The Genetic Basis of Sex Ratio Distortion in Silene Alba

虽然传统的性别比理论预测生物将产生大致相等的性别比例，但许多物种表现出持久的性别比例偏见。因此，现在存在着丰富多样的关于性别比例偏差的理论。减数分裂驱动、细胞质遗传和其他非孟德尔机制可能在性别比例偏差的进化中起主要作用。减数分裂驱动系统，包括性别比例扭曲，可能是我们理解进化过程的核心，如性染色体进化，性别决定机制的进化和多样性，以及物种间不育障碍的起源（包括霍尔丹规则）。最初的研究表明，一种雌雄异株植物——矽莲的某些科表现出严重的雌性偏倚性比例。涉及Y染色体分子标记的研究表明，过孔存在于种子中，因此，不是由于雄性后代的死亡率较高。性别比例偏差是通过父系遗传或表现出来的。这种遗传模式和其他间接证据使人们怀疑x连锁减数分裂驱动系统可能是导致女性偏见进化的原因。本研究将采用反向杂交和回交的方法，确定白丝藻性别比例扭曲的遗传基础。RAPD标记，将用于研究女性偏见是如何以及何时产生的。地理上分离的种群和亲缘关系密切的物种之间的杂交将用于检测性别比例扭曲，这种扭曲通常由修复者抑制。最后，将确定白丝兰自然种群的结构是否与性别比例偏倚的其他选择机制相一致。这些结果将为自然种群中影响性别比的遗传机制的性质和多样性提供信息。此外，由于性染色体标记和宽杂交是研究性别比遗传学的独特方法，预计这些方法将刺激对其他物种性别比偏倚机制的研究。

While traditional sex ratio theory predicts organisms will produce roughly equal proportions of the sexes, many species exhibit persistent sex ratio biases. Consequently, there now exists a rich diversity of theory pertaining to biased sex ratios. Meiotic drive, cytoplasmic inheritance and other non-Mendelian mechanisms of sex ratio distortion may play a major role in the evolution of biased sex ratios. Meiotic drive systems, including sex ratio distorters, may be central to our understanding of evolutionary processes such as sex chromosome evolution, the evolution and diversity of sex determining mechanisms, and the origin of sterility barriers between species (including Haldane's Rule). Initial research has shown that certain families of Silene alva, a dioecious plant, exhibit severely female biased sex ratios. Studies involving molecular markers of the Y chromosome show that the vias is present in the seed and is therefore, not due to a higher mortality of male progeny. Sex ratio bias is inherited through or expressed in the male parent. This pattern of inheritance and other circumstantial evidence lead one suspect and X-linked meiotic drive system may be responsible for the evolution of the female bias. The proposed research will determine the genetic basis of sex ratio distortion in Silene alba by using reciprocal crosses and backcrosses. RAPD markers, will be used to investigate specifically how and when the female bias develops. Crosses among geographically separated populations and among closely related species will be used to detect sex ratio distortion which is normally suppressed by restorers. Finally, whether the structure of natural populations of Silene alba is consistent with other mechanisms of selection for biased sex ratios will be determined. These results will provide information the nature and diversity of genetic mechanisms influencing sex ratio in natural populations. Moreover, because sex chromosome markers and wide crosses represent unique approaches to studying sex ratio genetics,it is expected that methods will stimulate research into mechanisms of sex ratio bias in other species.