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Supporting Information
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Genetic structure methods
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We used the program Structure v.2.3.3 (Pritchard et al. 2000) to investigate possible
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genetic differentiation among females and inferred males breeding at our study site. We used
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genotypes at 13 loci from 87 adult female turtles that nested at the site between 2007 and
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2010 and 87 male genotypes that were inferred using reconstructed single-locus paternal
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genotypes from the Colony (Wang 2004, Wang & Santure 2009) analysis. Colony only
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reconstructs parental genotypes on a single locus basis and makes no attempt to infer
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multilocus parental genotypes. Inferring multilocus genotypes from single locus genotypes is
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difficult to do accurately because, with increasing numbers of loci, it quickly becomes highly
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likely that the inferred multilocus genotype is incorrect at at least one locus (Colony user
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guide, version 2.0). We only used single locus genotypes that were inferred with a probability
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of >0.75 and only included inferred males with genotypes reconstructed at a minimum of 10
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loci. Nonetheless, we urge that the results of the Structure analysis are considered
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conservative. We ran the analysis assuming a K (the number of potential distinct genetic
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clusters) of 1 to 5, with an admixture model, correlated allele frequencies and no prior
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location information. We conducted five iterations for each K with a run length of 200 000
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iterations after a burn-in of 100 000 iterations.
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Genetic structure results
Results of the Structure analyses suggest that there is no genetic differentiation within
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the female and inferred male turtles breeding at our study site. The mean log-likelihood was
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highest when assuming one cluster (K = 1), compared to values assuming a K of 2–5 (fig S1).
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Furthermore, when assuming a K of 2-5 all individuals in the sample were highly admixed
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and none were strongly assigned to one cluster or another, suggesting a single population.
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Figure S1
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Figure S1
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Output from a Structure analysis of 87 adult female turtles that nested at the study site
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from 2007 - 2010 and 87 inferred male genotypes based on reconstructed single-locus
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paternal genotypes from a Colony analysis. We ran five iterations of the analysis for each
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value of ‘K’ (the number of clusters) to determine the likelihood that the genetic structure of
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the data is explained by ‘K’ clusters.
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