Dissertation Research: Parental Control of Sex Ratio in Haplodiploid Herbivores

众所周知，许多具有单倍体遗传系统的生物会优先分配雄性和雌性给个体后代，以响应不同的环境条件，使两性都有优势。（单倍体物种是一种性别的个体——通常是雄性——由未受精卵产生，而受精卵产生异性个体的物种）。例如，寄生蜂很可能会在一个相对较大的高质量的猎物个体中产卵一个雌性（受精卵），因为产卵的雌性可以通过大型，健壮的女儿胜过健壮的儿子。相比之下，雌性可能会通过小男孩而不是小女孩获得更多的后代，因此很可能会将雄性（未受精的）卵子分配给小的、低质量的寄主。上述形式的性别分配差异在寄生蜂中得到了很好的研究。然而，影响单倍体食草动物性别分配的因素知之甚少，尽管这些食草动物很常见，而且经常造成重大的经济损失(例如，蜘蛛螨和锯蝇)。此外，在许多单倍体群体中，食草性可能是一种原始状态，对性别控制的理解将有助于更好地理解食草性的进化。本研究将探讨单倍体食草动物的性别分配与所遇到的寄主植物质量的关系。通过研究不同的单倍体食草动物群体，如锯蝇和蜘蛛螨，单倍体是独立产生的，研究人员希望确定导致这种遗传系统成功的进化普遍性。这项研究的另一个方面是人口性别比与人口增长率的关系。通过确定导致雌性比例相对较高的寄主-植物因素，研究人员还将开始确定导致单倍体食草动物周期性爆发的寄主植物因素。除了存活率、生长率和产蛋量之外，种群中雌性的相对比例也是一个参数，可能对种群增长率产生重大影响。通过操纵寄主植物来改变单倍体食草动物的性别比例的能力可能会为控制农业和林业中的许多害虫提供一种额外的方法。​*** //

Many organisms possessing a haplodiploid genetic system are known to preferentially allocate maleness and femaleness to individual offspring in response to environmental conditions that differentially confer advantages to either sex. (A haplodiploid species is one in which individuals of one sex--usually males--are produced from unfertilized eggs, while fertilized eggs produce individuals of the opposite sex). For instance, parasitic wasps will most likely oviposit a female (fertilized) egg in a relatively large high quality prey individual since the ovipositing female stands to gain more grandoffspring through the function of large, robust daughters than through the function of large sons. In contrast, the female will probably gain more grandoffspring through the function of small sons than through small daughters and will thus most likely allocate male (unfertilized) eggs to small, low quality, hosts. Differential sex allocation of the form just described is well-studied in the parasitic wasps. However, the factors affecting sex allocation in haplodiploid herbivores are much less understood, though these herbivores are very common and quite often cause major economic damage (e.g., spider mites and sawflies). In addition, herbivory is probably a primitive state in many haplodiploid groups and an understanding of gender control will allow a better understanding of the evolution of herbivory. The proposed research will examine the relationship between sex allocation in haplodiploid herbivores and the variable quality of host-plants encountered. By examining diverse groups of haplodiploid herbivores, i.e., sawflies and spider mites, in which haplodiploidy arose independently, the investigators hope to define the evolutionary generalities that led to the success of this genetic system. A further aspect of this research is the relationship of population sex ratios to rates of population increase. By determining host-plant factors that result in the production of relatively greater proportions of females, the investigators will also begin to determine the host-plant factors responsible for periodic outbreaks of haplodiploid herbivores. In addition to survivorship, growth rate and egg production, the relative proportion of females in a population is a parameter with potentially large consequences for population growth rates. The ability to alter the sex ratio of hapodiploid herbivores through manipulation of their host plants could lead to an additional method of controlling many pests in agriculture and forestry. *** //