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Within-population sperm competition intensity does not predict asymmetry in conpopulation sperm precedence


Garlovsky, Martin et al. (2020), Within-population sperm competition intensity does not predict asymmetry in conpopulation sperm precedence, Dryad, Dataset,


Postcopulatory sexual selection can generate evolutionary arms races between the sexes resulting in the rapid coevolution of reproductive phenotypes. As traits affecting fertilization success diverge between populations, postmating prezygotic (PMPZ) barriers to gene flow may evolve. Conspecific sperm precedence is a form of PMPZ isolation thought to evolve early during speciation yet has mostly been studied between species. Here , we show conpopulation sperm precedence (CpSP) between Drosophila montana populations. Using Pool-seq genomic data we estimate divergence times and ask whether PMPZ isolation evolved in the face of gene flow. We find models incorporating gene flow fit the data best indicating populations experienced considerable gene flow during divergence. We find CpSP is asymmetric and mirrors asymmetry in non-competitive PMPZ isolation, suggesting these phenomena have a shared mechanism. However, we show asymmetry is unrelated to the strength of postcopulatory sexual selection acting within populations. We tested whether overlapping foreign and coevolved ejaculates within the female reproductive tract altered fertilization success but found no effect. Our results show that neither time since divergence nor sperm competitiveness predicts the strength of PMPZ isolation. We suggest that instead cryptic female choice or mutation-order divergence may drive divergence of postcopulatory phenotypes resulting in PMPZ isolation. This article is part of the theme issue ‘Fifty years of sperm competition’.

Usage Notes

Data file consists of a single zipped folder containing four .csv files (described below) and R scripts to perform statistical analyses for each section described in the paper. All can be run from the R project included. Demographic modelling was performed using data available from: Parker et al. (2018). "Inter- and intra-specific genomic divergence in Drosophila montana shows evidence for cold adaptation":

Variable definitions:


$BLOCK     : experimental block
$cross_1   : first mating female population x male population
$cross_type: second mating female population x male 1 population x male 2 population
$female    : female population (Colorado or Vancouver)
$Mating    : first or second mating
$RADS      : irradiation treatment; first male (M1), second male (M2), both males (DOUBLE), or neither (CONTROL)
$eggs      : number of eggs laid
$hatch     : number of eggs laid that hatched
$unhatched : eggs - hatch


$population: population (Colorado or Vancouver)
$sex       : male or female
$soma_wt   : dry carcass mass - reproductive tract
$rt_wt     : dry reproductive tract mass
$bd_wt     : soma_wt + rt_wt


$Male_ID: Unique male ID
$Mating : Mating number
$POP    : Population (Colorado or Vancouver)
$count  : Progeny count



Natural Environment Research Council, Award: NE/L002450/1

University of St Andrews