基因的相互作用决定的。已经提出的解释女性频率变异的一种机制是细胞质男性不育（雌性引起）和核男性生育恢复（雌雄同体引起）基因的重复基因流动以及这两个基因组亚群之间的利益冲突。这种基因流动模型将在一种一年生植物menziesii上进行测试，该植物显示出雌性频率的相当大的变化。基因流动的另一种假设，即雌性对雌雄同体适合度的影响及其如何影响雌性频率动态，也将被研究。提出了第三个实验来确定核恢复等位基因的传播遗传学。最后，杂交导致雌性在大地理范围内出现的作用将被检查。理论研究表明，基因冲突可能是导致大量进化现象的原因。细胞质雄性不育是研究得最好的基因组冲突之一，主要是因为它在农业杂交种子生产中的应用。然而，除了对少数模型系统的研究之外，还没有建立起影响自然系统性别比例的基因组冲突动力学。这项关于门氏线虫的研究将测试新的模型，并将先前的研究与基因组冲突理论联系起来。细胞质雄性不育的遗传学也将进行研究。最后，在门齐氏奈瑟氏菌中看到的区域性别比变化是一个独特的特征，可以检查大规模的性别比过程。

0073550Weller & BarrThe appearance of females in hermaphroditic plant populations has been a puzzling evolutionary phenomenon because females would appear to suffer in gene transmission compared with hermaphrodites. Another puzzle is that female frequencies can vary considerably over short distances and time scales. In many species, sex is determined by an interaction between nuclear and cytoplasmic genes. One mechanism that has been proposed to explain female frequency variation is repeated gene flow of cytoplasmic male sterility (female-causing) and nuclear male fertility restoring (hermaphrodite-causing) genes and a conflict of interest between these two genomic subsets. This gene flow model will be tested with an annual plant, Nemophila menziesii, which shows considerable variation in female frequency. An alternative hypothesis to gene flow, the effect of females on hermaphrodite fitness and how that affects female frequency dynamics, will also be investigated. A third experiment is proposed to determine transmission genetics of nuclear restorer alleles. Finally, the role of hybridization leading to the appearance of females on a large geographic scale will be examined.Theoretical work has shown that genomic conflicts may be the cause of a large array of evolutionary phenomena. Cytoplasmic male sterility is one of the best studied genomic conflicts largely because of its use in agricultural hybrid seed production. However, outside of work on few model systems, the dynamics of genomic conflicts affecting sex ratios in natural systems has not been established. This study of Nemophila menziesii will test new models and tie in previous work with genomic conflict theory. The genetics of cytoplasmic male sterility will also be investigated. Finally, the regional sex ratio variation seen in N. menziesii is a unique feature that allows for an examination of large-scale sex ratio processes.