Dissertation Research: Sex Ratio in an Autoparasitoid Wasp

论文研究：自寄生蜂的性别比例

• 批准号: 8914634
• 负责人: David Pimentel
• 金额: --
• 依托单位: Cornell University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1990
• 资助国家: 美国
• 起止时间: 1990-02-15 至 1992-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8914634&HistoricalAwards=false
• 关键词: Dissertation; Research; Sex; Ratio; Autoparasitoid

The proportion of females in an animal species directly influences the rate of population growth, and thus is important for understanding population dynamics. Although equal numbers of each sex are produced in many animals, members of some groups, such as the parasitic wasps, often exhibit highly variable sex ratios. Understanding the mechanisms that produce these variable sex ratios is necessary to predict population fluctuations. In addition, variable sex ratios offer a good opportunity to study the process of adaptation, since optimal sex ratios can be predicted using evolutionary models, and the fit to theory can be easily measured experimentally. In a group of minute parasitic wasps in the family Aphelinidae females lay male and female eggs in different hosts. Female eggs are laid inside nymphs of Homoptera, such as whitefly and scale insects, while male eggs are laid inside the body of immature female wasps while they are still developing within the homopteran host. Males are parasitic on female wasps, often of their own species. This study involves investigating the sex allocation behavior of females of an autoparasitoid, Encarsia pergandiella, which parasitizes whiteflies. In particular, the investigator is investigating how females allocate eggs to be sons and daughters given the constraint on sex ratio imposed by the availability of the appropriate hosts. The pattern of egg laying in the two host will be examined over the season when the availability of the two hosts, and the density varies. In the laboratory, factors which may alter the sex allocation behavior such as host density, previous experience and female age will be examined. The results will be interpreted in the context of evolutionary theory. This system offers a unique opportunity to test sex ratio theory. Fisher predicted that natural selection should equalize the investment of resources in each sex. Generally this leads to a 1:1 sex ratio, but in autoparasitoids the predicted sex ratio varies with the limited resource. When eggs are limiting, sons and daughters should be produced in equal numbers, but when hosts are limiting, the sex ratio should reflect the relative availability of the two hosts. In addition, autoparasitoids have been used in many instances to biologically control scale and whitefly pests, often with tremendous economic and environmental benefits due to reduced numbers of pesticide applications. Sex ratio is central to the population biology of these wasps, and, therefore, an understanding of the mechanisms that control sex ratio will improve our ability to evaluate wasp species for their potential to control pest species.

动物物种中雌性的比例直接影响种群增长率，因此对于了解种群动态非常重要。 尽管许多动物中每种性别的数量相等，但某些群体的成员（例如寄生黄蜂）往往表现出高度可变的性别比例。 了解产生这些可变性别比例的机制对于预测人口波动是必要的。 此外，可变的性别比例为研究适应过程提供了一个很好的机会，因为可以使用进化模型预测最佳性别比例，并且可以通过实验轻松测量与理论的拟合度。 在蚜科的一群微小寄生蜂中，雌性在不同的宿主中产下雄性和雌性卵。 雌性卵产在同翅目若虫体内，例如粉虱和介壳虫，而雄性卵产在未成熟雌性黄蜂体内，当时它们仍在同翅目宿主体内发育。 雄性黄蜂寄生在雌性黄蜂身上，通常是同种的雌性黄蜂。 这项研究涉及调查寄生粉虱的自寄生蜂 Encarsia pergandiella 雌性的性别分配行为。 特别是，考虑到适当宿主的可用性对性别比例的限制，研究人员正在调查雌性如何将卵子分配给儿子和女儿。 当两个宿主的可用性和密度变化时，将在整个季节检查两个宿主的产卵模式。 在实验室中，将检查可能改变性别分配行为的因素，例如宿主密度、以前的经验和女性年龄。 结果将在进化理论的背景下进行解释。 该系统为检验性别比理论提供了独特的机会。 费舍尔预测，自然选择应该使每个性别的资源投资均等。 一般来说，这会导致 1:1 的性别比，但在自寄生蜂中，预测的性别比随有限的资源而变化。 当卵数有限时，儿子和女儿的产量应相等，但当寄主有限时，性别比例应反映两个寄主的相对可用性。 此外，自寄生蜂已在许多情况下用于生物控制介壳虫和粉虱害虫，由于减少了农药施用数量，通常会带来巨大的经济和环境效益。 性别比例是这些黄蜂种群生物学的核心，因此，了解控制性别比例的机制将提高我们评估黄蜂物种控制害虫物种潜力的能力。