DOI: 10.5061/dryad.cfxpnvxfx
title: Data from: Potential drivers and implications of a balanced breeding sex ratio in a small population of an imperiled species with environmental sex determination

description: Small populations of imperiled species are susceptible to the negative
 consequences of skewed sex ratios. In imperiled species with environmental
 sex determination such as sea turtles, examining sex ratios across a range
 of environments and population abundance levels can provide insight into
 factors that influence population resilience, which can then be the foci
 of management plans for these species. Breeding sex ratios (the ratio of
 actively breeding males to females during a reproductive season; BSRs)
 extrapolated from genetic parentage analyses are a common approach for
 enumerating sex ratios in sea turtles. Such analyses also allow for the
 characterization of multiple paternity within sea turtle clutches, which
 should reflect BSRs and breeding behaviors. We characterized the first BSR
 for a breeding assemblage of loggerhead sea turtles (Caretta caretta)
 belonging to the temperate, low-abundance Northern Gulf of Mexico Recovery
 Unit using genotypes of 16 microsatellite loci from nesting females and
 hatchlings. Unlike prior studies at both more-tropical and more-temperate,
 and higher-abundance, Recovery Units in this region, we found a balanced
 BSR of 1.3:1 males: female and a low incidence (~17%) of multiple
 paternity. This suggests that there are relatively few males breeding at
 this assemblage and within this Recovery Unit. Beaches in this region are
 expected to produce substantial numbers of male hatchlings based on sand
 temperature data. The relative dearth of mature males may then be due to
 hydrologic disturbances that disproportionately affect the fitness and
 survival of male hatchlings, or due to demographic stochasticity. More
 work is needed to study the factors that might influence male hatchling
 production and fitness in this region, particularly as climate change is
 predicted to lead to feminization in global sea turtle populations. Our
 work demonstrates the broad utility of characterizing BSRs and other sex
 ratios across a range of populations in imperiled, environmentally
 sensitive species.
description: # Potential drivers and implications of a balanced breeding sex ratio in a
 small population of an imperiled species with environmental sex
 determination
 [https://doi.org/10.5061/dryad.cfxpnvxfx](https://doi.org/10.5061/dryad.cfxpnvxfx) These data include: microsatellite genotypes across 16 loci for hatchling and female loggerhead sea turtles (*Caretta caretta*) sampled on St. George Island, Florida (SGI_loggerhead_genos_2022.csv); the output of COLONY 2.0 run using these microsatellite data (Colony_Output.csv); and an R markdown script used to analyze and visualize the COLONY output (SGI_BSR_Analyses.Rmd). ## Description of the data and file structure Microsatellite genotype file (SGI_loggerhead_genos_2022.csv) includes one column for individual ID (*individual_id*), one column to identify whether the individual is a hatchling or a female (*lifestage*), and 32 columns for microsatellite alleles (two columns for each locus). Each locus (column header) is followed by "A" or "B" to distinguish the two alleles. Alleles are presented as basepair counts. "*" indicates loci/alleles that did not amplify or could not be called with confidence.  COLONY output file (Colony_Output.csv) includes one column with the COLONY cluster index (*ClusterIndex*; an aid to identifying family groups), one column with the probability of each parentage assignments (*Probability*), and three columns with hatchling (*Offspring*), inferred paternal (*Father*), and inferred maternal (*Mother*) ID's. "*" before the inferred paternal ID indicates unsampled fathers inferred by COLONY (in this case, all fathers). "#" before the inferred maternal ID indicates unsampled mothers inferred by COLONY. R markdown script (SGI_BSR_Analyses.Rmd) includes all resources (package loading, R scripts) to import and analyze COLONY outputs and to generate figures used in the publication.  ## Sharing/Access information Links to other publicly accessible locations of the data: * [https://github.com/isilverg/BSR_Analyses](https://github.com/isilverg/BSR_Analyses) * [https://github.com/FuentesLab/BSR_Analyses](https://github.com/FuentesLab/BSR_Analyses) ## Code/Software R markdown script (SGI_BSR_Analyses.Rmd) can be open, edited, and run in Rstudio.