Evolutionary history and life-history traits influence cause-specific mortality in domestic dogs

A fruitful avenue to understand differences in lifespan is to study the factors driving differences in intrinsic mortality, such as disease. The domestic dog is an emerging model in longevity research and presents an unrivalled opportunity to analyse the effects of life history and evolutionary history on variation in vulnerability to diseases causing mortality. We analysed cause-specific mortality-categorized by the organ system affected and by pathophysiological process-across 72 dog breeds using Bayesian multinomial models. We first analysed the influence of evolutionary history (common ancestry and hybridization events) on among-breed variation in specific causes of death. We then tested the association between life-history traits and specific causes of death, controlling for non-independence due to common ancestry and hybridization. We found differences in the proportion of variance explained by common ancestry and hybridization across causes of death; mortality due to musculoskeletal and neoplastic processes exhibited the strongest genetic influence, while gastrointestinal and metabolic causes showed the weakest. Increased body size was associated with higher mortality from musculoskeletal, haematopoietic, and gastrointestinal causes, and with lower mortality from endocrine and urogenital causes. Higher reproductive investment was associated with lower mortality from congenital, degenerative, and inflammatory causes. Finally, we found a negative association between trainability and mortality due to infectious causes. These findings suggest that specific causes of death in dogs are shaped by both evolutionary history and trade-offs associated with life-history traits, underscoring the importance of incorporating genetic relatedness and evolutionary theory into the study of disease vulnerability in domesticated animals.