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Sexual selection: Harem size and the variance in male reproductive success

Wade, Michael J. and Shuster, Stephen M. (2004) Sexual selection: Harem size and the variance in male reproductive success. American Naturalist, 164 (4). E83-E89. ISSN 1537-5323

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Publisher’s or external URL: http://dx.doi.org/10.1086/424531

Abstract

Sexual selection is potentially stronger than natural selection when the variance in male reproductive fitness exceeds all other components of fitness variance combined. However, measuring the variance in male reproductive fitness is difficult when nonmating males are absent, inconspicuous, or otherwise difficult to find. Omitting the nonmating males inflates estimates of average male reproductive success and diminishes the variance, leading to underestimates of the potential strength of sexual selection. We show that, in theory, the proportion of the total variance in male fitness owing to sexual selection is approximately equal to H, the mean harem size, as long as H is large and females are randomly distributed across mating males (i.e., V-harem = H). In this case, mean harem size not only provides an easy way to estimate the potential strength of sexual selection but also equals the opportunity for sexual selection, I-mates. In nature, however, females may be overdispersed with V-harem <H or more aggregated than random with V-harem >H. We show that H+ (k-1) is a good measure of the opportunity for sexual selection, where k is the ratio V-harem/H. A review of mating system data reveals that in nature the median ratio for V-harem/H is 1.04, but as H increases, females tend to become more aggregated across mating males with V-harem two to three times larger than H.

Item Type: Article
Publisher’s Statement: © 2004. Copyright by The University of Chicago Press for The American Society of Naturalists.
ID number or DOI: 10.1086/424531
Keywords: bat; dimorphism; Ecology; harem size; male mating success; male reproductive success; Polygyny; Population; ratio; reproductive competition; sex ratio; sexual selection; System
Subjects: Q Science > QL Zoology
Q Science > QP Physiology
NAU Depositing Author Academic Status: Faculty/Staff
Department/Unit: College of Engineering, Forestry, and Natural Science > Biological Sciences
Date Deposited: 30 Sep 2015 05:30
URI: http://openknowledge.nau.edu/id/eprint/320

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