Life history data for: High investment into reproduction is associated with reduced lifespan in dogs

Prominent differences in aging among and within species present an evolutionary puzzle. The theories proposed to explain evolutionary differences in aging are based on the axiom that selection maximizes fitness, not necessarily lifespan. This implies trade-offs between investment into self-maintenance and investment into reproduction, where high investment into growth and current reproduction are associated with short lifespans. Fast growth and large adult size are related with shorter lifespans in the domestic dog, a bourgeoning model in aging research, however, whether reproduction influences lifespan in this system remains unknown. Here we test the relationship between reproduction and differences in lifespan among dog breeds, controlling simultaneously for shared ancestry and recent gene flow. We found that shared ancestry explains a higher proportion of the among-breed variation in life history traits, in comparison with recent gene flow. Our results also show that reproductive investment negatively impacts lifespan, and more strongly so in large breeds, an effect that is not merely a correlated response of adult size. These results suggest that basic life history trade-offs are apparent in a domestic animal whose diversity is the result of artificial selection and that among-breed differences in lifespan are due to a combination of size and reproduction.

物种间与物种内部衰老进程的显著差异，始终是演化生物学领域的一道难解谜题。现有用以阐释衰老演化差异的理论，均基于一条核心公理：自然选择的目标是最大化适合度（fitness），而非必然延长个体寿命。这意味着机体自我维持投入与繁殖投入之间存在权衡取舍（trade-off），即生长与当前繁殖的高投入往往与较短的寿命相关联。作为衰老研究领域的新兴模式生物，家犬（domestic dog）的快速生长与较大成体体型均与较短寿命存在关联；然而在该体系中，繁殖是否会对寿命产生影响仍未可知。本研究针对犬品种间寿命差异与繁殖的关联展开检验，同时控制了共同祖先（shared ancestry）与近期基因流（recent gene flow）的影响。研究结果显示，相较于近期基因流，共同祖先能够解释更多犬品种间生活史性状（life history traits）的变异量。本研究同时发现，繁殖投入（reproductive investment）会对寿命产生负面影响，且在体型较大的犬品种中这一效应更为显著——该效应并非仅仅由成体体型的相关响应所导致。上述结果表明，基本的生活史权衡取舍在这一由人工选择造就多样性的家养动物中清晰可见，而犬品种间的寿命差异，乃是体型与繁殖共同作用的结果。