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, 3 (14), 4736-47

Strong Male-Biased Operational Sex Ratio in a Breeding Population of Loggerhead Turtles (Caretta Caretta) Inferred by Paternal Genotype Reconstruction Analysis

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Strong Male-Biased Operational Sex Ratio in a Breeding Population of Loggerhead Turtles (Caretta Caretta) Inferred by Paternal Genotype Reconstruction Analysis

Jacob A Lasala et al. Ecol Evol.

Abstract

Characterization of a species mating systems is fundamental for understanding the natural history and evolution of that species. Polyandry can result in the multiple paternity of progeny arrays. The only previous study of the loggerhead turtle (Caretta caretta) in the USA showed that within the large peninsular Florida subpopulation, multiple paternity occurs in approximately 30% of clutches. Our study tested clutches from the smaller northern subpopulation for the presence of multiple paternal contributions. We examined mothers and up to 20 offspring from 19.5% of clutches laid across three nesting seasons (2008-2010) on the small nesting beach on Wassaw Island, Georgia, USA. We found that 75% of clutches sampled had multiple fathers with an average of 2.65 fathers per nest (1-7 fathers found). The average number of fathers per clutch varied among years and increased with female size. There was no relationship between number of fathers and hatching success. Finally, we found 195 individual paternal genotypes and determined that each male contributed to no more than a single clutch over the 3-year sampling period. Together these results suggest that the operational sex ratio is male-biased at this site.

Keywords: Caretta caretta; Northwest Atlantic Ocean; conservation genetics; microsatellites; paternal contributions; polyandry.

Figures

Figure 1
Figure 1
Loggerhead leaving the beach in the dawn on Wassaw Island, Georgia, USA.
Figure 2
Figure 2
Graph showing the relationship between the two programs used and the 3 years analyzed. (N2008 = 23, N2009 = 21, N2010 = 28). The gray bars are GERUD by year, the white bars are COLONY by year, G F/N represents the number of fathers per clutch according to GERUD, and C F/N represents the number of fathers per clutch according to COLONY
Figure 3
Figure 3
Average number of fathers by year using both estimator methods. There is a significant negative relationship between the number of fathers due to year (G: χ2 = 4.05, P = 0.0441; C: χ2 = 3.96, P = 0.0465).
Figure 4
Figure 4
Relationship between nesting location, percentage of clutches sired by multiple males, and the average number of fathers per clutch by location. Adapted using data from Moore and Ball and Zbinden et al. .

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