The less explored impacts of Sexual Selection: Male mate-choice on female fitness traits and functional senescence of the sexes in Drosophila
Store, S
Date: 10 June 2019
Publisher
University of Exeter
Degree Title
Masters by Research in Biological Sciences
Abstract
Sexual selection is largely responsible for widespread sexual dimorphism. This includes extreme condition-dependent phenotypes that often characterise males, enhancing their sexual fitness because females prefer males with exaggerated traits. Females tend to be drabber and less frequently display their reproductive quality. While there ...
Sexual selection is largely responsible for widespread sexual dimorphism. This includes extreme condition-dependent phenotypes that often characterise males, enhancing their sexual fitness because females prefer males with exaggerated traits. Females tend to be drabber and less frequently display their reproductive quality. While there are a number of classical explanations for this general pattern, it has only recently been suggested that sexual conflict could also be important, with females avoiding bright pigmentation and markers of their quality to avoid the costs of male sexual harassment but this idea has not been subjected to much testing. In addition to effects on sexual behaviours and morphology, sexual selection can also affect life-history strategies and in particular, aging. Aging, declines in fertility and increases in mortality with age, is widespread and sex differences in fertility declines and mortality increases with age are common, largely resulting from sexual selection. Much less is known about possible sex differences in functional senescence (i.e. how much and how quickly different traits lose function over age) and the role of sexual selection in causing different patterns of functional senescence. This thesis used insect models to investigate why sexual selection may not favour female signals of quality (Chapter 1) and whether the sexes differed in performance declines with age (Chapter 2). I first tested if male harassment of high quality females reduces female fitness and found no male preference or increased harassment directed towards high-quality females in Drosophila simulans. I found that long-term harassment reduces lifespan but overall increases fecundity. However, short-term harassment decreases fecundity early in life. When exploring the role of sexual selection in driving diverse patterns of functional senescence, I found that the sexes broadly age in similar patterns and for the most part follow similar patterns of functional decline as they age. Although the patterns in aging are similar, I find that traits lose function at different rates which is contrary to traditional aging theory of functional senescence. Jointly, this thesis highlights the different affects of sexual selection across taxa and how this is true even in closely related species like D. simulans and D. melanogaster. Results are discussed in relation to sexual selection and aging theory.
MbyRes Dissertations
Doctoral College
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