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Related Experiment Video

Updated: Feb 14, 2026

Assessment of Sexual Behavior of Male Mice

Assessment of Sexual Behavior of Male Mice

Published on: March 5, 2020

Population density mediates the interaction between pre- and postmating sexual selection.

Erin L McCullough¹, Bruno A Buzatto¹, Leigh W Simmons¹

¹Centre for Evolutionary Biology, School of Biological Sciences (M092), The University of Western Australia, Crawley, Western Australia 6009, Australia.

Evolution; International Journal of Organic Evolution

|February 19, 2018

Summary

This summary is machine-generated.

Population density impacts sexual selection in dung beetles. Higher densities increase the importance of postmating selection, favoring larger testes over weapons for male reproductive success.

Keywords:

Dung beetle Onthophagus multivariate selection sexual selection sperm competition variance decomposition

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Area of Science:

Evolutionary Biology
Sexual Selection
Behavioral Ecology

Background:

Sexual selection operates through pre- and postmating processes when females mate multiply.
The interplay between pre- and postmating sexual selection is context-dependent, influenced by ecological factors.
Few studies have explored how ecological conditions modulate the combined effects of pre- and postmating sexual selection.

Purpose of the Study:

To investigate how population density mediates the interaction between pre- and postmating sexual selection.
To understand the impact of varying population densities on male fitness in Onthophagus taurus.

Main Methods:

Established replicate populations of the horned dung beetle (Onthophagus taurus) at low, medium, and high densities.
Utilized microsatellite-based parentage analyses to quantify male fitness.
Measured mating success, fertilization success, and correlated these with male traits like testes mass and weapons.

Main Results:

Mating and fertilization success were positively correlated across all densities, but this correlation weakened with increasing density.
Selection shifted from negative to positive on testes mass as density increased.
Opposing selection pressures on weapons and testes were observed at high population densities.

Conclusions:

Increasing population density enhances the relative importance of postmating sexual selection.
High densities reduce the advantage of weapons for contest competition and increase the advantage of large ejaculates for sperm competition.
Density-dependent selection on testes mass likely contributes to observed phenotypic variation in natural Onthophagus taurus populations.