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

两性植物种群中雌性的出现一直是一个令人费解的进化现象，因为与两性植物相比，雌性植物似乎会遭受基因传递的痛苦。另一个难题是，女性的频率在短距离和时间尺度上可能会有很大的差异。在许多物种中，性别是由核基因和细胞质基因之间的相互作用决定的。已提出的一种解释雌性频率变异的机制是细胞质雄性不育(雌性引起)和核雄性育性恢复(两性引起)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。这一基因流模型将在一年生植物门氏莲子草上进行测试，该植物在雌性频率上显示出相当大的差异。还将研究基因流动的另一种假说，即雌性对两性适合性的影响，以及这如何影响雌性频率动态。第三个实验是为了确定核恢复等位基因的传递遗传学。最后，我们将考察杂交在大地理范围内导致雌性出现的作用。理论工作表明，基因组冲突可能是一系列进化现象的原因。细胞质雄性不育是研究最多的基因组冲突之一，这在很大程度上是因为它在农业杂交制种中的应用。然而，除了在少数几个模型系统上的工作外，基因组冲突对自然系统中性别比例的影响还没有建立起来。这项对门氏线虫的研究将测试新的模型，并与之前的基因组冲突理论相结合。细胞质雄性不育的遗传学也将被研究。最后，在N.menziesii中看到的地区性比变化是一个独特的特征，它允许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.