The adaptive value of male-biased sex ratios in stressed animals
University of Chicago Press
The question of adaptive sex ratio manipulation in higher vertebrates remains a controversial issue. Trivers and Willard (1973) proposed that facultative adjustment of the sex ratio could be adaptive when the mother can produce an excess of the more profitable sex. They emphasized that "natural selection should favor parental ability to adjust the sex ratio of their offspring according to their ability to invest" (p. 90). Generally, it has been assumed that strong mothers invest more per offspring, and should preferentially produce males in species with polygynous or promiscuous mating systems. Conversely, it has been assumed that weak females invest less per offspring, and should therefore bias their offspring sex ratio toward females.
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McGinley, M. A. (1984). The adaptive value of male-biased sex ratios in stressed animals. American Naturalist, 124(4), 597-599. Retrieved from http://www.jstor.org/stable/2461600