MALE AND FEMALE REPRODUCTIVE ROLES IN THE CONTEXT OF LIFE HISTORY AND NUTRITIONAL ECOLOGY.
Abstract: Charles Darwin characterized sex roles as males pursuing and
competing to gain females attention, and females acting coy and choosy in selecting their
mates. Since then, the idea of "typical sex roles" has been a cornerstone for much of
sexual selection theory. However, the last forty years have seen numerous studies showing
that females in many species actively solicit multiple ... read morematings, and that males can be
prudent and even picky when choosing a mate. Understanding the causes and consequences of
these "non- typical" sex roles is an important part of contemporary biology. This
dissertation uses a framework that incorporates testing adaptive and non-adaptive
hypotheses to improve our knowledge of how non-typical male and female sexual traits and
behaviors evolve. The first part of this dissertation focuses on explaining sexual traits
and behaviors in Pieris rapae butterflies, a species whose mating system includes nuptial
gifts. My studies indicate that production of nuptial gifts by males, and acquisition of
nuptial gifts by females are important drivers of non-typical sexual traits and behaviors.
First, limitation of dietary nitrogen decreased female but not male allocation to primary
reproduction. Low-nitrogen males sacrificed wing coloration, a trait associated with their
mating success. P. rapae males might maximize fitness by protecting their investment in
nuptial gifts and carefully choosing a mate. Supporting this idea I showed that males
preferred to mate with more fecund females that had been reared in high-nitrogen diets. My
studies also indicated that male mate choice drives exaggeration of female coloration, a
trait that honestly signals female fecundity in P. rapae. Using an individual based
simulation and knowledge based on lepidopteran biology, I demonstrated that male gifts can
determine the magnitude of benefits that females obtain from allocating resources to
ornaments. These simulations showed that females obtained maximum benefit by allocating
almost half of their reproductive resources to ornaments and by acquiring multiple gifts.
In the last study presented in this dissertation, I used Tribolium castaneum flour beetles
and applied sexually antagonistic selection on body size, which is an important trait for
both male and female reproduction. My results showed that between-sex genetic correlations
constrained the independent evolution of body size. These results support the idea that
certain traits and behaviors, such as body size and ornamentation, can evolve as a
correlated response to selection on the other sex.
Thesis (Ph.D.)--Tufts University, 2013.
Submitted to the Dept. of Biology.
Advisor: Sara Lewis.
Committee: Frances Chew, Michael Reed, Colin Orians, Jan Pechenik, and Philip Starks.
Keywords: Evolution & development, Ecology, and Behavioral sciences.read less