SREL Reprint #3519

Close-kin mating, but not inbred parents, reduces hatching rates and offspring quality in a threatened tortoise

Michael L. Yuan1,2, K. Nicole White2,3,4, Betsie B. Rothermel2, Kelly R. Zamudio5,
and Tracey D. Tuberville3

1Department of Environmental Science, Policy, and Management, College of Natural Resources,
University of California, Berkeley, CA, USA
2Archbold Biological Station, Venus, FL, USA
3Savannah River Ecology Laboratory, University of Georgia, Aiken, SC, USA
4Daniel B. Warnell School of Forestry and Natural Resources, University of Georgia, Athens, GA, USA
5Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY, USA

Abstract: Inbreeding depression, the reduction in fitness due to mating of related individuals, is of particular conservation concern in species with small, isolated populations. Although inbreeding depression is widespread in natural populations, long-lived species may be buffered from its effects during population declines due to long generation times and thus are less likely to have evolved mechanisms of inbreeding avoidance than species with shorter generation times. However, empirical evidence of the consequences of inbreeding in threatened, long-lived species is limited. In this study, we leverage a well-studied population of gopher tortoises, Gopherus polyphemus, to examine the role of inbreeding depression and the potential for behavioural inbreeding avoidance in a natural population of a long-lived species. We tested the hypothesis that increased parental inbreeding leads to reduced hatching rates and offspring quality. Additionally, we tested for evidence of inbreeding avoidance. We found that high parental relatedness results in offspring with lower quality and that high parental relatedness is correlated with reduced hatching success. However, we found that hatching success and offspring quality increase with maternal inbreeding, likely due to highly inbred females mating with more distantly related males. We did not find evidence for inbreeding avoidance in males and outbred females, suggesting sex-specific evolutionary trade-offs may have driven the evolution of mating behaviour. Our results demonstrate inbreeding depression in a long-lived species and that the evolution of inbreeding avoidance is shaped by multiple selective forces.

Keywords: conservation genetics, gopher tortoise, Gopherus polyphemus, inbreeding avoidance, mating system, microsatellite, relatedness, reproductive success

SREL Reprint #3519

Yuan, M. L., K. N. White, B. B. Rothermel, K. R. Zamudio, and T. D. Tuberville. 2019. Close-kin mating, but not inbred parents, reduces hatching rates and offspring quality in a threatened tortoise. Journal of Evolutionary Biology 2019(32): 1152-1162.

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