Hilary Lee

Publication Date


Document Type


First Advisor

King, Bethia H.

Degree Name

B.S. (Bachelor of Science)

Legacy Department

Department of Biological Sciences


Natural selection is the process by which organisms accumulate favorable traits that increase reproductive success. One factor that may influence reproductive success is the ability to manipulate one's offspring sex ratio. Sex ratio manipulation has been especially well-examined in parasitoid wasps, in which manipulation may be quite common.The host-quality model proposes that females will lay a greater proportion of daughters on large hosts than on small hosts because the large host will provide greater resources for the daughters and subsequently will increase their fitness or their ability to pass on their genes by increasing their egg production (Charnov et al., 1981). The parasitoid wasp Muscidifurax raptor exhibits this sex ratio pattern (Seidl and King, in press). However, in M. raptor no evidence was found to support the model's assumption that sex ratio manipulation gives a female a selective advantage over females that do not manipulate their offspring (Seidl and King, in press). In response to Seidl and King, I attempt to offer an explanation for sex ratio manipulation in the absence of selection for the behavior. This study shows no detectable genetic variation in maternal sex ratio manipulation in response to host size in M. raptor. This suggests an alternative hypothesis to the host quality model—that offspring sex ratio manipulation persists only because there is a lack of genetic variation to do otherwise.


Includes bibliographical references.


9 pages




Northern Illinois University

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