9407965 ORZACK This is a study of two species of wasp, Nasonia giraulti and N. vitripennis. Females of these species, like those of many other Hymenoptera (ants, bees, and wasps), often produce more female than male offspring in their broods. One common explanation for such an excess (known as a female-biased sex ratio) is that it has evolved as a response to geographical subdivision of the population. However, there is no reliable information about population subdivision in these species (and many others like them). This study will provide such information. For both species, DNA sequences from individuals will be compared. The degree to which these sequences differ within and among localities will reveal whether these species have subdivided populations which will lead to the evolution of female-biased sex ratios. In addition, females will be compared to determine whether they differ in regard to the set of sex ratios they produce when producing offspring in the presence of varying numbers of other females. This study will also assess whether the number and kind of DNA sequence differences among individuals are accounted for by the theory that such differences are not affected by natural selection.
