DOI: 10.5061/dryad.v41ns1rs9
title: Data from: Shifts in reproductive investment in response to competitors lowers male reproductive success

description: In many species, males exhibit phenotypic plasticity in sexually selected
 traits when exposed to social cues about the intensity of sexual
 competition. To date, however, few studies have tested how this plasticity
 affects male reproductive success. We initially tested whether male
 mosquitofish, Gambusia holbrooki (Poeciliidae), change their investment in
 traits under pre- and post- copulatory sexual selection depending on the
 social environment. Focal males were exposed, for a full spermatogenesis
 cycle, to visual and chemical cues of rivals that were either present
 (competitive treatment) or absent (control). Males from the competitive
 treatment had significantly slower swimming sperm, but did not differ in
 sperm count from control males. When two males competed for a female,
 competitive treatment males also made significantly fewer copulation
 attempts and courtship displays than control males. Further, paternity
 analysis of 708 offspring from 148 potential sires, testing whether these
 changes in reproductive traits affected male reproductive success, showed
 that males previously exposed to cues about the presence of rivals sired
 significantly fewer offspring when competing with a control male. We
 discuss several possible explanations for these unusual findings.
description:   We used the eastern mosquitofish,
 <i>Gambusia holbrooki</i>, to<i> </i>test whether
 exposure to social cues presumed to indicate the level of sexual
 competition affects male investment in different sexually selected traits,
 and ultimately reproductive success. We experimentally manipulated the
 perceived level of sexual competition by placing males in either a
 competitive or control environments for a full spermatogenesis cycle. More
 specifically, we provided test males with visual and olfactory access to a
 female, who was either alone or housed with rival males. We then
 investigated whether this affected male behavior and/or sperm production.
 Crucially, we then tested for an effect of the social treatment on male
 reproductive success when males from each treatment competed one on one
 with each other to sire offspring.  Males were exposed to the social
 treatments for five weeks and were then stripped of sperm to quantify
 sperm number and velocity. To restore their sperm reserves, males were
 returned to their treatment aquarium for another week. Next, we placed a
 pair of size-matched males from the competitive and control treatment with
 a virgin female and recorded their mating behavior on the first and third
 day. After one week, females were transferred to separate aquaria to give
 birth and we recorded the total amount of offspring produced. For a
 proportion of the offspring we performed paternity analysis to calculate
 male reproductive success. Finally, we also photographed and measured
 males and females.  For more information see
 publication Spagopoulou et al. AmNat 2020.
description: Spagopoulou-etal_AmNat2020.csv contains the dataset used in this
 publication  Spagopoulou-etal_AmNat2020-ReadMe.txt
 contains the explanation of the columns of the csv file
 Spagopoulou-etal_AmNat2020.R contains the R script with the
 analysis and model selection