DOI: 10.5061/dryad.vt4b8gv20
title: Adult sex-ratio bias does not lead to detectable adaptive offspring sex allocation via nest-site choice in a turtle with temperature-dependent sex determination

description: Sex-ratio theory predicts that parents can optimize their fitness by
 producing offspring of the rarer sex, yet there is a dearth of empirical
 evidence for adaptive sex allocation in response to the adult sex ratio
 (ASR). This is concerning, as anthropogenic disruption of the sex ratios
 of reproductive individuals threatens to cause demographic collapse in
 animal populations. Species with environmental sex determination (ESD) are
 especially at risk, but may possess the capacity to adaptively influence
 offspring sex via control over the developmental environment. For example,
 reptiles with temperature-dependent sex determination (TSD) could
 conceivably choose nest sites with thermal characteristics that produce
 offspring of the rarer sex. To test this hypothesis, we seeded three
 secure outdoor ponds with different sex ratios (~ 3:1, 1:1, and 1:3) of
 adult painted turtles (Chrysemys picta), a reptile species with TSD. We
 then quantified nesting traits that could influence nest temperature, and
 thus offspring sex ratio, including nesting date, nest depth, and nest
 canopy cover. We found no directional relationship between the ASR
 treatments and any measured nest traits, and thus reject our hypothesis.
 Interestingly, increased maternal body size was associated with reduced
 nest canopy cover, and this trend was more pronounced in the biased ASR
 treatments. If adaptive sex allocation occurs in this system, it instead
 may manifest via maternal epigenetic predisposition of offspring sex or in
 response to a phenomenon other than the ASR.
description: # Adult sex-ratio bias does not lead to detectable adaptive offspring sex
 allocation via nest-site choice in a turtle with temperature-dependent sex
 determination
 [https://doi.org/10.5061/dryad.vt4b8gv20](https://doi.org/10.5061/dryad.vt4b8gv20) ## Description of the data and file structure Data and code required to reproduce the analyses in "Adult sex-ratio bias does not lead to detectable adaptive offspring sex allocation via nest-site choice in a turtle with temperature-dependent sex determination" Data was collected to compare the nesting behaviour (timing, depth, and shade cover) of painted turtles (*Chrysemys picta*) in three outdoor enclosures with experimentally manipulated adult sex ratios (ASR). The purpose of the experiment was to ascertain whether species with temperature-dependent sex determination (TSD, incubation temperature determines the sex of embryos) could adaptively manipulate offspring sex via nest-site choice in response to the ASR. ### Files and variables #### File: ASR\_Data\_Crowther\_2023.csv **Description:** csv file containing nest characteristics for all the nests laid in the experimental enclosures. Missing values are indicated by "NA" (not available). ##### Variables * Date: The date that the nest was laid, format: M/DD/YYYY. * Jdate: The day of the year that the nest was laid (e.g. Jdate 152 = the 31st of May). * Pond: The letter identifier for the experimental pond that the nest was laid in. The adult sex ratio of the ponds varied, B = male-biased, C = equal sex ratio, and D = female-biased. * MomID: The unique identifier for the mother that laid the nest.  * SCL: The straight carapace (dorsal side of the shell) length of the mother in millimeters. * NestDepthCM: The depth of the nest in centimeters. * HemiPhoto: The file name of the hemispherical canopy cover photo. * SexRatio: The proportion male offspring in the clutch associated with the nest (hatchlings were incubated in a laboratory environment). NA values for this variable indicate that the data is not available because we did not determine the sex of hatchlings in those clutches. * Clutch.Size: The number of eggs in the clutch. * Clutch.no: The order the mother laid the clutch, 1 = mother's 1st clutch in season, 2 = mother's second clutch. * SW.Open: The percentage of sky area over the South West half of the nest not covered by vegetation or other shade. ### **File Folder: Nest Photos** **Description:** Hemispherical photographs of the sky area above nests, used to calculate nest canopy cover. The nests were photographed using a Nikon Coolpix S3600 camera equipped with a Zykkor fish eye lens (0.2x180°). The photographs are stored in a .jpeg format. Nest photographs are linked to the corresponding nest data by their file name, which is recorded in the 'HemiPhoto' column of ASR_Data_Crowther_2023.csv ## Code/software #### Nest\_trait\_analysis\_V3.R ##### Description: An R file containing code to repeat the analyses presented in '*Adult sex-ratio bias does not lead to detectable adaptive offspring sex allocation via nest-site choice in a turtle with temperature-dependent sex determination*' a manuscript submitted to Ecology and Evolution. The script also contains code for publication and supplementary graphs. The script requires the data file 'ASR_Data_Crowther_2023.csv' to perform the analyses. Code was compiled in R version 4.3.2 and uses the following packages: 'tidyverse', 'showtext', 'DHARMa', 'patchwork', 'lme4', 'glmmTMB', and 'emmeans'.