DOI: 10.5061/dryad.ff94h
title: Data from: Sacrificial males: the potential role of copulation and predation in contributing to copepod sex-skewed ratios

description: Predation is thought to play a selective role in the emergence of
 behavioural traits in prey. Differences in behaviour between prey
 demographics may, therefore, be driven by predation with select components
 of the population being less vulnerable to predators. While under
 controlled conditions prey demography has been shown to have consequences
 for predation success, investigations linking these implications to
 natural prey population demographics are scarce. Here we assess
 predator-prey dynamics between notonectid predators (backswimmers) and
 Lovenula raynerae (Copepoda), key faunal groups in temperate ephemeral
 pond ecosystems. Using a combination of field and experimental approaches
 we test for the development and mechanism of predation-induced sex-skewed
 ratios. A natural population of L. raynerae was tracked over time in
 relation to their predator (notonectid) and prey (Cladocera) numbers. In
 the laboratory, L. raynerae sex ratios were also assessed over time but in
 the absence of predation pressure. Predation success and prey performance
 experiments evaluating differences between L. raynerae male, female,
 gravid female and copulating pairs exposed to notonectid predation were
 then examined. Under natural conditions, a female dominated copepod
 population developed over time and was correlated to predation pressure,
 while under predator-free conditions non sex-skewed prey population
 demographics persisted. Predator-prey laboratory trials showed no
 difference in vulnerability and escape performance for male, female and
 gravid female copepods, but pairs in copula were significantly more
 vulnerable to predation. This vulnerability was not shared by both sexes,
 with only female copepods ultimately escaping from successful predation on
 a mating pair. These results suggest that contact periods during copula
 may contribute to the development of sex-skewed copepod ratios over time
 in ecosystems dominated by hexapod predators. This is discussed within the
 context of vertebrate and invertebrate predation and how these dissimilar
 types of predation are likely to have acted as selective pressures for
 copepod mating systems.
description: Data_repository_fileThe study is comprised of a number of discrete components, each addressing specific hypotheses, as outlined in Table 1 of the associated Oikos manuscript. This data file is comprised of four data sheets. Data sheet 1 (Sex ratio-Field) contains percentage data for male and female Lovenula raynerae over the hydroperiod (Table 1- Field study). Data sheet 2 (Sex ratio-Lab) contains raw count data for male and female Lovenula raynerae, from a controlled laboratory experiment, over time (Table 1- Experiment 1). Data sheet 3 (Predation success experiment) contains raw count data from an experiment assessing predation success between the predator (Enithares sobria) and prey (Lovenula raynerae) (Table 1- Experiment 2). Data sheet 4 (Escape-Attack speed) contains maximum swimming speed data (expressed in mm per second) for Lovenula raynerae (prey) during escape events and for Enithares sobria (predator) during attack events (Table 1- Experiment 3).Data_repository_3_read_only.xlsx