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

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Abstract

When females mate with more than one male, sexual selection acts both before and after mating. The interaction between pre- and postmating episodes of selection is expected to be context dependent, but few studies have investigated how total sexual selection changes under different ecological conditions. We examined how population density mediates the interaction between pre- and postmating sexual selection by establishing replicate populations of the horned dung beetle Onthophagus taurus at low, medium, and high densities, and then using microsatellite-based parentage analyses to measure male fitness. We found that mating success and fertilization success were positively correlated at all three densities, but the strength of the correlation decreased with increasing density. We also found a shift from negative to positive linear selection on testes mass as density increased, and opposing selection on weapons and testes at high densities. These patterns suggest that the importance of postmating processes increases with increasing population density, which reduces the selective advantage of weapons for premating contest competition, and increases the selective advantage of large ejaculates for postmating sperm competition. We expect that density-dependent selection on testes mass has contributed to the phenotypic variation observed between natural populations of O. taurus that differ in density.

LanguageEnglish
Pages893-905
Number of pages13
JournalEvolution
Volume72
Issue number4
DOIs
StatePublished - 1 Apr 2018

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Population Density
sexual selection
Testis
population density
Weapons
Onthophagus taurus
Beetles
testes
Fertilization
Microsatellite Repeats
weapon
Population
Spermatozoa
contest competition
sperm competition
dung beetles
parentage
mating success
fertilization (reproduction)
phenotypic variation

Cite this

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abstract = "When females mate with more than one male, sexual selection acts both before and after mating. The interaction between pre- and postmating episodes of selection is expected to be context dependent, but few studies have investigated how total sexual selection changes under different ecological conditions. We examined how population density mediates the interaction between pre- and postmating sexual selection by establishing replicate populations of the horned dung beetle Onthophagus taurus at low, medium, and high densities, and then using microsatellite-based parentage analyses to measure male fitness. We found that mating success and fertilization success were positively correlated at all three densities, but the strength of the correlation decreased with increasing density. We also found a shift from negative to positive linear selection on testes mass as density increased, and opposing selection on weapons and testes at high densities. These patterns suggest that the importance of postmating processes increases with increasing population density, which reduces the selective advantage of weapons for premating contest competition, and increases the selective advantage of large ejaculates for postmating sperm competition. We expect that density-dependent selection on testes mass has contributed to the phenotypic variation observed between natural populations of O. taurus that differ in density.",
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Population density mediates the interaction between pre- and postmating sexual selection. / McCullough, E.L.; Buzatto, B.A.; Simmons, L.W.

In: Evolution, Vol. 72, No. 4, 01.04.2018, p. 893-905.

Research output: Contribution to journalArticle

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