Dissertation Research: Quantitative Genetics of a Parasitic Wasp

在大多数物种中，儿子和女儿的数量是相等的，这种1:1的性别比例通常存在于大型随机交配种群的动物中。甚至性别比例也是染色体性别决定的结果（例如哺乳动物，雌性是XX，雄性是XY）。在具有这种性别决定的动物中，性别比例很少或没有遗传变异。然而，在膜翅目昆虫（蜜蜂、蚂蚁和黄蜂）中，性别不是这样决定的；雌性后代来自受精卵，雄性后代来自未受精卵。寄生蜂的性别比例通常不高于1:1。寄生蜂的寄主是一块块地分布的，因此同一块地的后代之间的交配不是随机的。当交配在整个种群中不是随机的，就没有理由产生比使所有雌性受精所需的更多的儿子，所以理论上预期的性别比例是女性偏向的。此外，理论预测，即使性别比例偏向女性，性别比例的遗传变异也很小。尽管有理论预测，但在许多寄生蜂中已经证明了性别比例的遗传变异。猛禽Muscidifurax raptor是一种黄蜂，攻击各种苍蝇的蛹。它用于家禽农场和牛饲养场的家蝇和马厩的生物防治。研究人员将进行一系列实验，以描述性别比例的遗传变异和相关特征，如终生繁殖力、寿命和后代存活率。还将研究维持性别比例遗传变异的机制。这项研究在生物防治方面也有应用，因为它将指出人工选择性别比例将如何影响其他性状，并决定是否在所有环境中都能平等地表达有利性状。

In most species, the numbers of sons and daughters are equal, and this 1:1 sex ratio is found generally in animals with large, randomly mating populations. Even sex ratios are a consequence of chromosomal sex determination (e.g. mammals, in which females are XX and males are XY). In animals with this kind of sex determination, there is little or no genetic variation for sex ratio. In Hymenoptera (bees, ants and wasps), however, sex is not determined in this way; female offspring arise from fertilized eggs, and males arise from unfertilized eggs. Sex ratios that regularly differ from 1:1 are found in parasitic wasps. The hosts of parasitic wasps are distributed in patches, so mating among the offspring from a patch is not random. When mating is not random throughout a population, there is no reason to produce more sons than are necessary to inseminate all the females, so the theoretically expected sex ratio is female-biased. Furthermore, theory predicts that there will be little genetic variation in sex ratio even when sex ratio is female-biased. Despite theoretical predictions, genetic variation in sex ratio has been demonstrated in a number of parasitic wasps. Muscidifurax raptor is a wasp that attacks the pupae of various fly species. It is used for biological control of houseflies and stableflies at poultry farms and cattle feedlots. The investigators will conduct a series of experiments that will describe the genetic variation in sex ratio and related characters like lifetime fecundity, longevity, and survival of offspring. Mechanisms that could maintain genetic variation for sex ratio will also be examined. This research also has applications for biological control because it will point out how artificial selection for sex ratio will affect other traits, and determine whether favored traits are expressed equally in all environments.