DOI: 10.5061/dryad.98sf7m0k9
title: Long-term resilience of primary sex ratios in a species with temperature dependent sex determination after decades of climate warming

description: Species with environmental sex determination (ESD) have persisted through
 deep time, despite massive environmental perturbation in the geological
 record. Understanding how species with temperature-dependent sex
 determination (TSD), a type of ESD, persist through climate change is
 particularly timely given the current climate crisis, as highly biased sex
 ratios and extinction are predicted. Since 1982, we have studied primary
 sex ratios of a reptile with TSD (Chelydra serpentina). Primary sex ratios
 remained unchanged over time, despite warming in the environment.
 Resilience of the primary sex ratio occurred via a portfolio effect,
 realized through remarkable intra-annual variation in nest-level sex
 ratios, leading to a relatively consistent mean annual sex ratio.
 Intra-annual variation in nest-level sex ratios was related to variation
 in egg burial depth coupled with large clutch sizes, creating thermal
 gradients in the nest, and promoting mixed-sex clutches. Further, both
 locally and globally, sustained increases in nighttime air temperature
 contribute more to warming than increases in daily maximum temperature,
 but development rate was affected more strongly by maximum daily air
 temperature, conferring additional resilience to overall warming. Our
 study suggests that some TSD species may be resilient to warming and
 provides an example of how ESD may persist under environmental change.
description: Data file description: Nest Temperatures:
 Hourly nest temperature records from nests that were laid on the dam or
 translocated there shortly after laying. Missing values indicate
 temperature logger failure. There is a file for each year between 1985 and
 1998. Within each of these files: DATE - indicates the
 date that the nest temperature was measured on. Each date appears in this
 column 24 times as nest temperatures were measured hourly. 
 The following coloumns are nest temperatures - the names of the
 column indicate the turtle ID of the female that laid the nest. 
 AirTemp: These are daily air temperature records downloaded from
 https://climate.weather.gc.ca/historical_data. They span January 1st
 1965-October 20th 2020 Date - the date in format
 d/m/y Year - year of measurement extracted from Date
 column Day - day of the month extracted from Date
 column Max.Temp - daily maximum temperature measured at
 the weather station Min.Temp - daily minimum
 temperature measured at the weather station Mean.Temp -
 daily mean temperature measured at the weather station
 SexRatio: contains nest dates, and sex ratios (where applicable -
 NAs where nest sex ratio was not measured) for all nests laid naturally on
 the Sas Dam between 1973 and 2020. Individual - the
 unique individual identifier of nesting females (1-124)
 Year - the year that the nest was laid in
 NestDate - the date that the nest was laid in Y-m-d
 format n.female - the number female hatchlings that
 emerged from the eggs of that clutch that were taken to the
 laboratory n.male - the number male hatchlings that
 emerged from the eggs of that clutch that were taken to the
 laboratory ClutchSize - the total number of eggs laid
 in that nest. n.female + n.male does not necessarily equal clutch size
 because often only a subset of eggs were taken to be sexed.
 EggDepth: This contains egg depth measures from 2018, along with
 maternal ID, egg number, and sex Maternal ID - the
 unique individual identifier of nesting females (1-5). Female 1 in this
 dataset is not the same as Individual 1 in the Clutch Data.
 EggNumber - the position of the egg within the clutch. As
 researchers excavate the nest after laying eggs are given a number based
 on the order that they are removed (1st removed = last laid = egg number
 1, last removed = first laid egg = egg number n). Depth
 - the depth of the egg from the substrate surface in
 centimeters. Sex - the sex of the embryo that hatched
 from the egg SexEmb - a numeric version of the previous
 column (0 = female, 1 = male). EggOrder: This contains
 the sex of hatchlings, their egg number, maternal ID, and year. This is
 for nests laid naturally on the dam between 1983 and 1997. 
 Maternal ID - the unique individual identifier of nesting females
 (1-53). Female 1 in this dataset is not the same as Female 1 in the Egg
 Depth Data or Individual 1 in the Clutch Data. Year -
 the year the nest was laid in EggNo - the position of
 the egg within the clutch. As researchers excavate the nest after laying
 eggs are given a number based on the order that they are removed (1st
 removed = last laid = egg number 1, last removed = first laid egg = egg
 number n). Clutch ID - indicated eggs that came from
 the same clutch (1-195).  Sex - the sex of the embryo
 that hatched from the egg SexEmb - a numeric version of
 the previous column (0 = female, 1 = male). NestDepth:
 This contains the measures of depth of top and bottom of nest cavity for
 31 nests laid on the dam or alternate sites in 2020. Maternal ID and nest
 site (dam/alt) are included. maternalID - the unique
 individual identifier of nesting females (1-53). Female 1 in this dataset
 is not the same as Female 1 in the Egg Depth/Order Data or Individual 1 in
 the Clutch Data. MaxDepth - the depth of the bottom of
 the nest chamber from the substrate surface (0cm).
 TopNest - the depth of the top of the nest chamber from the
 substrate surface (0cm). orig.site - the location of
 the nest site (dam/ALT). dam = Lake Sasajewun dam, alt = alternate site
 but from the same watershed.  Staging: This contains
 data on ED20 stage of eggs laid naturally on the dam between 1983 and
 1995. ED20 stage is the average stage of all eggs collected on the
 specified date. Maternal ID is also included. Year -
 the year the nest was laid Individual - the maternal ID
 of the turtle that laid the nest Date.Collected - the
 date that the egg was removed from the nest for staging. Eggs were either
 staged immediately or frozen immediated after collection
 ED20.Stage - the stage of the embryo in equivalent development at
 20 degrees. R-file description:
 Scripts must be run in the order displayed here as each builds on
 the previous. I also assume here that all data and script files are
 downloaded within a single project. 1) development1:
 Script for determining daily within nest development from nest
 temperatures and Schoolfield model (Appendix 1) 2)
 development2: Regression of within nest air temperature on daily
 development (Appendix 1) 3) validation: Regressing
 predicted egg stage from our model on measured egg stage data &
 applying Rollinson et al 2018 correction. 4)
 mainanalyses: All regressions in main text and appendix 2
 5) figures: All figures from main text and appendix