Bateman in Nature: Predation on Offspring Reduces the Potential for Sexual Selection

Abstract

Sexual Versus Natural Selection In a 1948 experiment with Drosophila , Angus Bateman showed that sexual selection is strongest in males (versus females) because the number of mates they obtain is correlated with the number of offspring they produce. This relationship between mate number and offspring number has since become known as the Bateman slope, but there has been much debate concerning whether such a relationship can be expected in nature. Using a 30-year data set collected from a closed population of pronghorn antelope in Montana, Byers and Dunn (p. 802 ; see the Perspective by Wade ) show that the relationship between mate number and offspring number indeed provides an opportunity for strong sexual selection in this polygynous and dimorphic species—however, environmental effects can make such selection null. In years when coyote predation on newborn fawns was high, sexual selection could not operate and reproductive success was instead determined by natural selection.