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

• Published in: Journal of evolutionary biology 2019-10, Vol.32 (10), p.1152-1162
• Main Authors: Yuan, Michael L., White, K. Nicole, Rothermel, Betsie B., Zamudio, Kelly R., Tuberville, Tracey D.
• Format: Article
• Language: English
• Subjects: Avoidance; Biological evolution; Breeding; conservation genetics; Evolution; Females; gopher tortoise; Gopherus polyphemus; Hatching; Inbreeding; inbreeding avoidance; Inbreeding depression; Males; Mating behavior; mating system; microsatellite; Natural populations; Offspring; Population decline; Population studies; Populations; relatedness; reproductive success; Threatened species; Tortoises; Wildlife conservation
• ISSN: 1010-061X; 1420-9101
• DOI: 10.1111/jeb.13518

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. Hatchling gopher tortoise, Gopherus polyphemus. Egg viability and hatchling quality are reduced when parents are closely‐related. However, highly inbred mothers have fitter offspring and greater clutch viability, perhaps because highly inbred females tend to mate with more distantly‐related males.