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As a young woman, Dorinda submits passively to the expectations of Calvinist belief and Darwinian sexual selection; as a result, she stumbles just as passively into pregnancy and is almost ruined by motherhood.
Here I explore the role of gnathopod characteristics in male reproductive success by measuring aspects of sexual selection (pairing success) and natural selection (success in mating with larger, more fecund females) on gnathopod size in the two amphipod ecotypes.
However, aside from sexual selection, three further factors may lead to the evolution of sexual dimorphism: (i) fecundity selection, which favours larger bodies in females providing more space for eggs; (ii) competition between sexes, which should lead to sexual dimorphism in body size or food consumption structures (Selander 1972); and (iii) mating performance through intrasexual competition, which favours morphological structures maximizing the number of successful mating attempts (Gvozdik & Van Damme 2003).
Although sexual selection was originally conceived to explain traits that appeared to reduce survival, it also has the potential to accelerate adaptation.
Key words: Sexual selection, Brain size, Reproductive investment, Trade-off hypothesis
In this study we examine two clines in a morphological character--the shape of the male genitalia--and we compare cline shape between transects to examine the role sexual selection might play in the evolution of this character and in reproductively isolating the grasshopper subspecies, Barytettix humphreysii humphreysii and B.
This adds evidence to the claim that the bristles are used for a reproductive function, and may suggest that sexual selection is involved.
However, it is important to emphasize that the causes, ecological or selective sexual, of sexual dimorphism do not need to be exclusive: sexual differences might evolve primarily due to sexual selection and subsequently be fixed by natural selection if the opposite sex shows differences in the use of ecological resources (Power, 1980).
Abstract--Parental care, sexual selection, and life history are major areas of research in evolutionary ecology.
"Disruption of ecosystems to study sexual selection seems a bit extreme." John Day offered a suggestion for a new study: "What say we introduce hungry tigers into the authors' lab to see if it reduces their swaggering, head-bobbing behavior?"
The study by scientists at the University of Exeter and the Universities of Okayama and Tsukuba in Japan investigated the complicated sexual conflict over mating in Gnatocerus cornutus, the horned flour-beetle and found that female mate choice and male-male competition are the typical mechanisms of sexual selection, which do not do not always favour the same males.