DOI: 10.5061/dryad.gj495j2
title: Male genital lobe morphology affects the chance to copulate in Drosophila pachea

description: Abstract Introduction Male genitalia are thought to ensure transfer of
 sperm through direct physical contact with female during copulation.
 However, little attention has been given to their pre-copulatory role with
 respect to sexual selection and sexual conflict. Males of the fruitfly
 Drosophila pachea have a pair of asymmetric external genital lobes, which
 are primary sexual structures and stabilize the copulatory complex of
 female and male genitalia. We wondered if genital lobes in D. pachea may
 have a role before or at the onset of copulation, before genitalia
 contacts are made. Results We tested this hypothesis with a D. pachea
 stock where males have variable lobe lengths. In 92 mate competition
 trials with a single female and two males, females preferentially engaged
 into a first copulation with males that had a longer left lobe and that
 displayed increased courtship vigor. In 53 additional trials with both
 males having partially amputated left lobes of different lengths, we
 observed a weaker and non-significant effect of left lobe length on
 copulation success. Courtship durations significantly increased with
 female age and when two males courted the female simultaneously, compared
 to trials with only one courting male. In addition, lobe length did not
 affect sperm transfer once copulation was established. Conclusion Left
 lobe length affects the chance of a male to engage into copulation. The
 morphology of this primary sexual trait may affect reproductive success by
 mediating courtship signals or by facilitating the establishment of
 genital contacts at the onset of copulation.
description: <strong>Genitalia preparations <em>D.
 pachea</em>, stocks</strong><br>Images for genital lobe
 length measurements <em>D. pachea</em> lab-stocks
 15090-1698.01, 15090-1698.02, and selection stock. md5sum:
 f75b342d0bb56d1c3b31cfbc355c64c5
 supplementary-data_1_epandrium-preparations_stocks.tar.gz
 <strong>Female spermathecae, mate-competition
 experiment</strong><br>Images for male genital lobe length
 measurements (<em>D. pachea</em> selection stock). md5sum:
 c82caf1bdf51900b41e3dbd5fb17fe7a 
 supplementary-data_2_spermathecae-preparations_mate-competition.tar.gz <strong>Male genitalia, mate-competition experiment</strong><br>Images for male genital lobe length measurements (<em>D. pachea</em> selection stock). md5sum: 04691905ff8e611eaade77c2cf8eba9e  supplementary-data_2_epandrium-preparations_mate-competition.tar.gz <strong>Left anterior legs, mate-competition experiment</strong><br>Images for male genital lobe length measurements (<em>D. pachea</em> selection stock). md5sum: 29fb466684df4b5df816d36285bc9c0c  supplementary-data_2_leg-preparations_mate-competition.tar.gz <strong>Movies, mate-competition experiment, females 1698.01</strong><br>Movies for mating behavior analysis of <em>D. pachea</em> females of stock 15090-1698.01 and two males of the selection stock. md5sum: 43e5215b5add2004d154c22afb35826f  supplementary-data_3_movies_1698-01_sel-lobe-length.tar.gz <strong>Movies, mate-competition experiment, females 1698.02</strong><br>Movies for mating behavior analysis of <em>D. pachea</em> females of stock 15090-1698.02 and two males of the selection stock. md5sum: 9da8fc9689256f9803ccacace1c0f3e0  supplementary-data_3_movies_1698-02_sel-lobe-length.tar.gz <strong>Movies, mate-competition experiment, females 1698.01, lobe surgery</strong><br>Movies for mating behavior analysis of <em>D. pachea</em> females of stock 15090-1698.01 and two males of the selection stock with surgically modified lobes. md5sum: 5f69e30f4e487ef17242d9f7bca6be5a  supplementary-data_3_movies_1698-01_modif-lobe-length.tar.gz <strong>PacData,</strong> dataset for mate-competition analysis using the R-package TerryBradley2