SREL Reprint #3479

Male body size predicts reproductive success but not within-clutch paternity patterns in gopher tortoises (Gopherus polyphemus)

K. Nicole White1,2,3, Betsie B. Rothermel3, Kelly R. Zamudio4, and Tracey D. Tuberville1

1Savannah River Ecology Laboratory, University of Georgia, PO Drawer E, Aiken, SC 29802
2Daniel B. Warnell School of Forestry and Natural Resources, University of Georgia,
180 E Green Street, Athens, GA 30602
3Archbold Biological Station, 123 Main Drive, Venus, FL 33960
4Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY 14853

Abstract: In many vertebrates, body size is an important driver of variation in male reproductive success. Larger, more fit individuals are more likely to dominate mating opportunities, skewing siring success and resulting in lower effective population sizes and genetic diversity. The mating system of the gopher tortoise (Gopherus polyphemus) has been characterized as both female-defense and scramble-competition polygyny. Mating systems are typically not fixed and can be influenced by factors such as population density, demographic structure, and environmental conditions; however, most populations will have a predominant strategy that results from local conditions. We assessed how male body size influences patterns of paternity and reproductive success in a natural population of gopher tortoises in Florida, United States. Using microsatellites, we assigned parentage of 220 hatchlings from 31 nests collected during 2 reproductive seasons. Larger males were significantly more likely to sire offspring and sired more offspring than smaller males; however, the likelihood of a clutch being multiply sired was unrelated to male body size. We also found evidence of mate fidelity across years. Although paternity patterns in this high-density population are more consistent with defense polygyny, female monopoly by males was incomplete, with both large and small males contributing to multiply sired clutches. Additional behavioral data are needed to clarify the role of female mate selection in paternity outcomes. The context-dependence of mating systems underscores the need to compare parentage patterns across populations and to recognize the potential for more than 1 strategy to be employed within a single population.

Keywords: body size, Gopherus polyphemus, mating system, microsatellites, reproductive success

SREL Reprint #3479

White, K. N., B. B. Rothermel, K. R. Zamudio, and T. D. Tuberville. 2018. Male body size predicts reproductive success but not within-clutch paternity patterns in gopher tortoises (Gopherus polyphemus). Journal of Heredity 109(7): 791-801.

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).